Deviations from the average or standard indices of refraction of the eye through its dioptric or refractive apparatus.
A refractive error in which rays of light entering the EYE parallel to the optic axis are brought to a focus in front of the RETINA when accommodation (ACCOMMODATION, OCULAR) is relaxed. This results from an overly curved CORNEA or from the eyeball being too long from front to back. It is also called nearsightedness.
A refractive error in which rays of light entering the eye parallel to the optic axis are brought to a focus behind the retina, as a result of the eyeball being too short from front to back. It is also called farsightedness because the near point is more distant than it is in emmetropia with an equal amplitude of accommodation. (Dorland, 27th ed)
Refraction of LIGHT effected by the media of the EYE.
A pair of ophthalmic lenses in a frame or mounting which is supported by the nose and ears. The purpose is to aid or improve vision. It does not include goggles or nonprescription sun glasses for which EYE PROTECTIVE DEVICES is available.
An objective determination of the refractive state of the eye (NEARSIGHTEDNESS; FARSIGHTEDNESS; ASTIGMATISM). By using a RETINOSCOPE, the amount of correction and the power of lens needed can be determined.
Unequal curvature of the refractive surfaces of the eye. Thus a point source of light cannot be brought to a point focus on the retina but is spread over a more or less diffuse area. This results from the radius of curvature in one plane being longer or shorter than the radius at right angles to it. (Dorland, 27th ed)
The dioptric adjustment of the EYE (to attain maximal sharpness of retinal imagery for an object of regard) referring to the ability, to the mechanism, or to the process. Ocular accommodation is the effecting of refractive changes by changes in the shape of the CRYSTALLINE LENS. Loosely, it refers to ocular adjustments for VISION, OCULAR at various distances. (Cline et al., Dictionary of Visual Science, 4th ed)
Application of tests and examinations to identify visual defects or vision disorders occurring in specific populations, as in school children, the elderly, etc. It is differentiated from VISION TESTS, which are given to evaluate/measure individual visual performance not related to a specific population.
Clarity or sharpness of OCULAR VISION or the ability of the eye to see fine details. Visual acuity depends on the functions of RETINA, neuronal transmission, and the interpretative ability of the brain. Normal visual acuity is expressed as 20/20 indicating that one can see at 20 feet what should normally be seen at that distance. Visual acuity can also be influenced by brightness, color, and contrast.
The distance between the anterior and posterior poles of the eye, measured either by ULTRASONOGRAPHY or by partial coherence interferometry.
The condition of where images are correctly brought to a focus on the retina.
A condition of an inequality of refractive power of the two eyes.
The use of statistical and mathematical methods to analyze biological observations and phenomena.
The organ of sight constituting a pair of globular organs made up of a three-layered roughly spherical structure specialized for receiving and responding to light.
Agents that dilate the pupil. They may be either sympathomimetics or parasympatholytics.
Misalignment of the visual axes of the eyes. In comitant strabismus the degree of ocular misalignment does not vary with the direction of gaze. In noncomitant strabismus the degree of misalignment varies depending on direction of gaze or which eye is fixating on the target. (Miller, Walsh & Hoyt's Clinical Neuro-Ophthalmology, 4th ed, p641)
A series of tests used to assess various functions of the eyes.
A nonspecific term referring to impaired vision. Major subcategories include stimulus deprivation-induced amblyopia and toxic amblyopia. Stimulus deprivation-induced amblyopia is a developmental disorder of the visual cortex. A discrepancy between visual information received by the visual cortex from each eye results in abnormal cortical development. STRABISMUS and REFRACTIVE ERRORS may cause this condition. Toxic amblyopia is a disorder of the OPTIC NERVE which is associated with ALCOHOLISM, tobacco SMOKING, and other toxins and as an adverse effect of the use of some medications.
A parasympatholytic anticholinergic used solely to obtain mydriasis or cycloplegia.
Persons with loss of vision such that there is an impact on activities of daily living.
Vision considered to be inferior to normal vision as represented by accepted standards of acuity, field of vision, or motility. Low vision generally refers to visual disorders that are caused by diseases that cannot be corrected by refraction (e.g., MACULAR DEGENERATION; RETINITIS PIGMENTOSA; DIABETIC RETINOPATHY, etc.).
The professional practice of primary eye and vision care that includes the measurement of visual refractive power and the correction of visual defects with lenses or glasses.
The normal decreasing elasticity of the crystalline lens that leads to loss of accommodation.
Surgical procedures employed to correct REFRACTIVE ERRORS such as MYOPIA; HYPEROPIA; or ASTIGMATISM. These may involve altering the curvature of the CORNEA; removal or replacement of the CRYSTALLINE LENS; or modification of the SCLERA to change the axial length of the eye.
Visual impairments limiting one or more of the basic functions of the eye: visual acuity, dark adaptation, color vision, or peripheral vision. These may result from EYE DISEASES; OPTIC NERVE DISEASES; VISUAL PATHWAY diseases; OCCIPITAL LOBE diseases; OCULAR MOTILITY DISORDERS; and other conditions (From Newell, Ophthalmology: Principles and Concepts, 7th ed, p132).
Diseases affecting the eye.
The measurement of curvature and shape of the anterior surface of the cornea using techniques such as keratometry, keratoscopy, photokeratoscopy, profile photography, computer-assisted image processing and videokeratography. This measurement is often applied in the fitting of contact lenses and in diagnosing corneal diseases or corneal changes including keratoconus, which occur after keratotomy and keratoplasty.
The absence or restriction of the usual external sensory stimuli to which the individual responds.
The aperture in the iris through which light passes.
I'm sorry for any confusion, but "Singapore" is not a medical term or concept, it's a country in Southeast Asia. If you have any questions about medical topics, I'd be happy to try and help!
A form of ocular misalignment characterized by an excessive convergence of the visual axes, resulting in a "cross-eye" appearance. An example of this condition occurs when paralysis of the lateral rectus muscle causes an abnormal inward deviation of one eye on attempted gaze.
The space in the eye, filled with aqueous humor, bounded anteriorly by the cornea and a small portion of the sclera and posteriorly by a small portion of the ciliary body, the iris, and that part of the crystalline lens which presents through the pupil. (Cline et al., Dictionary of Visual Science, 4th ed, p109)
Pieces of glass or other transparent materials used for magnification or increased visual acuity.
The inability to see or the loss or absence of perception of visual stimuli. This condition may be the result of EYE DISEASES; OPTIC NERVE DISEASES; OPTIC CHIASM diseases; or BRAIN DISEASES affecting the VISUAL PATHWAYS or OCCIPITAL LOBE.
Lenses designed to be worn on the front surface of the eyeball. (UMDNS, 1999)
The transparent anterior portion of the fibrous coat of the eye consisting of five layers: stratified squamous CORNEAL EPITHELIUM; BOWMAN MEMBRANE; CORNEAL STROMA; DESCEMET MEMBRANE; and mesenchymal CORNEAL ENDOTHELIUM. It serves as the first refracting medium of the eye. It is structurally continuous with the SCLERA, avascular, receiving its nourishment by permeation through spaces between the lamellae, and is innervated by the ophthalmic division of the TRIGEMINAL NERVE via the ciliary nerves and those of the surrounding conjunctiva which together form plexuses. (Cline et al., Dictionary of Visual Science, 4th ed)
The total number of cases of a given disease in a specified population at a designated time. It is differentiated from INCIDENCE, which refers to the number of new cases in the population at a given time.
The use of an aberrometer to measure eye tissue imperfections or abnormalities based on the way light passes through the eye which affects the ability of the eye to focus properly.
Partial or complete opacity on or in the lens or capsule of one or both eyes, impairing vision or causing blindness. The many kinds of cataract are classified by their morphology (size, shape, location) or etiology (cause and time of occurrence). (Dorland, 27th ed)
Excessive axial myopia associated with complications (especially posterior staphyloma and CHOROIDAL NEOVASCULARIZATION) that can lead to BLINDNESS.
A surgical procedure to correct MYOPIA by CORNEAL STROMA subtraction. It involves the use of a microkeratome to make a lamellar dissection of the CORNEA creating a flap with intact CORNEAL EPITHELIUM. After the flap is lifted, the underlying midstroma is reshaped with an EXCIMER LASER and the flap is returned to its original position.
A procedure to surgically correct REFRACTIVE ERRORS by cutting radial slits into the CORNEA to change its refractive properties.
A transparent, biconvex structure of the EYE, enclosed in a capsule and situated behind the IRIS and in front of the vitreous humor (VITREOUS BODY). It is slightly overlapped at its margin by the ciliary processes. Adaptation by the CILIARY BODY is crucial for OCULAR ACCOMMODATION.
Measurement of distances or movements by means of the phenomena caused by the interference of two rays of light (optical interferometry) or of sound (acoustic interferometry).
A type of refractive surgery of the CORNEA to correct MYOPIA and ASTIGMATISM. An EXCIMER LASER is used directly on the surface of the EYE to remove some of the CORNEAL EPITHELIUM thus reshaping the anterior curvature of the cornea.
A country in Southeastern Asia, northwest of Australia in the Lesser Sunda Islands at the eastern end of the Indonesian archipelago. It includes the eastern half of the island of Timor, the Oecussi (Ambeno) region on the northwest portion of the island of Timor, and the islands of Pulau Atauro and Pulau Jaco. On May 20, 2002, East Timor was internationally recognized as an independent state. This followed its declared independence from Portugal on November 20, 1975 and a period of armed conflict with Indonesia.
Gas lasers with excited dimers (i.e., excimers) as the active medium. The most commonly used are rare gas monohalides (e.g., argon fluoride, xenon chloride). Their principal emission wavelengths are in the ultraviolet range and depend on the monohalide used (e.g., 193 nm for ArF, 308 nm for Xe Cl). These lasers are operated in pulsed and Q-switched modes and used in photoablative decomposition involving actual removal of tissue. (UMDNS, 2005)
Insertion of an artificial lens to replace the natural CRYSTALLINE LENS after CATARACT EXTRACTION or to supplement the natural lens which is left in place.
The frequency of different ages or age groups in a given population. The distribution may refer to either how many or what proportion of the group. The population is usually patients with a specific disease but the concept is not restricted to humans and is not restricted to medicine.
A form of ocular misalignment where the visual axes diverge inappropriately. For example, medial rectus muscle weakness may produce this condition as the affected eye will deviate laterally upon attempted forward gaze. An exotropia occurs due to the relatively unopposed force exerted on the eye by the lateral rectus muscle, which pulls the eye in an outward direction.
The transparent, semigelatinous substance that fills the cavity behind the CRYSTALLINE LENS of the EYE and in front of the RETINA. It is contained in a thin hyaloid membrane and forms about four fifths of the optic globe.
## I'm sorry for any confusion, but there seems to be a misunderstanding as "Belize" is a country located in Central America and not a medical term. It is always important to ensure the accuracy of terminology, particularly in medical contexts.
Individuals whose ancestral origins are in the southeastern and eastern areas of the Asian continent.
The number of males and females in a given population. The distribution may refer to how many men or women or what proportion of either in the group. The population is usually patients with a specific disease but the concept is not restricted to humans and is not restricted to medicine.
Incorrect diagnoses after clinical examination or technical diagnostic procedures.
Albinism affecting the eye in which pigment of the hair and skin is normal or only slightly diluted. The classic type is X-linked (Nettleship-Falls), but an autosomal recessive form also exists. Ocular abnormalities may include reduced pigmentation of the iris, nystagmus, photophobia, strabismus, and decreased visual acuity.
Methods and procedures for the diagnosis of diseases of the eye or of vision disorders.
One of the MUSCARINIC ANTAGONISTS with pharmacologic action similar to ATROPINE and used mainly as an ophthalmic parasympatholytic or mydriatic.
The process in which light signals are transformed by the PHOTORECEPTOR CELLS into electrical signals which can then be transmitted to the brain.
A specialized field of physics and engineering involved in studying the behavior and properties of light and the technology of analyzing, generating, transmitting, and manipulating ELECTROMAGNETIC RADIATION in the visible, infrared, and ultraviolet range.
Studies in which the presence or absence of disease or other health-related variables are determined in each member of the study population or in a representative sample at one particular time. This contrasts with LONGITUDINAL STUDIES which are followed over a period of time.
The thin, highly vascular membrane covering most of the posterior of the eye between the RETINA and SCLERA.
I'm sorry for any confusion, but "India" is not a medical term that can be defined in a medical context. It is a geographical location, referring to the Republic of India, a country in South Asia. If you have any questions related to medical topics or definitions, I would be happy to help with those!
Soft, supple contact lenses made of plastic polymers which interact readily with water molecules. Many types are available, including continuous and extended-wear versions, which are gas-permeable and easily sterilized.
An imaging method using LASERS that is used for mapping subsurface structure. When a reflective site in the sample is at the same optical path length (coherence) as the reference mirror, the detector observes interference fringes.
Method of making images on a sensitized surface by exposure to light or other radiant energy.
Measurement of the index of refraction (the ratio of the velocity of light or other radiation in the first of two media to its velocity in the second as it passes from one into the other).
A surgical specialty concerned with the structure and function of the eye and the medical and surgical treatment of its defects and diseases.
A bilateral retinopathy occurring in premature infants treated with excessively high concentrations of oxygen, characterized by vascular dilatation, proliferation, and tortuosity, edema, and retinal detachment, with ultimate conversion of the retina into a fibrous mass that can be seen as a dense retrolental membrane. Usually growth of the eye is arrested and may result in microophthalmia, and blindness may occur. (Dorland, 27th ed)
The turning inward of the lines of sight toward each other.
A visual symptom in which a single object is perceived by the visual cortex as two objects rather than one. Disorders associated with this condition include REFRACTIVE ERRORS; STRABISMUS; OCULOMOTOR NERVE DISEASES; TROCHLEAR NERVE DISEASES; ABDUCENS NERVE DISEASES; and diseases of the BRAIN STEM and OCCIPITAL LOBE.
Images seen by one eye.
Processes and properties of the EYE as a whole or of any of its parts.
The removal of a cataractous CRYSTALLINE LENS from the eye.
The inhabitants of a city or town, including metropolitan areas and suburban areas.
I'm sorry for any confusion, but "Arizona" is a proper noun and refers to a state in the southwestern United States, not a medical term or condition. It would not have a medical definition.
The blending of separate images seen by each eye into one composite image.
Presence of an intraocular lens after cataract extraction.
An area approximately 1.5 millimeters in diameter within the macula lutea where the retina thins out greatly because of the oblique shifting of all layers except the pigment epithelium layer. It includes the sloping walls of the fovea (clivus) and contains a few rods in its periphery. In its center (foveola) are the cones most adapted to yield high visual acuity, each cone being connected to only one ganglion cell. (Cline et al., Dictionary of Visual Science, 4th ed)
The statistical reproducibility of measurements (often in a clinical context), including the testing of instrumentation or techniques to obtain reproducible results. The concept includes reproducibility of physiological measurements, which may be used to develop rules to assess probability or prognosis, or response to a stimulus; reproducibility of occurrence of a condition; and reproducibility of experimental results.
A procedure for removal of the crystalline lens in cataract surgery in which an anterior capsulectomy is performed by means of a needle inserted through a small incision at the temporal limbus, allowing the lens contents to fall through the dilated pupil into the anterior chamber where they are broken up by the use of ultrasound and aspirated out of the eye through the incision. (Cline, et al., Dictionary of Visual Science, 4th ed & In Focus 1993;1(1):1)
The pressure of the fluids in the eye.
Nystagmus present at birth or caused by lesions sustained in utero or at the time of birth. It is usually pendular, and is associated with ALBINISM and conditions characterized by early loss of central vision. Inheritance patterns may be X-linked, autosomal dominant, or recessive. (Adams et al., Principles of Neurology, 6th ed, p275)
General disorders of the sclera or white of the eye. They may include anatomic, embryologic, degenerative, or pigmentation defects.
An ocular disease, occurring in many forms, having as its primary characteristics an unstable or a sustained increase in the intraocular pressure which the eye cannot withstand without damage to its structure or impairment of its function. The consequences of the increased pressure may be manifested in a variety of symptoms, depending upon type and severity, such as excavation of the optic disk, hardness of the eyeball, corneal anesthesia, reduced visual acuity, seeing of colored halos around lights, disturbed dark adaptation, visual field defects, and headaches. (Dictionary of Visual Science, 4th ed)
The portion of the optic nerve seen in the fundus with the ophthalmoscope. It is formed by the meeting of all the retinal ganglion cell axons as they enter the optic nerve.
Artificial implanted lenses.
Perception of three-dimensionality.
(LA) is not a medical term; it is a region, specifically the second most populous city in the United States, located in Southern California, which contains several world-renowned hospitals and medical centers that offer advanced healthcare services and cutting-edge medical research.
Measuring and weighing systems and processes.
Absence of the crystalline lens resulting from cataract extraction.
The ten-layered nervous tissue membrane of the eye. It is continuous with the OPTIC NERVE and receives images of external objects and transmits visual impulses to the brain. Its outer surface is in contact with the CHOROID and the inner surface with the VITREOUS BODY. The outer-most layer is pigmented, whereas the inner nine layers are transparent.
The inhabitants of rural areas or of small towns classified as rural.
Heterogeneous group of autosomal recessive disorders comprising at least four recognized types, all having in common varying degrees of hypopigmentation of the skin, hair, and eyes. The two most common are the tyrosinase-positive and tyrosinase-negative types.
The white, opaque, fibrous, outer tunic of the eyeball, covering it entirely excepting the segment covered anteriorly by the cornea. It is essentially avascular but contains apertures for vessels, lymphatics, and nerves. It receives the tendons of insertion of the extraocular muscles and at the corneoscleral junction contains the canal of Schlemm. (From Cline et al., Dictionary of Visual Science, 4th ed)
A characteristic showing quantitative inheritance such as SKIN PIGMENTATION in humans. (From A Dictionary of Genetics, 4th ed)
A noninflammatory, usually bilateral protrusion of the cornea, the apex being displaced downward and nasally. It occurs most commonly in females at about puberty. The cause is unknown but hereditary factors may play a role. The -conus refers to the cone shape of the corneal protrusion. (From Dorland, 27th ed)
Methods of detecting genetic etiology in human traits. The basic premise of twin studies is that monozygotic twins, being formed by the division of a single fertilized ovum, carry identical genes, while dizygotic twins, being formed by the fertilization of two ova by two different spermatozoa, are genetically no more similar than two siblings born after separate pregnancies. (Last, J.M., A Dictionary of Epidemiology, 2d ed)

Results of small incision extracapsular cataract surgery using the anterior chamber maintainer without viscoelastic. (1/740)

AIMS: To assess the efficacy of extracapsular cataract surgery using the anterior chamber maintainer (ACM) without the use of viscoelastic. To compare the effects of this surgical technique on non-diabetic and diabetic patients. METHODS: A prospective single armed clinical trial of 46 eyes in 46 patients undergoing cataract surgery using the ACM without viscoelastic. Patients were assessed preoperatively and at 3 weeks, 3 months, and 12 months postoperatively. The main outcome variables included visual acuity, surgically induced astigmatic change (SIAC), changes in endothelial cell density (ECD), and morphology affecting the central and superior regions of the cornea. RESULTS: Postoperatively, 56% and 70% of patients had unaided visual acuities of 6/12 or better at 3 weeks and 3 months respectively. Even after excluding those patients with pre-existing maculopathy (including diabetic maculopathy), there remains a significant difference between the non-diabetic and diabetic groups in terms of the proportion of patients attaining an unaided visual acuity of 6/12 or better at both 3 weeks (p = 0.003) and 3 months (p = 0.001). Three months postoperatively, the SIAC based upon the keratometric and refractive data was 1.1 dioptres (D) and 1.3 D respectively. There was no statistically significant difference in the SIAC when the non-diabetic and diabetic groups were compared. The mean central and superior endothelial cell losses at 3 months postoperatively were 16% and 22% respectively and at 12 months postoperatively were 20% and 25% respectively. The diabetic group demonstrated greater endothelial cell losses and a more marked and protracted deviation of endothelial cell morphology from normality when compared with the non-diabetic group; however, the differences did not reach statistical significance. CONCLUSIONS: The efficacy of small incision cataract surgery using the ACM in terms of visual outcome and induced astigmatism is comparable with the results obtained using other techniques that utilise a similar size of incision. However, in view of the magnitude and range of the endothelial cell losses associated with this technique the concurrent use of viscoelastic is suggested. There does not appear to be a statistically or clinically significant difference between non-diabetic and diabetic patients in terms of the magnitude of the endothelial cell losses or in the wound healing response in the 12 months after cataract surgery using the ACM.  (+info)

Tonic accommodation, age, and refractive error in children. (2/740)

PURPOSE: An association between tonic accommodation, the resting accommodative position of the eye in the absence of a visually compelling stimulus, and refractive error has been reported in adults and children. In general, myopes have the lowest (or least myopic) levels of tonic accommodation. The purpose in assessing tonic accommodation was to evaluate it as a predictor of onset of myopia. METHODS: Tonic accommodation was measured in children enrolled in the Orinda Longitudinal Study of Myopia using an infrared autorefractor (model R-1; Canon, Lake Success, NY) while children viewed an empty lit field or a dark field with a fixation spot projected in Maxwellian view. Children aged 6 to 15 years were measured from 1991 through 1994 (n = 714, 766, 771, and 790 during the 4 years, successively). Autorefraction provided refractive error and tonic accommodation data, and videophakometry measured crystalline lens curvatures. RESULTS: Comparison of the two methods for measuring tonic accommodation shows a significant effect of age across all years of testing, with the lit empty-field test condition yielding higher levels of tonic accommodation compared with the dark-field test condition in children aged 6 through 11 years. For data collected in 1994, mean (+/-SD) tonic accommodation values for the lit empty-field condition were significantly lower in myopes, intermediate in emmetropes, and highest in hyperopes (1.02 +/- 1.18 D, 1.92 +/- 1.59 D, and 2.25 +/- 1.78 D, respectively; Kruskal-Wallis test, P < 0.001; between-group testing shows each group is different from the other two). Age, refractive error, and Gullstrand lens power were significant terms in a multiple regression model of tonic accommodation (R2 = 0.18 for 1994 data). Lower levels of tonic accommodation for children entering the study in the first or third grades were not associated with an increased risk of the onset of myopia, whether measured in the lit empty-field test condition (relative risk = 0.90; 95% confidence interval = 0.75, 1.08), or the dark-field test condition (relative risk = 0.83; 95% confidence interval = 0.60, 1.14). CONCLUSIONS: This is the first study to document an association between age and tonic accommodation. The known association between tonic accommodation and refractive error was confirmed and it was shown that an ocular component, Gullstrand lens power, also contributed to the tonic accommodation level. There does not seem to be an increased risk of onset of juvenile myopia associated with tonic accommodation.  (+info)

The effects of spectacle wear in infancy on eye growth and refractive error in the marmoset (Callithrix jacchus). (3/740)

We made a comprehensive study, involving observations on 45 marmosets, of the effects on ocular growth and refraction of wearing spectacles from the ages of 4-8 weeks. This period was within the period early in life when the eye grows rapidly and refraction changes from hyperopia to its adult value of modest myopia. In one series of experiments we studied the effect of lenses of powers -8, -4, +4 and +8D fitted monocularly. In another series of experiments we studied the effect of lenses of equal and opposite powers fitted binocularly, with the two eyes alternately occluded, so as to give an incentive to use both eyes, and in particular to accommodate, for at least part of each day, through the negative lens. The vitreous chamber of eyes that wore negative lenses of -4D or -8D, combined with alternate occlusion, elongated more rapidly than that of the fellow eye (negative lens eye-positive lens eye, 0.21 +/- 0.03 mm (S.E.M.), P < 0.01 and 0.25 +/- 0.06 mm, P < 0.05, respectively) and became relatively more myopic (2.8 +/- 0.26D, P < 0.01 and 2.4 +/- 0.61D, P < 0.05 respectively). Eyes that wore -4D lenses monocularly elongated more rapidly and became myopic than fellow eyes. Eyes that wore +4D or +8D lenses were less strongly affected: animals that wore +8D lenses monocularly (without alternate occlusion) developed a slight relative hyperopia (0.99 +/- 0.21D, P < 0.01), with the more hyperopic eyes also slightly shorter (0.09 +/- 0.05 mm) than their fellow eyes, but eyes wearing +4D lenses were not significantly different from their fellow eyes. Animals that wore -8D lenses monocularly (without alternate occlusion) developed a slight relative hyperopia after three weeks of lens-wear (0.85 +/- 0.26D, P < 0.05). These were the only eyes that responded in a non-compensatory direction to the optical challenge of spectacle wear, and we interpret this effect as one due to visual deprivation. After the removal of lenses, the degree of anisometropia slowly diminished in those groups of animals in which it had been induced, but in the three groups in which the largest effects had been produced by lens-wear the overall mean anisometropia (0.68 +/- 0.24D, P < 0.01) and vitreous chamber depth (VCD) discrepancy (0.09 +/- 0.03 mm, P < 0.01) were still significant at the end of the experiments, when the animals were 273 days old. The reduction of anisometropia in these groups was associated with an increase in the rate of elongation of the vitreous chamber in the eyes that had previously grown normally i.e. the less myopic eyes grew more rapidly than their fellow eyes: in the seven weeks following lens-wear these eyes became more myopic and longer than normal eyes (refraction P < 0.001; VCD P < 0.001). Control experiments showed that occlusion of one eye for 50% of the day had no effect on eye growth and refraction, and therefore that alternate occlusion itself had no effect.  (+info)

Off-axis monochromatic aberrations estimated from double pass measurements in the human eye. (4/740)

Off-axis monochromatic aberrations in the human eye impose limits on peripheral vision. However, the magnitude of the aberrations off-axis, and in particular coma, has not been yet completely determined. We have developed a procedure to estimate third order aberrations in the periphery of the human eye. The technique is based on recording series of double pass retinal images with unequal entrance and exit pupil diameters (Artal, Iglesias, Lopez-Gil & Green (1995b). J. Opt. Soc. Am. A, 12, 2358-2366.) which allows the odd asymmetries in the retinal image be assessed. The procedure that is described provides accurate estimates of the main off-axis aberrations: astigmatism, defocus and coma. We have measured these aberrations in four normal subjects. For a given eccentricity, the measured amount of coma and astigmatism are relatively similar among subjects, because the angular distance from the axis is the dominant factor in determining the magnitude of these aberrations. However, we found considerable variability in the values of peripheral defocus, probably due to a complicate combination of off-axis aberrations and fundus shape. The final off-axis optical performance of the eye for a given object location is determined by a particular mixture of defocus, astigmatism, coma and higher order aberrations.  (+info)

Abnormal tear dynamics and symptoms of eyestrain in operators of visual display terminals. (5/740)

OBJECTIVES: To clarify the relation between the prevalence of dry eye syndrome and subjective symptoms of asthenopia in visual display terminal (VDT) operators. METHOD: 722 VDT workers (242 subject workers with symptoms of asthenopia and 480 controls without such symptoms) without obvious organic ocular diseases received an ophthalmological examination consisting of refractometry and a tear function (phenol red thread) test. RESULTS: More than 30% of symptomatic workers were found to meet the criteria of dry eye, and the odds ratio compared with the controls was 4.61 (p < 0.001). This odds ratio was significantly greater than that obtained for refractive errors (2.31). CONCLUSIONS: Although this cross sectional study could not prove that dry eyes are the cause of asthenopia, the profound association of dry eyes with symptoms of asthenopia could be verified. It would be useful to carry out tear function tests in workers with symptoms of asthenopia.  (+info)

Changes in refractive error over a 5-year interval in the Beaver Dam Eye Study. (6/740)

PURPOSE: To examine changes in spherical equivalent over a 5-year period in persons 43 to 84 years of age. METHODS: All people 43 to 84 years of age and living in Beaver Dam, Wisconsin, in 1988 were invited for a baseline examination (1988-1990) and a 5-year follow-up examination (1993-1995). Refractions were determined according to the same protocol at both examinations. Aphakic and pseudophakic eyes were excluded as well as eyes with best corrected Snellen visual acuity of 20/40 and worse. After exclusions, refraction was obtained on 3007 right eyes and 3012 left eyes of the 3684 people participating in both examinations. RESULTS: Right and left eyes behaved similarly. Spherical equivalent became more positive in the youngest subjects and more negative in older subjects. After adjusting for other factors, the 5-year change in spherical equivalent of those 45, 55, 65, and 75 years of age was +0.15, +0.18, +0.10, and -0.07D, respectively. Severity of nuclear sclerosis was related to the amount of change. Those with mild nuclear sclerosis at baseline had a change of +0.2 D, whereas those with severe nuclear sclerosis had a change of -0.5 D. The amount of change was also related to gender, diabetes, and age at onset of myopia. It was unrelated to education and baseline spherical equivalent. CONCLUSIONS: Changes in spherical equivalent over a 5-year period were small. Before the age of 70, people became more hyperopic. After the age of 70, people became more myopic. Much of the myopic change may be related to increasing nuclear sclerosis.  (+info)

Amblyopia and visual acuity in children with Down's syndrome. (7/740)

BACKGROUND/AIMS: Amblyopia in people with Down's syndrome has not been well investigated. This study was designed to determine the prevalence and associated conditions of amblyopia in a group of home reared children with Down's syndrome. METHODS: All children in the study group underwent an evaluation of visual acuity. In addition, previous ophthalmological records were reviewed, and a subgroup of children was examined. For the purposes of this study, amblyopia was defined quantitatively as a difference of two Snellen acuity lines between eyes or if unilateral central steady maintained (CSM) vision and a clear fixation preference was observed. A high refractive error was defined as a spherical equivalent more than 3 dioptres and astigmatism more than 1.75 dioptres. Anisometropia was defined as a difference of at least 1.5 dioptres of sphere and/or 1.0 dioptre of cylinder between eyes. 68 children with Down's syndrome between the ages of 5 and 19 years were enrolled in the final study group. RESULTS: Amblyopia was observed in 15 (22%) of 68 patients. An additional 16 (24%) patients had bilateral vision less than 20/50. Strabismus, high refractive errors, and anisometropia were the conditions most commonly associated with decreased vision and amblyopia CONCLUSION: This study suggests that the prevalence of amblyopia is higher than previously reported. Fully 46% of these children with Down's syndrome had evidence of substantial visual deficits. These patients may be at higher risk for visual impairment and should be carefully examined for ophthalmological problems.  (+info)

Refractive errors in an urban population in Southern India: the Andhra Pradesh Eye Disease Study. (8/740)

PURPOSE: To assess the prevalence, distribution, and demographic associations of refractive error in an urban population in southern India. METHODS: Two thousand five hundred twenty-two subjects of all ages, representative of the Hyderabad population, were examined in the population-based Andhra Pradesh Eye Disease Study. Objective and subjective refraction was attempted on subjects >15 years of age with presenting distance and/or near visual acuity worse than 20/20 in either eye. Refraction under cycloplegia was attempted on all subjects < or =15 years of age. Spherical equivalent >0.50 D in the worse eye was considered as refractive error. Data on objective refraction under cycloplegia were analyzed for subjects < or =15 years and on subjective refraction were analyzed for subjects >15 years of age. RESULTS: Data on refractive error were available for 2,321 (92.0%) subjects. In subjects < or =15 years of age, age-gender-adjusted prevalence of myopia was 4.44% (95% confidence interval [CI], 2.14%-6.75%), which was higher in those 10 to 15 years of age (odds ratio, 2.75; 95% CI, 1.25-6.02), of hyperopia 59.37% (95% CI, 44.65%-74.09%), and of astigmatism 6.93% (95% CI, 4.90%-8.97%). In subjects >15 years of age, age-gender-adjusted prevalence of myopia was 19.39% (95% CI, 16.54%-22.24%), of hyperopia 9.83% (95% CI, 6.21%-13.45%), and of astigmatism 12.94% (95% CI, 10.80%-15.07%). With multivariate analysis, myopia was significantly higher in subjects with Lens Opacity Classification System HI nuclear cataract grade > or =3.5 (odds ratio, 9.10; 95% CI, 5.15-16.09), and in subjects with education of class 11 or higher (odds ratio, 1.80; 95% CI, 1.18-2.74); hyperopia was significantly higher in subjects > or =30 years of age compared with those 16 to 29 years of age (odds ratio, 37.26; 95% CI, 11.84-117.19), in females (odds ratio, 1.86; 95% CI, 1.33-2.61), and in subjects belonging to middle and upper socioeconomic strata (odds ratio, 2.10; 95% CI, 1.09-4.03); and astigmatism was significantly higher in subjects > or =40 years of age (odds ratio, 3.00; 95% CI, 2.23- 4.03) and in those with education of college level or higher (odds ratio, 1.73; 95% CI, 1.07-2.81). CONCLUSIONS: These population-based data on distribution and demographic associations of refractive error could enable planning of eye-care services to reduce visual impairment caused by refractive error. If these data are extrapolated to the 255 million urban population of India, among those >15 years of age an estimated 30 million people would have myopia, 15.2 million hyperopia, and 4.1 million astigmatism not concurrent with myopia or hyperopia; in addition, based on refraction under cycloplegia, 4.4 million children would have myopia and 2.5 million astigmatism not concurrent with myopia or hyperopia.  (+info)

Refractive errors are a group of vision conditions that include nearsightedness (myopia), farsightedness (hyperopia), astigmatism, and presbyopia. These conditions occur when the shape of the eye prevents light from focusing directly on the retina, causing blurred or distorted vision.

Myopia is a condition where distant objects appear blurry while close-up objects are clear. This occurs when the eye is too long or the cornea is too curved, causing light to focus in front of the retina instead of directly on it.

Hyperopia, on the other hand, is a condition where close-up objects appear blurry while distant objects are clear. This happens when the eye is too short or the cornea is not curved enough, causing light to focus behind the retina.

Astigmatism is a condition that causes blurred vision at all distances due to an irregularly shaped cornea or lens.

Presbyopia is a natural aging process that affects everyone as they get older, usually around the age of 40. It causes difficulty focusing on close-up objects and can be corrected with reading glasses, bifocals, or progressive lenses.

Refractive errors can be diagnosed through a comprehensive eye exam and are typically corrected with eyeglasses, contact lenses, or refractive surgery such as LASIK.

Myopia, also known as nearsightedness, is a common refractive error of the eye. It occurs when the eye is either too long or the cornea (the clear front part of the eye) is too curved. As a result, light rays focus in front of the retina instead of directly on it, causing distant objects to appear blurry while close objects remain clear.

Myopia typically develops during childhood and can progress gradually or rapidly until early adulthood. It can be corrected with glasses, contact lenses, or refractive surgery such as LASIK. Regular eye examinations are essential for people with myopia to monitor any changes in their prescription and ensure proper correction.

While myopia is generally not a serious condition, high levels of nearsightedness can increase the risk of certain eye diseases, including cataracts, glaucoma, retinal detachment, and myopic degeneration. Therefore, it's crucial to manage myopia effectively and maintain regular follow-ups with an eye care professional.

Hyperopia, also known as farsightedness, is a refractive error in which the eye does not focus light directly on the retina when looking at a distant object. Instead, light is focused behind the retina, causing close-up objects to appear blurry. This condition usually results from the eyeball being too short or the cornea having too little curvature. It can be corrected with eyeglasses, contact lenses, or refractive surgery.

Ocular refraction is a medical term that refers to the bending of light as it passes through the optical media of the eye, including the cornea and lens. This process allows the eye to focus light onto the retina, creating a clear image. The refractive power of the eye is determined by the curvature and transparency of these structures.

In a normal eye, light rays are bent or refracted in such a way that they converge at a single point on the retina, producing a sharp and focused image. However, if the curvature of the cornea or lens is too steep or too flat, the light rays may not converge properly, resulting in a refractive error such as myopia (nearsightedness), hyperopia (farsightedness), or astigmatism.

Ocular refraction can be measured using a variety of techniques, including retinoscopy, automated refraction, and subjective refraction. These measurements are used to determine the appropriate prescription for corrective lenses such as eyeglasses or contact lenses. In some cases, ocular refractive errors may be corrected surgically through procedures such as LASIK or PRK.

Eyeglasses are a medical device used to correct vision problems. Also known as spectacles, they consist of frames that hold one or more lenses through which a person looks to see clearly. The lenses may be made of glass or plastic and are designed to compensate for various visual impairments such as nearsightedness, farsightedness, astigmatism, or presbyopia. Eyeglasses can be custom-made to fit an individual's face and prescription, and they come in a variety of styles, colors, and materials. Some people wear eyeglasses all the time, while others may only need to wear them for certain activities such as reading or driving.

Retinoscopy is a diagnostic technique used in optometry and ophthalmology to estimate the refractive error of the eye, or in other words, to determine the prescription for eyeglasses or contact lenses. This procedure involves shining a light into the patient's pupil and observing the reflection off the retina while introducing different lenses in front of the patient's eye. The examiner then uses specific movements and observations to determine the amount and type of refractive error, such as myopia (nearsightedness), hyperopia (farsightedness), astigmatism, or presbyopia. Retinoscopy is a fundamental skill for eye care professionals and helps ensure that patients receive accurate prescriptions for corrective lenses.

Astigmatism is a common eye condition that occurs when the cornea or lens has an irregular shape, causing blurred or distorted vision. The cornea and lens are typically smooth and curved uniformly in all directions, allowing light to focus clearly on the retina. However, if the cornea or lens is not smoothly curved and has a steeper curve in one direction than the other, it causes light to focus unevenly on the retina, leading to astigmatism.

Astigmatism can cause blurred vision at all distances, as well as eye strain, headaches, and fatigue. It is often present from birth and can be hereditary, but it can also develop later in life due to eye injuries or surgery. Astigmatism can be corrected with glasses, contact lenses, or refractive surgery such as LASIK.

Ocular accommodation is the process by which the eye changes optical power to maintain a clear image or focus on an object as its distance varies. This is primarily achieved by the lens of the eye changing shape through the action of the ciliary muscles inside the eye. When you look at something far away, the lens becomes flatter, and when you look at something close up, the lens thickens. This ability to adjust focus allows for clear vision at different distances.

Vision screening is a quick and cost-effective method used to identify individuals who are at risk of vision problems or eye diseases. It is not a comprehensive eye examination, but rather an initial evaluation that helps to determine if a further, more in-depth examination by an eye care professional is needed. Vision screenings typically involve tests for visual acuity, distance and near vision, color perception, depth perception, and alignment of the eyes. The goal of vision screening is to detect potential vision issues early on, so that they can be treated promptly and effectively, thereby preventing or minimizing any negative impact on a person's overall vision and quality of life.

Visual acuity is a measure of the sharpness or clarity of vision. It is usually tested by reading an eye chart from a specific distance, such as 20 feet (6 meters). The standard eye chart used for this purpose is called the Snellen chart, which contains rows of letters that decrease in size as you read down the chart.

Visual acuity is typically expressed as a fraction, with the numerator representing the testing distance and the denominator indicating the smallest line of type that can be read clearly. For example, if a person can read the line on the eye chart that corresponds to a visual acuity of 20/20, it means they have normal vision at 20 feet. If their visual acuity is 20/40, it means they must be as close as 20 feet to see what someone with normal vision can see at 40 feet.

It's important to note that visual acuity is just one aspect of overall vision and does not necessarily reflect other important factors such as peripheral vision, depth perception, color vision, or contrast sensitivity.

Axial length, in the context of the eye, refers to the measurement of the distance between the front and back portions of the eye, specifically from the cornea (the clear front "window" of the eye) to the retina (the light-sensitive tissue at the back of the eye). This measurement is typically expressed in millimeters (mm).

The axial length of the eye is an important factor in determining the overall refractive power of the eye and can play a role in the development of various eye conditions, such as myopia (nearsightedness) or hyperopia (farsightedness). Changes in axial length, particularly elongation, are often associated with an increased risk of developing myopia. Regular monitoring of axial length can help eye care professionals track changes in the eye and manage these conditions more effectively.

Emmetropia is a term used in optometry and ophthalmology to describe a state where the eye's optical power is perfectly matched to the length of the eye. As a result, light rays entering the eye are focused directly on the retina, creating a clear image without the need for correction with glasses or contact lenses. It is the opposite of myopia (nearsightedness), hyperopia (farsightedness), or astigmatism, where the light rays are not properly focused on the retina, leading to blurry vision. Emmetropia is considered a normal and ideal eye condition.

Anisometropia is a medical term that refers to a condition where there is a significant difference in the refractive power between the two eyes. In other words, one eye has a significantly different optical prescription compared to the other eye. This condition can cause issues with binocular vision and depth perception, and can sometimes lead to amblyopia (lazy eye) if not corrected early in life. It is typically diagnosed through a comprehensive eye examination and can be corrected with glasses or contact lenses.

Biometry, also known as biometrics, is the scientific study of measurements and statistical analysis of living organisms. In a medical context, biometry is often used to refer to the measurement and analysis of physical characteristics or features of the human body, such as height, weight, blood pressure, heart rate, and other physiological variables. These measurements can be used for a variety of purposes, including diagnosis, treatment planning, monitoring disease progression, and research.

In addition to physical measurements, biometry may also refer to the use of statistical methods to analyze biological data, such as genetic information or medical images. This type of analysis can help researchers and clinicians identify patterns and trends in large datasets, and make predictions about health outcomes or treatment responses.

Overall, biometry is an important tool in modern medicine, as it allows healthcare professionals to make more informed decisions based on data and evidence.

The eye is the organ of sight, primarily responsible for detecting and focusing on visual stimuli. It is a complex structure composed of various parts that work together to enable vision. Here are some of the main components of the eye:

1. Cornea: The clear front part of the eye that refracts light entering the eye and protects the eye from harmful particles and microorganisms.
2. Iris: The colored part of the eye that controls the amount of light reaching the retina by adjusting the size of the pupil.
3. Pupil: The opening in the center of the iris that allows light to enter the eye.
4. Lens: A biconvex structure located behind the iris that further refracts light and focuses it onto the retina.
5. Retina: A layer of light-sensitive cells (rods and cones) at the back of the eye that convert light into electrical signals, which are then transmitted to the brain via the optic nerve.
6. Optic Nerve: The nerve that carries visual information from the retina to the brain.
7. Vitreous: A clear, gel-like substance that fills the space between the lens and the retina, providing structural support to the eye.
8. Conjunctiva: A thin, transparent membrane that covers the front of the eye and the inner surface of the eyelids.
9. Extraocular Muscles: Six muscles that control the movement of the eye, allowing for proper alignment and focus.

The eye is a remarkable organ that allows us to perceive and interact with our surroundings. Various medical specialties, such as ophthalmology and optometry, are dedicated to the diagnosis, treatment, and management of various eye conditions and diseases.

Mydriatics are medications that cause mydriasis, which is the dilation of the pupil. These drugs work by blocking the action of the muscarinic receptors in the iris, leading to relaxation of the circular muscle and constriction of the radial muscle, resulting in pupil dilation. Mydriatics are often used in eye examinations to facilitate examination of the interior structures of the eye. Commonly used mydriatic agents include tropicamide, phenylephrine, and cyclopentolate. It is important to note that mydriatics can have side effects such as blurred vision, photophobia, and accommodation difficulties, so patients should be advised accordingly.

Strabismus is a condition of the ocular muscles where the eyes are not aligned properly and point in different directions. One eye may turn inward, outward, upward, or downward while the other one remains fixed and aligns normally. This misalignment can occur occasionally or constantly. Strabismus is also commonly referred to as crossed eyes or walleye. The condition can lead to visual impairments such as amblyopia (lazy eye) and depth perception problems if not treated promptly and effectively, usually through surgery, glasses, or vision therapy.

Vision tests are a series of procedures used to assess various aspects of the visual system, including visual acuity, accommodation, convergence, divergence, stereopsis, color vision, and peripheral vision. These tests help healthcare professionals diagnose and manage vision disorders, such as nearsightedness, farsightedness, astigmatism, amblyopia, strabismus, and eye diseases like glaucoma, cataracts, and macular degeneration. Common vision tests include:

1. Visual acuity test (Snellen chart or letter chart): Measures the sharpness of a person's vision at different distances.
2. Refraction test: Determines the correct lens prescription for glasses or contact lenses by assessing how light is bent as it passes through the eye.
3. Color vision test: Evaluates the ability to distinguish between different colors and color combinations, often using pseudoisochromatic plates or Ishihara tests.
4. Stereopsis test: Assesses depth perception and binocular vision by presenting separate images to each eye that, when combined, create a three-dimensional effect.
5. Cover test: Examines eye alignment and the presence of strabismus (crossed eyes or turned eyes) by covering and uncovering each eye while observing eye movements.
6. Ocular motility test: Assesses the ability to move the eyes in various directions and coordinate both eyes during tracking and convergence/divergence movements.
7. Accommodation test: Evaluates the ability to focus on objects at different distances by using lenses, prisms, or dynamic retinoscopy.
8. Pupillary response test: Examines the size and reaction of the pupils to light and near objects.
9. Visual field test: Measures the peripheral (side) vision using automated perimetry or manual confrontation techniques.
10. Slit-lamp examination: Inspects the structures of the front part of the eye, such as the cornea, iris, lens, and anterior chamber, using a specialized microscope.

These tests are typically performed by optometrists, ophthalmologists, or other vision care professionals during routine eye examinations or when visual symptoms are present.

Amblyopia is a medical condition that affects the visual system, specifically the way the brain and eyes work together. It is often referred to as "lazy eye" and is characterized by reduced vision in one or both eyes that is not correctable with glasses or contact lenses alone. This occurs because the brain favors one eye over the other, causing the weaker eye to become neglected and underdeveloped.

Amblyopia can result from various conditions such as strabismus (eye misalignment), anisometropia (significant difference in prescription between the two eyes), or deprivation (such as a cataract that blocks light from entering the eye). Treatment for amblyopia typically involves correcting any underlying refractive errors, patching or blurring the stronger eye to force the weaker eye to work, and/or vision therapy. Early intervention is crucial to achieve optimal visual outcomes.

Cyclopentolate is a medication that belongs to a class of drugs called anticholinergics. It is primarily used as an eye drop to dilate the pupils and prevent the muscles in the eye from focusing, which can help doctors to examine the back of the eye more thoroughly.

The medical definition of Cyclopentolate is:

A cycloplegic and mydriatic agent that is used topically to produce pupillary dilation and cyclospasm, and to paralyze accommodation. It is used in the diagnosis and treatment of various ocular conditions, including refractive errors, corneal injuries, and uveitis. The drug works by blocking the action of acetylcholine, a neurotransmitter that is involved in the regulation of pupil size and focus.

Cyclopentolate is available as an eye drop solution, typically at concentrations of 0.5% or 1%. It is usually administered one to two times, with the second dose given after about 5 to 10 minutes. The effects of the drug can last for several hours, depending on the dosage and individual patient factors.

While cyclopentolate is generally considered safe when used as directed, it can cause side effects such as stinging or burning upon instillation, blurred vision, photophobia (sensitivity to light), and dry mouth. In rare cases, more serious side effects such as confusion, agitation, or hallucinations may occur, particularly in children or older adults. It is important to follow the instructions of a healthcare provider when using cyclopentolate, and to report any unusual symptoms or side effects promptly.

Medical definitions for visual impairment often vary, but according to the World Health Organization (WHO), visually impaired persons are those who have a best-corrected visual acuity of less than 0.3 (6/12) in their better eye or a visual field of less than 20 degrees in their better eye. This includes people who are blind, as well as those with partial sight.

Visual impairment can range from mild to severe and may result from a variety of causes, including genetic disorders, diseases, trauma, or aging. It is important to note that visual impairment does not necessarily mean total blindness; many visually impaired individuals have some remaining vision and can benefit from low vision services and assistive devices.

Low vision is a term used to describe significant visual impairment that cannot be corrected with standard glasses, contact lenses, medication or surgery. It is typically defined as visual acuity of less than 20/70 in the better-seeing eye after best correction, or a visual field of less than 20 degrees in the better-seeing eye.

People with low vision may have difficulty performing everyday tasks such as reading, recognizing faces, watching television, driving, or simply navigating their environment. They may also experience symptoms such as sensitivity to light, glare, or contrast, and may benefit from the use of visual aids, assistive devices, and rehabilitation services to help them maximize their remaining vision and maintain their independence.

Low vision can result from a variety of causes, including eye diseases such as macular degeneration, diabetic retinopathy, glaucoma, or cataracts, as well as congenital or inherited conditions, brain injuries, or aging. It is important for individuals with low vision to receive regular eye examinations and consult with a low vision specialist to determine the best course of treatment and management.

Optometry is a healthcare profession that involves examining, diagnosing, and treating disorders related to vision. Optometrists are the primary healthcare practitioners who specialize in prescribing and fitting eyeglasses and contact lenses to correct refractive errors such as myopia (nearsightedness), hyperopia (farsightedness), astigmatism, and presbyopia. They also diagnose and manage various eye diseases, including glaucoma, cataracts, and age-related macular degeneration. Optometrists may provide low vision care services to individuals with visual impairments and can offer pre- and post-operative care for patients undergoing eye surgery.

Optometry is a regulated profession that requires extensive education and training, including the completion of a Doctor of Optometry (O.D.) degree program and passing national and state licensing exams. In some jurisdictions, optometrists may also prescribe certain medications to treat eye conditions and diseases.

Presbyopia is a age-related eye condition, typically occurring after the age of 40, where the lens of the eye loses its flexibility and makes it difficult to focus on near objects. This results in blurred vision when reading, sewing or focusing on other close-up tasks. It's a natural part of the aging process and is not a disease. Corrective measures such as reading glasses, bifocals, multifocal lenses or contact lenses, or refractive surgery can help manage this condition.

Refractive surgical procedures are a type of ophthalmic surgery aimed at improving the refractive state of the eye and reducing or eliminating the need for corrective eyewear. These procedures reshape the cornea or alter the lens of the eye to correct nearsightedness (myopia), farsightedness (hyperopia), presbyopia, or astigmatism.

Examples of refractive surgical procedures include:

1. Laser-assisted in situ keratomileusis (LASIK): A laser is used to create a thin flap in the cornea, which is then lifted to allow reshaping of the underlying tissue with another laser. The flap is replaced, and the procedure is completed.
2. Photorefractive keratectomy (PRK): This procedure involves removing the outer layer of the cornea (epithelium) and using a laser to reshape the underlying tissue. A bandage contact lens is placed over the eye to protect it during healing.
3. LASEK (laser-assisted subepithelial keratomileusis): Similar to LASIK, but instead of creating a flap, the epithelium is loosened with an alcohol solution and moved aside. The laser treatment is applied, and the epithelium is replaced.
4. Small Incision Lenticule Extraction (SMILE): A femtosecond laser creates a small lenticule within the cornea, which is then removed through a tiny incision. This procedure reshapes the cornea to correct refractive errors.
5. Refractive lens exchange (RLE): The eye's natural lens is removed and replaced with an artificial intraocular lens (IOL) to correct refractive errors, similar to cataract surgery.
6. Implantable contact lenses: A thin, foldable lens is placed between the iris and the natural lens or behind the iris to improve the eye's focusing power.

These procedures are typically performed on an outpatient basis and may require topical anesthesia (eye drops) or local anesthesia. Potential risks and complications include infection, dry eye, visual disturbances, and changes in night vision. It is essential to discuss these potential risks with your ophthalmologist before deciding on a refractive surgery procedure.

Vision disorders refer to a wide range of conditions that affect the visual system and result in various symptoms, such as blurry vision, double vision, distorted vision, impaired depth perception, and difficulty with visual tracking or focusing. These disorders can be categorized into several types, including:

1. Refractive errors: These occur when the shape of the eye prevents light from focusing directly on the retina, resulting in blurry vision. Examples include myopia (nearsightedness), hyperopia (farsightedness), astigmatism, and presbyopia (age-related loss of near vision).
2. Strabismus: Also known as crossed eyes or walleye, strabismus is a misalignment of the eyes where they point in different directions, which can lead to double vision or loss of depth perception.
3. Amblyopia: Often called lazy eye, amblyopia is a condition where one eye has reduced vision due to lack of proper visual development during childhood. It may be caused by strabismus, refractive errors, or other factors that interfere with normal visual development.
4. Accommodative disorders: These involve problems with the focusing ability of the eyes, such as convergence insufficiency (difficulty focusing on close objects) and accommodative dysfunction (inability to maintain clear vision at different distances).
5. Binocular vision disorders: These affect how the eyes work together as a team, leading to issues like poor depth perception, eye strain, and headaches. Examples include convergence insufficiency, divergence excess, and suppression.
6. Ocular motility disorders: These involve problems with eye movement, such as nystagmus (involuntary eye movements), strabismus, or restricted extraocular muscle function.
7. Visual processing disorders: These affect the brain's ability to interpret and make sense of visual information, even when the eyes themselves are healthy. Symptoms may include difficulty with reading, recognizing shapes and objects, and understanding spatial relationships.
8. Low vision: This term refers to significant visual impairment that cannot be fully corrected with glasses, contact lenses, medication, or surgery. It includes conditions like macular degeneration, diabetic retinopathy, glaucoma, and cataracts.
9. Blindness: Complete loss of sight in both eyes, which can be caused by various factors such as injury, disease, or genetic conditions.

Eye diseases are a range of conditions that affect the eye or visual system, causing damage to vision and, in some cases, leading to blindness. These diseases can be categorized into various types, including:

1. Refractive errors: These include myopia (nearsightedness), hyperopia (farsightedness), astigmatism, and presbyopia, which affect the way light is focused on the retina and can usually be corrected with glasses or contact lenses.
2. Cataracts: A clouding of the lens inside the eye that leads to blurry vision, glare, and decreased contrast sensitivity. Cataract surgery is the most common treatment for this condition.
3. Glaucoma: A group of diseases characterized by increased pressure in the eye, leading to damage to the optic nerve and potential blindness if left untreated. Treatment includes medications, laser therapy, or surgery.
4. Age-related macular degeneration (AMD): A progressive condition that affects the central part of the retina called the macula, causing blurry vision and, in advanced stages, loss of central vision. Treatment may include anti-VEGF injections, laser therapy, or nutritional supplements.
5. Diabetic retinopathy: A complication of diabetes that affects the blood vessels in the retina, leading to bleeding, leakage, and potential blindness if left untreated. Treatment includes laser therapy, anti-VEGF injections, or surgery.
6. Retinal detachment: A separation of the retina from its underlying tissue, which can lead to vision loss if not treated promptly with surgery.
7. Amblyopia (lazy eye): A condition where one eye does not develop normal vision, often due to a misalignment or refractive error in childhood. Treatment includes correcting the underlying problem and encouraging the use of the weaker eye through patching or other methods.
8. Strabismus (crossed eyes): A misalignment of the eyes that can lead to amblyopia if not treated promptly with surgery, glasses, or other methods.
9. Corneal diseases: Conditions that affect the transparent outer layer of the eye, such as keratoconus, Fuchs' dystrophy, and infectious keratitis, which can lead to vision loss if not treated promptly.
10. Uveitis: Inflammation of the middle layer of the eye, which can cause vision loss if not treated promptly with anti-inflammatory medications or surgery.

Corneal topography is a non-invasive medical imaging technique used to create a detailed map of the surface curvature of the cornea, which is the clear, dome-shaped surface at the front of the eye. This procedure provides valuable information about the shape and condition of the cornea, helping eye care professionals assess various eye conditions such as astigmatism, keratoconus, and other corneal abnormalities. It can also be used in contact lens fitting, refractive surgery planning, and post-surgical evaluation.

Sensory deprivation, also known as perceptual isolation or sensory restriction, refers to the deliberate reduction or removal of stimuli from one or more of the senses. This can include limiting input from sight, sound, touch, taste, and smell. The goal is to limit a person's sensory experiences in order to study the effects on cognition, perception, and behavior.

In a clinical context, sensory deprivation can occur as a result of certain medical conditions or treatments, such as blindness, deafness, or pharmacological interventions that affect sensory processing. Prolonged sensory deprivation can lead to significant psychological and physiological effects, including hallucinations, delusions, and decreased cognitive function.

It's important to note that sensory deprivation should not be confused with meditation or relaxation techniques that involve reducing external stimuli in a controlled manner to promote relaxation and focus.

A pupil, in medical terms, refers to the circular opening in the center of the iris (the colored part of the eye) that allows light to enter and reach the retina. The size of the pupil can change involuntarily in response to light intensity and emotional state, as well as voluntarily through certain eye exercises or with the use of eye drops. Pupillary reactions are important in clinical examinations as they can provide valuable information about the nervous system's functioning, particularly the brainstem and cranial nerves II and III.

I'm sorry for any confusion, but "Singapore" is not a medical term or concept. It is a sovereign city-state and island country in Southeast Asia. If you have any questions related to medical topics or definitions, I would be happy to try and help answer those for you!

Esotropia is a type of ocular misalignment, also known as strabismus, in which one eye turns inward toward the nose. This condition can be constant or intermittent and may result in double vision or loss of depth perception. Esotropia is often classified based on its cause, age of onset, and frequency. Common forms include congenital esotropia, acquired esotropia, and accommodative esotropia. Treatment typically involves corrective eyewear, eye exercises, or surgery to realign the eyes.

The anterior chamber is the front portion of the eye, located between the cornea (the clear front "window" of the eye) and the iris (the colored part of the eye). It is filled with a clear fluid called aqueous humor that provides nutrients to the structures inside the eye and helps maintain its shape. The anterior chamber plays an important role in maintaining the overall health and function of the eye.

In the context of medical terminology, "lenses" generally refers to optical lenses used in various medical devices and instruments. These lenses are typically made of glass or plastic and are designed to refract (bend) light in specific ways to help magnify, focus, or redirect images. Here are some examples:

1. In ophthalmology and optometry, lenses are used in eyeglasses, contact lenses, and ophthalmic instruments to correct vision problems like myopia (nearsightedness), hypermetropia (farsightedness), astigmatism, or presbyopia.
2. In surgical microscopes, lenses are used to provide a magnified and clear view of the operating field during microsurgical procedures like ophthalmic, neurosurgical, or ENT (Ear, Nose, Throat) surgeries.
3. In endoscopes and laparoscopes, lenses are used to transmit light and images from inside the body during minimally invasive surgical procedures.
4. In ophthalmic diagnostic instruments like slit lamps, lenses are used to examine various structures of the eye in detail.

In summary, "lenses" in medical terminology refer to optical components that help manipulate light to aid in diagnosis, treatment, or visual correction.

Blindness is a condition of complete or near-complete vision loss. It can be caused by various factors such as eye diseases, injuries, or birth defects. Total blindness means that a person cannot see anything at all, while near-complete blindness refers to having only light perception or the ability to perceive the direction of light, but not able to discern shapes or forms. Legal blindness is a term used to define a certain level of visual impairment that qualifies an individual for government assistance and benefits; it usually means best corrected visual acuity of 20/200 or worse in the better eye, or a visual field no greater than 20 degrees in diameter.

Contact lenses are thin, curved plastic or silicone hydrogel devices that are placed on the eye to correct vision, replace a missing or damaged cornea, or for cosmetic purposes. They rest on the surface of the eye, called the cornea, and conform to its shape. Contact lenses are designed to float on a thin layer of tears and move with each blink.

There are two main types of contact lenses: soft and rigid gas permeable (RGP). Soft contact lenses are made of flexible hydrophilic (water-absorbing) materials that allow oxygen to pass through the lens to the cornea. RGP lenses are made of harder, more oxygen-permeable materials.

Contact lenses can be used to correct various vision problems, including nearsightedness, farsightedness, astigmatism, and presbyopia. They come in different shapes, sizes, and powers to suit individual needs and preferences. Proper care, handling, and regular check-ups with an eye care professional are essential for maintaining good eye health and preventing complications associated with contact lens wear.

The cornea is the clear, dome-shaped surface at the front of the eye. It plays a crucial role in focusing vision. The cornea protects the eye from harmful particles and microorganisms, and it also serves as a barrier against UV light. Its transparency allows light to pass through and get focused onto the retina. The cornea does not contain blood vessels, so it relies on tears and the fluid inside the eye (aqueous humor) for nutrition and oxygen. Any damage or disease that affects its clarity and shape can significantly impact vision and potentially lead to blindness if left untreated.

Prevalence, in medical terms, refers to the total number of people in a given population who have a particular disease or condition at a specific point in time, or over a specified period. It is typically expressed as a percentage or a ratio of the number of cases to the size of the population. Prevalence differs from incidence, which measures the number of new cases that develop during a certain period.

Aberrometry is a medical diagnostic technique used to measure the amount and type of aberration or distortion in the optical system of the eye. It is often used to evaluate the quality of vision, particularly in cases where traditional methods of measuring visual acuity are not sufficient.

During an aberrometry test, the patient looks into a specialized instrument called a wavefront sensor while a series of light patterns are projected onto the retina. The sensor then measures how the light is distorted as it passes through the eye's optical system, including the cornea and lens. This information is used to create a detailed map of the eye's aberrations, which can help doctors identify any irregularities that may be contributing to visual symptoms such as blurred vision, glare, or halos around lights.

Aberrometry is often used in conjunction with other diagnostic tests to evaluate patients who are considering refractive surgery, such as LASIK or PRK. By identifying any abnormalities in the eye's optical system, doctors can determine whether a patient is a good candidate for surgery and make more informed decisions about how to proceed with treatment.

A cataract is a clouding of the natural lens in the eye that affects vision. This clouding can cause vision to become blurry, faded, or dim, making it difficult to see clearly. Cataracts are a common age-related condition, but they can also be caused by injury, disease, or medication use. In most cases, cataracts develop gradually over time and can be treated with surgery to remove the cloudy lens and replace it with an artificial one.

Degenerative Myopia is a progressive form of nearsightedness, characterized by excessive elongation of the eyeball, which results in a steep curvature of the cornea and an overly long axial length. This condition causes light to focus in front of the retina instead of directly on it, resulting in blurred distance vision.

In degenerative myopia, this elongation continues throughout adulthood and is often associated with various complications such as thinning of the retinal tissue, stretching of the layers beneath the retina, and abnormal blood vessel growth. These changes can lead to a higher risk of developing retinal detachment, macular holes, glaucoma, and cataracts.

Degenerative myopia is considered a more severe form of myopia than the common or simple myopia, which usually stabilizes in the teenage years. It is also sometimes referred to as pathological myopia or malignant myopia. Regular eye examinations are essential for individuals with degenerative myopia to monitor and manage any potential complications.

Laser In Situ Keratomileusis (LASIK) is a type of refractive surgery used to correct vision issues such as myopia (nearsightedness), hyperopia (farsightedness), and astigmatism. The procedure involves reshaping the cornea, which is the clear, dome-shaped surface at the front of the eye, using an excimer laser.

In LASIK, a thin flap is created on the surface of the cornea using a femtosecond or microkeratome laser. The flap is then lifted, and the excimer laser is used to reshape the underlying tissue. After the reshaping is complete, the flap is replaced, allowing for quicker healing and visual recovery compared to other refractive surgery procedures.

LASIK is an outpatient procedure that typically takes about 30 minutes or less per eye. Most people can expect to see improved vision within a few days of the procedure, although it may take several weeks for vision to fully stabilize. LASIK has a high success rate and is generally considered safe when performed by a qualified surgeon. However, as with any surgical procedure, there are risks involved, including dry eye, infection, and visual complications such as glare or halos around lights.

Radial Keratotomy (RK) is a type of refractive surgery used to correct vision problems such as nearsightedness and astigmatism. The procedure involves making small, precise incisions in the cornea in a radial pattern, like the spokes of a wheel. These incisions cause the cornea to change shape, which can help to improve the way that light is focused onto the retina and reduce the need for corrective lenses.

During the procedure, the surgeon uses a specialized blade or laser to make the incisions in the cornea. The incisions are typically made at the periphery of the cornea, leaving the central portion of the cornea untouched. This helps to preserve the strength and stability of the cornea while still allowing it to change shape enough to improve vision.

Radial keratotomy was first developed in the 1970s and was widely used in the 1980s and 1990s. However, it has largely been replaced by newer procedures such as LASIK and PRK, which are considered to be safer and more effective. RK is still occasionally performed in cases where other procedures are not an option or when a patient prefers this type of surgery.

It's important to note that any surgical procedure carries risks, including infection, scarring, and changes in vision. Patients considering radial keratotomy should discuss the potential benefits and risks with their eye care provider before making a decision.

The crystalline lens is a biconvex transparent structure in the eye that helps to refract (bend) light rays and focus them onto the retina. It is located behind the iris and pupil and is suspended by small fibers called zonules that connect it to the ciliary body. The lens can change its shape to accommodate and focus on objects at different distances, a process known as accommodation. With age, the lens may become cloudy or opaque, leading to cataracts.

Interferometry is not specifically a medical term, but it is used in certain medical fields such as ophthalmology and optics research. Here is a general definition:

Interferometry is a physical method that uses the interference of waves to measure the differences in phase between two or more waves. In other words, it's a technique that combines two or more light waves to create an interference pattern, which can then be analyzed to extract information about the properties of the light waves, such as their wavelength, amplitude, and phase.

In ophthalmology, interferometry is used in devices like wavefront sensors to measure the aberrations in the eye's optical system. By analyzing the interference pattern created by the light passing through the eye, these devices can provide detailed information about the shape and curvature of the cornea and lens, helping doctors to diagnose and treat various vision disorders.

In optics research, interferometry is used to study the properties of light waves and materials that interact with them. By analyzing the interference patterns created by light passing through different materials or devices, researchers can gain insights into their optical properties, such as their refractive index, thickness, and surface roughness.

Photorefractive Keratectomy (PRK) is a type of refractive surgery used to correct vision issues such as nearsightedness, farsightedness, and astigmatism. It works by reshaping the cornea using a laser, which alters how light enters the eye and focuses on the retina.

In PRK, the surgeon removes the thin outer layer of the cornea (epithelium) with an alcohol solution or a blunt surgical instrument before using the laser to reshape the underlying stromal layer. The epithelium then grows back during the healing process, which can take several days.

Compared to LASIK (another type of refractive surgery), PRK has a longer recovery time and may cause more discomfort in the first few days after surgery. However, it is an option for people who are not good candidates for LASIK due to thin corneas or other eye conditions.

It's important to note that while refractive surgeries like PRK can significantly improve vision and reduce dependence on glasses or contact lenses, they may not completely eliminate the need for corrective eyewear in all cases. Additionally, as with any surgical procedure, there are potential risks and complications associated with PRK, including infection, dry eye, and visual disturbances such as glare or halos around lights.

East Timor, also known as Timor-Leste, is a country located in Southeast Asia and Oceania. It is situated on the eastern half of the island of Timor, with the western half being part of Indonesia. East Timor became an independent nation in 2002 after a long period of colonization by Portugal and a violent struggle for independence from Indonesia. The country has faced significant challenges in its development, including poverty, unemployment, and lack of infrastructure.

In medical terms, there may not be specific definitions related solely to East Timor. However, like any other country, health issues and concerns can arise within the population that would be relevant to discuss in a medical context. These could include infectious diseases prevalent in the region, nutritional deficiencies, maternal and child health, access to healthcare services, and environmental health factors, among others.

An excimer laser is a type of laser that is used in various medical procedures, particularly in ophthalmology and dermatology. The term "excimer" is derived from "excited dimer," which refers to a short-lived molecule formed when two atoms combine in an excited state.

Excimer lasers emit light at a specific wavelength that is determined by the type of gas used in the laser. In medical applications, excimer lasers typically use noble gases such as argon, krypton, or xenon, combined with halogens such as fluorine or chlorine. The most commonly used excimer laser in medical procedures is the excimer laser that uses a mixture of argon and fluoride gas to produce light at a wavelength of 193 nanometers (nm).

In ophthalmology, excimer lasers are primarily used for refractive surgery, such as LASIK and PRK, to correct vision problems like myopia, hyperopia, and astigmatism. The laser works by vaporizing tiny amounts of tissue from the cornea, reshaping its curvature to improve the way light is focused onto the retina.

In dermatology, excimer lasers are used for various skin conditions, including psoriasis, vitiligo, and atopic dermatitis. The laser works by emitting high-energy ultraviolet (UV) light that selectively targets and destroys the abnormal cells responsible for these conditions while leaving surrounding healthy tissue intact.

Excimer lasers are known for their precision, accuracy, and minimal side effects, making them a popular choice in medical procedures where fine detail and tissue preservation are critical.

Intraocular lens (IOL) implantation is a surgical procedure that involves placing a small artificial lens inside the eye to replace the natural lens that has been removed. This procedure is typically performed during cataract surgery, where the cloudy natural lens is removed and replaced with an IOL to restore clear vision.

During the procedure, a small incision is made in the eye, and the cloudy lens is broken up and removed using ultrasound waves or laser energy. Then, the folded IOL is inserted through the same incision and positioned in the correct place inside the eye. Once in place, the IOL unfolds and is secured into position.

There are several types of IOLs available, including monofocal, multifocal, toric, and accommodating lenses. Monofocal lenses provide clear vision at one distance, while multifocal lenses offer clear vision at multiple distances. Toric lenses correct astigmatism, and accommodating lenses can change shape to focus on objects at different distances.

Overall, intraocular lens implantation is a safe and effective procedure that can help restore clear vision in patients with cataracts or other eye conditions that require the removal of the natural lens.

"Age distribution" is a term used to describe the number of individuals within a population or sample that fall into different age categories. It is often presented in the form of a graph, table, or chart, and can provide important information about the demographic structure of a population.

The age distribution of a population can be influenced by a variety of factors, including birth rates, mortality rates, migration patterns, and aging. Public health officials and researchers use age distribution data to inform policies and programs related to healthcare, social services, and other areas that affect the well-being of populations.

For example, an age distribution graph might show a larger number of individuals in the younger age categories, indicating a population with a high birth rate. Alternatively, it might show a larger number of individuals in the older age categories, indicating a population with a high life expectancy or an aging population. Understanding the age distribution of a population can help policymakers plan for future needs and allocate resources more effectively.

Exotropia is a type of ocular misalignment or strabismus, where one eye turns outward (towards the ear) while the other eye remains aligned straight ahead. This condition can be constant or intermittent and may result in limited or absent depth perception, double vision, and in some cases, amblyopia (lazy eye). Exotropia is typically diagnosed during childhood through a comprehensive eye examination by an optometrist or ophthalmologist. Treatment options include eyeglasses, prism lenses, vision therapy, or surgery, depending on the severity and frequency of the misalignment.

The vitreous body, also known simply as the vitreous, is the clear, gel-like substance that fills the space between the lens and the retina in the eye. It is composed mainly of water, but also contains collagen fibers, hyaluronic acid, and other proteins. The vitreous helps to maintain the shape of the eye and provides a transparent medium for light to pass through to reach the retina. With age, the vitreous can become more liquefied and may eventually separate from the retina, leading to symptoms such as floaters or flashes of light.

I apologize for any confusion, but "Belize" is not a medical term or concept. It is the name of a country located in Central America, bordered by Mexico to the north, Guatemala to the west and south, and the Caribbean Sea to the east. If you have any questions related to medical terminology or health-related topics, I would be happy to help with those instead.

The term "Asian Continental Ancestry Group" is a medical/ethnic classification used to describe a person's genetic background and ancestry. According to this categorization, individuals with origins in the Asian continent are grouped together. This includes populations from regions such as East Asia (e.g., China, Japan, Korea), South Asia (e.g., India, Pakistan, Bangladesh), Southeast Asia (e.g., Philippines, Indonesia, Thailand), and Central Asia (e.g., Kazakhstan, Uzbekistan, Tajikistan). It is important to note that this broad categorization may not fully capture the genetic diversity within these regions or accurately reflect an individual's specific ancestral origins.

"Sex distribution" is a term used to describe the number of males and females in a study population or sample. It can be presented as a simple count, a percentage, or a ratio. This information is often used in research to identify any differences in health outcomes, disease prevalence, or response to treatment between males and females. Additionally, understanding sex distribution can help researchers ensure that their studies are representative of the general population and can inform the design of future studies.

Diagnostic errors refer to inaccurate or delayed diagnoses of a patient's medical condition, which can lead to improper or unnecessary treatment and potentially serious harm to the patient. These errors can occur due to various factors such as lack of clinical knowledge, failure to consider all possible diagnoses, inadequate communication between healthcare providers and patients, and problems with testing or interpretation of test results. Diagnostic errors are a significant cause of preventable harm in medical care and have been identified as a priority area for quality improvement efforts.

Ocular albinism is a type of albinism that primarily affects the eyes. It is a genetic disorder characterized by the reduction or absence of melanin, the pigment responsible for coloring the skin, hair, and eyes. In ocular albinism, melanin production is deficient in the eyes, leading to various eye abnormalities.

The main features of ocular albinism include:

1. Nystagmus: Rapid, involuntary back-and-forth movement of the eyes.
2. Iris transillumination: The iris appears translucent due to the lack of pigment, allowing light to pass through easily. This can be observed using a light source shone into the eye.
3. Foveal hypoplasia: Underdevelopment or absence of the fovea, a small pit in the retina responsible for sharp, central vision.
4. Photophobia: Increased sensitivity to light due to the lack of pigment in the eyes.
5. Strabismus: Misalignment of the eyes, which can result in double vision or lazy eye.
6. Reduced visual acuity: Decreased ability to see clearly, even with corrective lenses.

Ocular albinism is typically inherited as an X-linked recessive trait, meaning it primarily affects males, while females can be carriers of the condition. However, there are also autosomal recessive forms of ocular albinism that can affect both males and females equally. Treatment for ocular albinism usually involves managing symptoms with corrective lenses, low-vision aids, and vision therapy to improve visual skills.

Diagnostic techniques in ophthalmology refer to the various methods and tests used by eye specialists (ophthalmologists) to examine, evaluate, and diagnose conditions related to the eyes and visual system. Here are some commonly used diagnostic techniques:

1. Visual Acuity Testing: This is a basic test to measure the sharpness of a person's vision. It typically involves reading letters or numbers from an eye chart at a specific distance.
2. Refraction Test: This test helps determine the correct lens prescription for glasses or contact lenses by measuring how light is bent as it passes through the cornea and lens.
3. Slit Lamp Examination: A slit lamp is a microscope that allows an ophthalmologist to examine the structures of the eye, including the cornea, iris, lens, and retina, in great detail.
4. Tonometry: This test measures the pressure inside the eye (intraocular pressure) to detect conditions like glaucoma. Common methods include applanation tonometry and non-contact tonometry.
5. Retinal Imaging: Several techniques are used to capture images of the retina, including fundus photography, fluorescein angiography, and optical coherence tomography (OCT). These tests help diagnose conditions like macular degeneration, diabetic retinopathy, and retinal detachments.
6. Color Vision Testing: This test evaluates a person's ability to distinguish between different colors, which can help detect color vision deficiencies or neurological disorders affecting the visual pathway.
7. Visual Field Testing: This test measures a person's peripheral (or side) vision and can help diagnose conditions like glaucoma, optic nerve damage, or brain injuries.
8. Pupillary Reactions Tests: These tests evaluate how the pupils respond to light and near objects, which can provide information about the condition of the eye's internal structures and the nervous system.
9. Ocular Motility Testing: This test assesses eye movements and alignment, helping diagnose conditions like strabismus (crossed eyes) or nystagmus (involuntary eye movement).
10. Corneal Topography: This non-invasive imaging technique maps the curvature of the cornea, which can help detect irregularities, assess the fit of contact lenses, and plan refractive surgery procedures.

Tropicamide is a muscarinic antagonist, which is a type of drug that blocks the action of acetylcholine in the body. In particular, it blocks the muscarinic receptors found in the eye, which results in pupil dilation (mydriasis) and paralysis of the ciliary muscle (cycloplegia).

Tropicamide is commonly used in ophthalmology as a diagnostic aid during eye examinations. It is often instilled into the eye to dilate the pupil, which allows the eye care professional to more easily examine the back of the eye and assess conditions such as cataracts, glaucoma, or retinal disorders. The cycloplegic effect of tropicamide also helps to relax the accommodation reflex, making it easier to measure the refractive error of the eye and determine the appropriate prescription for eyeglasses or contact lenses.

It is important to note that tropicamide can cause temporary blurring of vision and sensitivity to light, so patients should be advised not to drive or operate heavy machinery until the effects of the medication have worn off.

Ocular vision refers to the ability to process and interpret visual information that is received by the eyes. This includes the ability to see clearly and make sense of the shapes, colors, and movements of objects in the environment. The ocular system, which includes the eye and related structures such as the optic nerve and visual cortex of the brain, works together to enable vision.

There are several components of ocular vision, including:

* Visual acuity: the clarity or sharpness of vision
* Field of vision: the extent of the visual world that is visible at any given moment
* Color vision: the ability to distinguish different colors
* Depth perception: the ability to judge the distance of objects in three-dimensional space
* Contrast sensitivity: the ability to distinguish an object from its background based on differences in contrast

Disorders of ocular vision can include refractive errors such as nearsightedness or farsightedness, as well as more serious conditions such as cataracts, glaucoma, and macular degeneration. These conditions can affect one or more aspects of ocular vision and may require medical treatment to prevent further vision loss.

I'm sorry for any confusion, but "Optics and Photonics" is a broad field that encompasses various scientific and engineering disciplines. It doesn't have a specific medical definition, as it's not a term typically used in a medical context.

However, I can provide a general definition:

Optics is the study of light and its interactions with matter. This includes how light is produced, controlled, transmitted, and detected. It involves phenomena such as reflection, refraction, diffraction, and interference.

Photonics, on the other hand, is a branch of optics that deals with the generation, detection, and manipulation of individual photons, the basic units of light. Photonics is often applied to technologies such as lasers, fiber optics, and optical communications.

In a medical context, these fields might be used in various diagnostic and therapeutic applications, such as endoscopes, ophthalmic devices, laser surgery, and imaging technologies like MRI and CT scans. But the terms "Optics" and "Photonics" themselves are not medical conditions or treatments.

A cross-sectional study is a type of observational research design that examines the relationship between variables at one point in time. It provides a snapshot or a "cross-section" of the population at a particular moment, allowing researchers to estimate the prevalence of a disease or condition and identify potential risk factors or associations.

In a cross-sectional study, data is collected from a sample of participants at a single time point, and the variables of interest are measured simultaneously. This design can be used to investigate the association between exposure and outcome, but it cannot establish causality because it does not follow changes over time.

Cross-sectional studies can be conducted using various data collection methods, such as surveys, interviews, or medical examinations. They are often used in epidemiology to estimate the prevalence of a disease or condition in a population and to identify potential risk factors that may contribute to its development. However, because cross-sectional studies only provide a snapshot of the population at one point in time, they cannot account for changes over time or determine whether exposure preceded the outcome.

Therefore, while cross-sectional studies can be useful for generating hypotheses and identifying potential associations between variables, further research using other study designs, such as cohort or case-control studies, is necessary to establish causality and confirm any findings.

The choroid is a layer of the eye that contains blood vessels that supply oxygen and nutrients to the outer layers of the retina. It lies between the sclera (the white, protective coat of the eye) and the retina (the light-sensitive tissue at the back of the eye). The choroid is essential for maintaining the health and function of the retina, particularly the photoreceptor cells that detect light and transmit visual signals to the brain. Damage to the choroid can lead to vision loss or impairment.

I'm sorry for any confusion, but "India" is not a medical term or concept. It is a country in South Asia, the second-most populous country in the world, known for its rich history, diverse culture, and numerous contributions to various fields including medicine. If you have any questions related to medical topics, I would be happy to help answer them!

Hydrophilic contact lenses are a type of contact lens that is designed to absorb and retain water. These lenses are made from materials that have an affinity for water, which helps them to remain moist and comfortable on the eye. The water content of hydrophilic contact lenses can vary, but typically ranges from 30-80% by weight.

Hydrophilic contact lenses are often used to correct refractive errors such as myopia (nearsightedness), hyperopia (farsightedness), and astigmatism. They can be made in a variety of materials, including soft hydrogel and silicone hydrogel.

One advantage of hydrophilic contact lenses is that they tend to be more comfortable to wear than other types of contacts, as they retain moisture and conform closely to the shape of the eye. However, they may also be more prone to deposits and buildup, which can lead to protein accumulation and discomfort over time. Proper care and cleaning are essential to maintain the health of the eyes when wearing hydrophilic contact lenses.

Optical coherence tomography (OCT) is a non-invasive imaging technique that uses low-coherence light to capture high-resolution cross-sectional images of biological tissues, particularly the retina and other ocular structures. OCT works by measuring the echo time delay of light scattered back from different depths within the tissue, creating a detailed map of the tissue's structure. This technique is widely used in ophthalmology to diagnose and monitor various eye conditions such as macular degeneration, diabetic retinopathy, and glaucoma.

I'm sorry for any confusion, but "photography" is not a term typically used in medical definitions. Photography refers to the art, application, or process of creating images by recording light or other electromagnetic radiation, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film.

If you're looking for a medical term related to imaging, there are several terms that might be relevant, such as:

1. Radiography: This is a technique using X-rays to visualize the internal structures of the body.
2. Ultrasonography: Also known as ultrasound, this is a diagnostic imaging technique using high-frequency sound waves to create images of the inside of the body.
3. Computed Tomography (CT): A type of imaging that uses X-rays to create detailed cross-sectional images of the body.
4. Magnetic Resonance Imaging (MRI): A type of imaging that uses magnetic fields and radio waves to create detailed images of the organs and tissues within the body.
5. Nuclear Medicine: This is a branch of medical imaging that uses small amounts of radioactive material to diagnose and treat diseases.

If you have any questions related to medical definitions or topics, feel free to ask!

Refractometry is a medical laboratory technique used to measure the refractive index of a substance, typically a liquid. The refractive index is the ratio of the speed of light in a vacuum to its speed in the substance being measured. In a clinical setting, refractometry is often used to determine the concentration of total solids in a fluid, such as urine or serum, by measuring the angle at which light passes through the sample. This information can be useful in the diagnosis and monitoring of various medical conditions, including dehydration, kidney disease, and diabetes. Refractometry is also used in the field of optometry to measure the refractive error of the eye, or the amount and type of correction needed to provide clear vision.

Ophthalmology is a branch of medicine that deals with the diagnosis, treatment, and prevention of diseases and disorders of the eye and visual system. It is a surgical specialty, and ophthalmologists are medical doctors who complete additional years of training to become experts in eye care. They are qualified to perform eye exams, diagnose and treat eye diseases, prescribe glasses and contact lenses, and perform eye surgery. Some subspecialties within ophthalmology include cornea and external disease, glaucoma, neuro-ophthalmology, pediatric ophthalmology, retina and vitreous, and oculoplastics.

Retinopathy of Prematurity (ROP) is a potentially sight-threatening proliferative retinal vascular disorder that primarily affects prematurely born infants, particularly those with low birth weight and/or young gestational age. It is characterized by the abnormal growth and development of retinal blood vessels due to disturbances in the oxygen supply and metabolic demands during critical phases of fetal development.

The condition can be classified into various stages (1-5) based on its severity, with stages 4 and 5 being more severe forms that may lead to retinal detachment and blindness if left untreated. The pathogenesis of ROP involves an initial phase of vessel loss and regression in the central retina, followed by a secondary phase of abnormal neovascularization, which can cause fibrosis, traction, and ultimately, retinal detachment.

ROP is typically managed with a multidisciplinary approach involving ophthalmologists, neonatologists, and pediatricians. Treatment options include laser photocoagulation, cryotherapy, intravitreal anti-VEGF injections, or even surgical interventions to prevent retinal detachment and preserve vision. Regular screening examinations are crucial for early detection and timely management of ROP in at-risk infants.

Ocular convergence is the normal, inward movement of both eyes towards each other to focus on a nearby object. This coordinated action allows for single, clear vision (binocular vision) of the object. It is an important component of visual function and is controlled by the brain receiving input from the muscles that move the eyes.

Convergence insufficiency is a common condition where the eyes have difficulty maintaining alignment during close work, such as reading or using a computer. This can result in eye strain, double vision, and difficulty concentrating. Treatment for convergence insufficiency may include vision therapy, exercises to improve convergence ability, and/or the use of prism lenses.

Diplopia is a medical term that refers to the condition where a person sees two images of a single object. It is commonly known as double vision. This can occur due to various reasons, such as nerve damage or misalignment of the eyes. Diplopia can be temporary or chronic and can affect one or both eyes. If you're experiencing diplopia, it's essential to consult an eye care professional for proper evaluation and treatment.

Monocular vision refers to the ability to see and process visual information using only one eye. It is the type of vision that an individual has when they are using only one eye to look at something, while the other eye may be covered or not functioning. This can be contrasted with binocular vision, which involves the use of both eyes working together to provide depth perception and a single, combined visual field.

Monocular vision is important for tasks that only require the use of one eye, such as when looking through a microscope or using a telescope. However, it does not provide the same level of depth perception and spatial awareness as binocular vision. In some cases, individuals may have reduced visual acuity or other visual impairments in one eye, leading to limited monocular vision in that eye. It is important for individuals with monocular vision to have regular eye exams to monitor their eye health and ensure that any visual impairments are detected and treated promptly.

"Ocular physiological phenomena" is not a standardized medical term with a specific definition. However, I can provide some examples of ocular physiological phenomena, which refer to various normal functions and processes that occur in the eye. Here are a few examples:

1. Accommodation: The ability of the eye to change optical power to maintain a clear image or focus on an object as its distance varies. This is primarily achieved by changing the curvature of the lens through the action of the ciliary muscles.
2. Pupillary reflex: The automatic adjustment of the pupil's size in response to changes in light intensity. In bright light, the pupil constricts (miosis), while in dim light, it dilates (mydriasis). This reflex helps regulate the amount of light that enters the eye.
3. Tear production: The continuous secretion of tears by the lacrimal glands to keep the eyes moist and protected from dust, microorganisms, and other foreign particles.
4. Extraocular muscle function: The coordinated movement of the six extraocular muscles that control eyeball rotation and enable various gaze directions.
5. Color vision: The ability to perceive and distinguish different colors based on the sensitivity of photoreceptor cells (cones) in the retina to specific wavelengths of light.
6. Dark adaptation: The process by which the eyes adjust to low-light conditions, improving visual sensitivity primarily through changes in the rod photoreceptors' sensitivity and pupil dilation.
7. Light adaptation: The ability of the eye to adjust to different levels of illumination, mainly through alterations in pupil size and photoreceptor cell response.

These are just a few examples of ocular physiological phenomena. There are many more processes and functions that occur within the eye, contributing to our visual perception and overall eye health.

Cataract extraction is a surgical procedure that involves removing the cloudy lens (cataract) from the eye. This procedure is typically performed to restore vision impairment caused by cataracts and improve overall quality of life. There are two primary methods for cataract extraction:

1. Phacoemulsification: This is the most common method used today. It involves making a small incision in the front part of the eye (cornea), inserting an ultrasonic probe to break up the cloudy lens into tiny pieces, and then removing those pieces with suction. After removing the cataract, an artificial intraocular lens (IOL) is inserted to replace the natural lens and help focus light onto the retina.

2. Extracapsular Cataract Extraction: In this method, a larger incision is made on the side of the cornea, allowing the surgeon to remove the cloudy lens in one piece without breaking it up. The back part of the lens capsule is left intact to support the IOL. This technique is less common and typically reserved for more advanced cataracts or when phacoemulsification cannot be performed.

Recovery from cataract extraction usually involves using eye drops to prevent infection and inflammation, as well as protecting the eye with a shield or glasses during sleep for a few weeks after surgery. Most people experience improved vision within a few days to a week following the procedure.

I'm sorry for any confusion, but "Urban Population" is not a medical term. It is a demographic term used to describe the portion of a country's population that lives in areas classified as urban. The United Nations defines an urban area as a city, town, or other agglomeration with a population of 20,000 or more. However, the specific definition can vary by country and organization.

In contrast, medical terms typically refer to conditions, diseases, symptoms, treatments, or healthcare-related concepts. If you have any questions related to health or medicine, I'd be happy to help if I can!

I believe you are looking for a medical condition or term related to the state of Arizona. However, there is no specific medical condition or term named "Arizona." If you're looking for medical conditions or healthcare-related information specific to Arizona, I could provide some general statistics or facts about healthcare in Arizona. Please clarify if this is not what you were looking for.

Arizona has a diverse population and unique healthcare needs. Here are some key points related to healthcare in Arizona:

1. Chronic diseases: Arizona experiences high rates of chronic diseases, such as diabetes and cardiovascular disease, which can lead to various health complications if not managed properly.
2. Mental health: Access to mental health services is a concern in Arizona, with a significant portion of the population living in areas with mental health professional shortages.
3. Rural healthcare: Rural communities in Arizona often face challenges accessing quality healthcare due to provider shortages and longer travel distances to medical facilities.
4. COVID-19 pandemic: Like other states, Arizona has been affected by the COVID-19 pandemic, which has strained healthcare resources and highlighted existing health disparities among various populations.
5. Indigenous communities: Arizona is home to several indigenous communities, including the Navajo Nation, which faces significant health challenges, such as higher rates of diabetes, heart disease, and COVID-19 infections compared to the general population.

If you were looking for information on a specific medical condition or term related to Arizona, please provide more context so I can give a more accurate response.

Binocular vision refers to the ability to use both eyes together to create a single, three-dimensional image of our surroundings. This is achieved through a process called binocular fusion, where the images from each eye are aligned and combined in the brain to form a unified perception.

The term "binocular vision" specifically refers to the way that our visual system integrates information from both eyes to create depth perception and enhance visual clarity. When we view an object with both eyes, they focus on the same point in space and send slightly different images to the brain due to their slightly different positions. The brain then combines these images to create a single, three-dimensional image that allows us to perceive depth and distance.

Binocular vision is important for many everyday activities, such as driving, reading, and playing sports. Disorders of binocular vision can lead to symptoms such as double vision, eye strain, and difficulty with depth perception.

Pseudophakia is a medical term that refers to the condition where a person's natural lens in the eye has been replaced with an artificial one. This procedure is typically performed during cataract surgery, where the cloudy, natural lens is removed and replaced with a clear, artificial lens to improve vision. The prefix "pseudo" means false or fake, and "phakia" refers to the natural lens of the eye, hence the term "Pseudophakia" implies a false or artificial lens.

The fovea centralis, also known as the macula lutea, is a small pit or depression located in the center of the retina, an light-sensitive tissue at the back of the eye. It is responsible for sharp, detailed vision (central vision) and color perception. The fovea contains only cones, the photoreceptor cells that are responsible for color vision and high visual acuity. It has a higher concentration of cones than any other area in the retina, allowing it to provide the greatest detail and color discrimination. The center of the fovea is called the foveola, which contains the highest density of cones and is avascular, meaning it lacks blood vessels to avoid interfering with the light passing through to the photoreceptor cells.

Reproducibility of results in a medical context refers to the ability to obtain consistent and comparable findings when a particular experiment or study is repeated, either by the same researcher or by different researchers, following the same experimental protocol. It is an essential principle in scientific research that helps to ensure the validity and reliability of research findings.

In medical research, reproducibility of results is crucial for establishing the effectiveness and safety of new treatments, interventions, or diagnostic tools. It involves conducting well-designed studies with adequate sample sizes, appropriate statistical analyses, and transparent reporting of methods and findings to allow other researchers to replicate the study and confirm or refute the results.

The lack of reproducibility in medical research has become a significant concern in recent years, as several high-profile studies have failed to produce consistent findings when replicated by other researchers. This has led to increased scrutiny of research practices and a call for greater transparency, rigor, and standardization in the conduct and reporting of medical research.

Phacoemulsification is a surgical procedure used in cataract removal. It involves using an ultrasonic device to emulsify (break up) the cloudy lens (cataract) into small pieces, which are then aspirated or sucked out through a small incision. This procedure allows for smaller incisions and faster recovery times compared to traditional cataract surgery methods. After the cataract is removed, an artificial intraocular lens (IOL) is typically implanted to replace the natural lens and restore vision.

Intraocular pressure (IOP) is the fluid pressure within the eye, specifically within the anterior chamber, which is the space between the cornea and the iris. It is measured in millimeters of mercury (mmHg). The aqueous humor, a clear fluid that fills the anterior chamber, is constantly produced and drained, maintaining a balance that determines the IOP. Normal IOP ranges from 10-21 mmHg, with average values around 15-16 mmHg. Elevated IOP is a key risk factor for glaucoma, a group of eye conditions that can lead to optic nerve damage and vision loss if not treated promptly and effectively. Regular monitoring of IOP is essential in diagnosing and managing glaucoma and other ocular health issues.

Congenital nystagmus is a type of involuntary eye movement that is present at birth or develops within the first few months of life. It is characterized by rhythmic oscillations or repetitive, rapid movements of the eyes in either horizontal, vertical, or rotatory directions. These movements can impair vision and may be associated with other ocular conditions such as albinism, congenital cataracts, or optic nerve hypoplasia. The exact cause of congenital nystagmus is not fully understood, but it is believed to result from abnormal development or dysfunction in the areas of the brain that control eye movements. In some cases, congenital nystagmus may be inherited as a genetic trait. Treatment options for congenital nystagmus include corrective lenses, prism glasses, surgery, and vision therapy, depending on the underlying cause and severity of the condition.

Scleral diseases refer to conditions that affect the sclera, which is the tough, white outer coating of the eye. The sclera helps to maintain the shape of the eye and provides protection for the internal structures. Scleral diseases can cause inflammation, degeneration, or thinning of the sclera, leading to potential vision loss or other complications. Some examples of scleral diseases include:

1. Scleritis: an inflammatory condition that causes pain, redness, and sensitivity in the affected area of the sclera. It can be associated with autoimmune disorders, infections, or trauma.
2. Episcleritis: a less severe form of inflammation that affects only the episclera, a thin layer of tissue overlying the sclera. Symptoms include redness and mild discomfort but typically no pain.
3. Pinguecula: a yellowish, raised deposit of protein and fat that forms on the conjunctiva, the clear membrane covering the sclera. While not a disease itself, a pinguecula can cause irritation or discomfort and may progress to a more severe condition called a pterygium.
4. Pterygium: a fleshy growth that extends from the conjunctiva onto the cornea, potentially obstructing vision. It is often associated with prolonged sun exposure and can be removed surgically if it becomes problematic.
5. Scleral thinning or melting: a rare but serious condition where the sclera degenerates or liquefies, leading to potential perforation of the eye. This can occur due to autoimmune disorders, infections, or as a complication of certain surgical procedures.
6. Ocular histoplasmosis syndrome (OHS): a condition caused by the Histoplasma capsulatum fungus, which can lead to scarring and vision loss if it involves the macula, the central part of the retina responsible for sharp, detailed vision.

It is essential to consult an ophthalmologist or eye care professional if you experience any symptoms related to scleral diseases to receive proper diagnosis and treatment.

Glaucoma is a group of eye conditions that damage the optic nerve, often caused by an abnormally high pressure in the eye (intraocular pressure). This damage can lead to permanent vision loss or even blindness if left untreated. The most common type is open-angle glaucoma, which has no warning signs and progresses slowly. Angle-closure glaucoma, on the other hand, can cause sudden eye pain, redness, nausea, and vomiting, as well as rapid vision loss. Other less common types of glaucoma also exist. While there is no cure for glaucoma, early detection and treatment can help slow or prevent further vision loss.

The optic disk, also known as the optic nerve head, is the point where the optic nerve fibers exit the eye and transmit visual information to the brain. It appears as a pale, circular area in the back of the eye, near the center of the retina. The optic disk has no photoreceptor cells (rods and cones), so it is insensitive to light. It is an important structure to observe during eye examinations because changes in its appearance can indicate various ocular diseases or conditions, such as glaucoma, optic neuritis, or papilledema.

Intraocular lenses (IOLs) are artificial lens implants that are placed inside the eye during ophthalmic surgery, such as cataract removal. These lenses are designed to replace the natural lens of the eye that has become clouded or damaged, thereby restoring vision impairment caused by cataracts or other conditions.

There are several types of intraocular lenses available, including monofocal, multifocal, toric, and accommodative lenses. Monofocal IOLs provide clear vision at a single fixed distance, while multifocal IOLs offer clear vision at multiple distances. Toric IOLs are designed to correct astigmatism, and accommodative IOLs can change shape and position within the eye to allow for a range of vision.

The selection of the appropriate type of intraocular lens depends on various factors, including the patient's individual visual needs, lifestyle, and ocular health. The implantation procedure is typically performed on an outpatient basis and involves minimal discomfort or recovery time. Overall, intraocular lenses have become a safe and effective treatment option for patients with vision impairment due to cataracts or other eye conditions.

Depth perception is the ability to accurately judge the distance or separation of an object in three-dimensional space. It is a complex visual process that allows us to perceive the world in three dimensions and to understand the spatial relationships between objects.

Depth perception is achieved through a combination of monocular cues, which are visual cues that can be perceived with one eye, and binocular cues, which require input from both eyes. Monocular cues include perspective (the relative size of objects), texture gradients (finer details become smaller as distance increases), and atmospheric perspective (colors become less saturated and lighter in value as distance increases). Binocular cues include convergence (the degree to which the eyes must turn inward to focus on an object) and retinal disparity (the slight difference in the images projected onto the two retinas due to the slightly different positions of the eyes).

Deficits in depth perception can occur due to a variety of factors, including eye disorders, brain injuries, or developmental delays. These deficits can result in difficulties with tasks such as driving, sports, or navigating complex environments. Treatment for depth perception deficits may include vision therapy, corrective lenses, or surgery.

I'm sorry for any confusion, but "Los Angeles" is not a medical term or concept. It is a city in the state of California, USA. If you have any questions related to medical topics, I would be happy to try and help answer them!

I'm sorry for any confusion, but "Weights and Measures" is not a term that has a specific medical definition. It is a term used in various fields, including science, engineering, and commerce, to refer to systems and standards used to measure weight, length, volume, and other physical quantities.

However, if you're asking about the use of weights and measures in a medical context, it might refer to the standardized units of measurement used to quantify various aspects of health, disease, and treatment. For example:

* Weight: Measured in kilograms (kg) or pounds (lb), this is a measure of a person's mass.
* Height: Measured in meters (m) or feet/inches (ft/in), this is a measure of a person's height.
* Blood pressure: Measured in millimeters of mercury (mmHg), this is a measure of the force exerted by blood on the walls of the arteries.
* Temperature: Measured in degrees Celsius (°C) or Fahrenheit (°F), this is a measure of body temperature.
* Laboratory values: Various substances in the body, such as glucose or cholesterol, are measured in standardized units, such as millimoles per liter (mmol/L) or milligrams per deciliter (mg/dL).

These measurements help healthcare professionals assess a person's health status, diagnose medical conditions, and monitor the effects of treatment.

Aphakia, postcataract is a medical condition that refers to the absence of the lens in the eye after cataract surgery. A cataract is a clouding of the natural lens inside the eye that can cause vision loss. During cataract surgery, the cloudy lens is removed and replaced with an artificial lens implant. However, if there is a complication during the procedure and the artificial lens is not placed in the eye or if it becomes dislocated after surgery, then the patient will develop aphakia, postcataract.

Patients with aphakia, postcataract have poor vision and may experience symptoms such as blurry vision, glare, and halos around lights. They are also at an increased risk of developing glaucoma and retinal detachment. To correct the vision in patients with aphakia, they can wear special contact lenses or glasses with high-powered lenses, or undergo a secondary surgical procedure to implant an artificial lens in the eye.

The retina is the innermost, light-sensitive layer of tissue in the eye of many vertebrates and some cephalopods. It receives light that has been focused by the cornea and lens, converts it into neural signals, and sends these to the brain via the optic nerve. The retina contains several types of photoreceptor cells including rods (which handle vision in low light) and cones (which are active in bright light and are capable of color vision).

In medical terms, any pathological changes or diseases affecting the retinal structure and function can lead to visual impairment or blindness. Examples include age-related macular degeneration, diabetic retinopathy, retinal detachment, and retinitis pigmentosa among others.

A rural population refers to people who live in areas that are outside of urban areas, typically defined as having fewer than 2,000 residents and lacking certain infrastructure and services such as running water, sewage systems, and paved roads. Rural populations often have less access to healthcare services, education, and economic opportunities compared to their urban counterparts. This population group can face unique health challenges, including higher rates of poverty, limited access to specialized medical care, and a greater exposure to environmental hazards such as agricultural chemicals and industrial pollutants.

Oculocutaneous albinism (OCA) is a group of genetic disorders characterized by reduced or complete absence of melanin pigment in the eyes, skin, and hair. Melanin is the pigment responsible for giving color to our skin, hair, and eyes. OCA affects both the eyes (oculo-) and the skin (cutaneous), hence the name oculocutaneous albinism.

There are several types of OCA, each caused by different genetic mutations affecting melanin production. The most common forms include:

1. OCA1: This type is further divided into two subtypes - OCA1A and OCA1B. OCA1A is characterized by complete absence of melanin in the eyes, skin, and hair from birth. Individuals with this condition have white hair, very light skin, and pale blue or gray irises. OCA1B, on the other hand, presents with reduced melanin production, leading to lighter-than-average skin, hair, and eye color at birth. Over time, some melanin may be produced, resulting in milder pigmentation changes compared to OCA1A.
2. OCA2: This form of albinism is caused by mutations in the tyrosinase-related protein 1 (TYRP1) gene, which plays a role in melanin production. Individuals with OCA2 typically have light brown or yellowish skin, golden or straw-colored hair, and lighter irises compared to their family members without albinism.
3. OCA3: Also known as Rufous oculocutaneous albinism (ROCA), this type is caused by mutations in the tyrosinase gene (TYR). It primarily affects people of African descent, leading to reddish-brown hair, light brown skin, and normal or near-normal eye color.
4. OCA4: This form of albinism results from mutations in the membrane-associated transporter protein (MATP) gene, which is involved in melanin transport within cells. Individuals with OCA4 usually have light brown skin, yellowish or blond hair, and lighter irises compared to their family members without albinism.

Regardless of the type, all individuals with oculocutaneous albinism face similar challenges, including reduced vision due to abnormal eye development (nystagmus, strabismus, and farsightedness) and increased sensitivity to sunlight (photophobia). Proper management, such as wearing UV-protective sunglasses, hats, and sunscreen, can help protect their skin and eyes from damage.

The sclera is the tough, white, fibrous outer coating of the eye in humans and other vertebrates, covering about five sixths of the eyeball's surface. It provides protection for the delicate inner structures of the eye and maintains its shape. The sclera is composed mainly of collagen and elastic fiber, making it strong and resilient. Its name comes from the Greek word "skleros," which means hard.

A quantitative trait is a phenotypic characteristic that can be measured and displays continuous variation, meaning it can take on any value within a range. Examples include height, blood pressure, or biochemical measurements like cholesterol levels. These traits are usually influenced by the combined effects of multiple genes (polygenic inheritance) as well as environmental factors.

Heritability, in the context of genetics, refers to the proportion of variation in a trait that can be attributed to genetic differences among individuals in a population. It is estimated using statistical methods and ranges from 0 to 1, with higher values indicating a greater contribution of genetics to the observed phenotypic variance.

Therefore, a heritable quantitative trait would be a phenotype that shows continuous variation, influenced by multiple genes and environmental factors, and for which a significant portion of the observed variation can be attributed to genetic differences among individuals in a population.

Keratoconus is a degenerative non-inflammatory disorder of the eye, primarily affecting the cornea. It is characterized by a progressive thinning and steepening of the central or paracentral cornea, causing it to assume a conical shape. This results in irregular astigmatism, myopia, and scattering of light leading to blurred vision, visual distortions, and sensitivity to glare. The exact cause of keratoconus is unknown, but it may be associated with genetics, eye rubbing, and certain medical conditions. It typically starts in the teenage years and progresses into the third or fourth decade of life. Treatment options include glasses, contact lenses, cross-linking, and corneal transplantation in advanced cases.

"Twin studies" is a type of research design used in medical and scientific research, particularly in the field of genetics. This method involves comparing similarities and differences between monozygotic (identical) twins and dizygotic (fraternal) twins to estimate the heritability of certain traits or conditions.

Monozygotic twins share 100% of their genetic material, while dizygotic twins share only about 50%, similar to non-twin siblings. By comparing the concordance rates (the likelihood that both twins in a pair will have the same trait or condition) between monozygotic and dizygotic twins, researchers can estimate the proportion of variation in a trait that is due to genetic factors (heritability).

Twin studies can provide valuable insights into the genetic and environmental contributions to various traits and conditions, including physical characteristics, cognitive abilities, personality traits, and susceptibility to diseases. However, it's important to note that twin studies have limitations, such as the potential for environmental influences to be confounded with genetic factors, and the assumption that monozygotic twins share all of their genetic material, which is not always the case due to rare genetic events like mutations during development.

Thus, a person with myopia would have a negative refractive error, a person with emmetropia would have zero refractive error ... Individuals that have parents with certain refractive errors are more likely to have similar refractive errors. The Online ... which will improve vision only in the case of refractive error.[citation needed] The management of refractive error is done ... Refractive error may be quantified as the error of a wavefront arising from a person's far point, compared with a plane, or ...
... the refractive error in the weaker eye was corrected to balance the refractive error of the other eye. Strabismus surgery was ... "Wavefront excimer laser refractive surgery for adults with refractive errors". Cochrane Database Syst Rev. 6 (6): CD012687. doi ... Changes to refractive error occurring during normal age development need to be accounted for, and children have a higher risk ... it is recommended that the refractive surgery be done first. Pediatric refractive surgery involves other risks than refractive ...
Schiefer U, Kraus C, Baumbach P, Ungewiß J, Michels R (October 2016). "Refractive errors". Deutsches Ärzteblatt International. ... Premature Birth Refractive error Congenital cataract Retinopathy of prematurity Infection Congenital toxoplasmosis Congenital ...
Refractive error less than or equal to +2.00 diopters (D). Moderate: Refractive error greater than +2.00 D up to +5.00 D. High ... It is a type of refractive error. Diagnosis is based on an eye exam. Management can occur with eyeglasses, contact lenses, or ... "Facts About Refractive Errors". National Eye Institute. October 2010. Archived from the original on 28 July 2016. Retrieved 30 ... Ramjit, Sihota; Radhika, Tandon (15 July 2015). "Refractive errors of the eye". Parsons' diseases of the eye (22nd ed.). ...
"Prevalence of Refractive Errors". Archived from the original on 2016-03-05. Retrieved 2015-06-05. "Private Public Mix Working ... Prevalence of Refractive Errors in a public school children of Lahore 2. Private Public Mix Working Model of a Teaching ...
... s measure spherical refractive errors. Astigmatism can also be measured using a "clock target" with the device. A ... du Toit R, Soong K, Brian G, Ramke J (August 2006). "Quantification of refractive error: comparison of autorefractor and ... A focometer is an instrument that measures refractive errors and is intended to provide rural or economically disadvantaged ... inexpensive means for measuring refractive error in human vision. The portable, hand-held instrument is highly appropriate for ...
Weale RA (2003). "Epidemiology of refractive errors and presbyopia". Survey of Ophthalmology. 48 (5): 515-43. doi:10.1016/S0039 ... Factors causing errors or damage include internal and environmental events that induce cumulative deterioration in one or more ... Accumulation of errors: The idea that ageing results from chance events that escape proofreading mechanisms, which gradually ... The factors proposed to influence biological ageing fall into two main categories, programmed and error-related. Programmed ...
Honavar SG (2019). "The burden of uncorrected refractive error". Indian J Ophthalmol. 67 (5): 577-578. doi:10.4103/ijo.IJO_762_ ...
In the case of the eye, a large pupil emphasizes refractive error and a small pupil masks it. This phenomenon can cause a ... Because myopia is a refractive error, the physical cause of myopia is comparable to any optical system that is out of focus. ... August 2003). "Refractive error and ethnicity in children". Archives of Ophthalmology. 121 (8): 1141-7. doi:10.1001/archopht. ... Garcia CA, Oréfice F, Nobre GF, Souza D, Rocha ML, Vianna RN (June 2005). "[Prevalence of refractive errors in students in ...
Cakmak, Hasan Basri; Cagil, Nurullah; Simavlı, Hüseyin; Duzen, Betul; Simsek, Saban (February 2010). "Refractive Error May ...
"Myopia and Refractive errors in Dogs" (PDF). Investigative Ophthalmology & Visual Science. Association for Research in Vision ... Familial Aggregation of Refractive Error in Labrador Retrievers". Investigative Ophthalmology & Visual Science. 49 (11): 4784- ... In cases involving German Shepherds, Rottweilers and Miniature horses, the refraction errors were indicative of myopia. Nuclear ... laboratory investigations using retinoscopy of 240 dogs found myopic problems with varying degrees of refraction errors ...
These lenses may also correct refractive error. Although many brands of contact lenses are lightly tinted to make them easier ... most commonly by correcting refractive error. This is done by directly focusing light so it enters the eye with the proper ... Soft lenses are often used in the treatment and management of non-refractive disorders of the eye. A bandage contact lens ... He used wax to affix water-filled lenses to his eyes, neutralizing their refractive power, which he corrected with another pair ...
... is a type of refractive error due to rotational asymmetry in the eye's refractive power. This results in distorted ... 2003). "Refractive Error and Ethnicity in Children". Archives of Ophthalmology. 121 (8): 1141-7. doi:10.1001/archopht.121.8. ... An autorefractor or retinoscopy may provide an objective estimate of the eye's refractive error and the use of Jackson cross ... They also found that the TOX gene region previously identified for spherical equivalent refractive error was the second most ...
Refractive lens exchange is effectively the same procedure used to replace a lens with high refractive error when other methods ... unplanned high refractive error-either myopic or hypermetropic-due to errors in the ultrasonic biometry (measurement of the eye ... This may cause a myopic refractive error; Chronic anterior uveitis, which is a persistent inflammation of the anterior segment ... an early implant is likely to result in large refractive error later in childhood. Congenital cataracts may be caused by ...
The occluder is a simple way to focus light, as in a pinhole camera, temporarily removing the effects of refractive errors such ... This can be used to distinguish visual defects caused by refractive error, which improve when the occluder is used, from other ... Naidoo, Kovin (2002). "Case Finding in the Clinic: Refractive Errors". Comm Eye Health. 15 (43): 39-40. PMC 1705884. PMID ... Because light passes only through the center of the eye's lens, defects in the shape of the lens (errors of refraction) have no ...
Medical professionals characterize refractive errors as consequences of the eye's shape and other basic anatomy, for which no ... The book included accounts of 12 "real cases", but did not report any information about refractive error. Czech native John ... not only to refractive errors, but also to double vision, crossed-eye, lazy eye, and to more serious eye conditions such as ... Visual Training for Refractive Errors". American Academy of Ophthalmology. Archived from the original on 8 January 2016. ...
The inequality of red reflection in both the eyes indicates unequal refraction, indicating a refractive error. Pupil of a ... Congenital cataract, refractive error, ocular alignment, retinal abnormalities. Strabismus, amblyopia or amblyogenic disorder. ...
Causes include: Refractive errors Divergence insufficiency Convergence excess; this can be due to nerve, muscle, congenital or ...
It is often necessary in patients with severe refractive error who cannot undergo other refractive procedures such as LASIK or ... Clear lens extraction can be done in patients with severe refractive error and/or presbyopia who wish to avoid spectacles. ... CS1 errors: missing periodical, Eye surgery, Refractive surgeries). ... Clear lens extraction (CLE), also known as refractive lensectomy or refractive lens exchange (RLE) is a surgical procedure in ...
Does cryotherapy affect refractive error? Ophthalmology 108:343-347, 2001. Bleyl SB, Kivlin JD, et al. (2007). "Brachymesomelic ...
Additionally, ptosis can lead to eye strain and fatigue, potentially exacerbating existing refractive errors such as myopia or ... Ptosis can lead to various complications, including refractive errors. When ptosis obstructs the upper field of vision, ... which can result in astigmatism or other refractive errors due to the altered positioning of the eye. ... "Long-term outcome of refractive errors in patients with congenital blepharoptosis who have undergone ptosis surgery". Clinical ...
Refractive error can be corrected using a pinhole occluder. If the visual acuity improves with the use of pinholes, refractive ... Refractive error can be estimated via photography, a technique called photoscreening. Research has shown that optotype " ... Often, the use of such refractive lenses will correct visual acuity to normal. ...
Goyal, Ashish; Bopardikar, Ajit; Tiwari, Vijay Narayan (2018). "Estimation of Spherical Refractive Errors Using Virtual Reality ...
Refractive errors in patients with FXS are also common. Individuals with FXS are at a higher risk of developing seizures, with ...
A difference in refractive error between the eyes or the presence of astigmatism will not be accounted for. People with little ... These lenses are used when one or both eyes do not require correction of a refractive error. Some people with good natural ... The most common use is to treat refractive errors: myopia, hypermetropia, astigmatism, and presbyopia. Glasses or "spectacles" ... Astigmatism of the corrective lens: This phenomenon is called lens-induced oblique astigmatism error (OAE) or power error and ...
"Global cost of correcting vision impairment from uncorrected refractive error". Bulletin of the World Health Organization. 90 ( ... "The global cost of correcting vision impairment from uncorrected refractive error", with findings published in the Bulletin of ...
This can lead to under/overcorrection of the refractive error. In the case of the overcorrection, premature consequences of ... "LASIK Alternatives , UCLA Laser Refractive Center". UCLA Laser Refractive Center. Retrieved 2018-01-29. Zhao, LQ; Zhu, H; Li, ... those receiving PRK were less likely to achieve a refractive error, and were less likely to have an over-correction than ... Uncomplicated, successful corneal refractive surgery does not require a waiver and is noted as information only. The Navy and ...
"Wavefront excimer laser refractive surgery for adults with refractive errors". Cochrane Database Syst Rev. 6 (6): CD012687. doi ... outcomes between conventional excimer laser refractive surgery and wavefront-guided or wavefront-optimized refractive surgery, ...
He has also discovered a new refractive error called Aberropia. He has also been the first to do a combined surgery of ... Agarwal, Amar (1999). Refractive Surgery- First edition. Chennai: Jaypee, Distributed internationally by Slack and Highlights ... He is also the past President of the International Society of Refractive Surgery (ISRS) and Secretary General of the ... "Aberropia: the discovery of a new refractive entity". ophthalmologytimes.modernmedicine.com. 1 July 2007. Archived from the ...
Rubin, M.L., Surgical procedures available for influencing refractive error., in Refractive Anomalies of the Eye. 1966, US ... and high refractive errors of at least -5 to -7.5 diopters with an increase per year. There may also be changes in the fundus, ... Bores, L.D., Scleral Reinforcement, in Refractive Eye Surgery. 2001, Blackwell Science, Inc.: USA. p. 466-491. Curtin, B.J., ...
Thus, a person with myopia would have a negative refractive error, a person with emmetropia would have zero refractive error ... Individuals that have parents with certain refractive errors are more likely to have similar refractive errors. The Online ... which will improve vision only in the case of refractive error.[citation needed] The management of refractive error is done ... Refractive error may be quantified as the error of a wavefront arising from a persons far point, compared with a plane, or ...
Thats a refractive error, caused by an irregular-shaped cornea or lens. Learn how its treated. ... Refractive errors are vision problems that happen when the shape of the eye keeps you from focusing well. The cause could be ... Refractive Errors in Children (American Association for Pediatric Ophthalmology and Strabismus) * Treatment of Increasing ... Glasses or contact lenses can usually correct refractive errors. Laser eye surgery may also be a possibility. ...
... Am J Ophthalmol. 2000 Apr;129(4):427-35. doi: 10.1016/ ... Refractive error was the cause in 89.5% of the 1,236 eyes with reduced vision, amblyopia in 5%, other causes in 1.5%, with ... Purpose: To assess the prevalence of refractive errors and vision impairment in school-age children in Shunyi District, ...
Caution! children with refractive error need special attention and proper eye care consultation. Untreated refractive error in ... Uncorrected refractive error in adult will cause eye discomfort, tiredness, and sometime headache to those individuals with ... When images are not properly focused on the retina, a refractive error exists. This condition typically produces blurry vision ... Tip to avoid medication errors. *Storage And Distribution Of Medicine From Manufacturer/ Importer To User (Cold Chain Medicine) ...
MANAGEMENT OF REFRACTIVE ERRORS. Untreated refractive errors are one of the most common causes of vision loss in children in ... a refractive error may be present.. There are three main types of refractive error: myopia, hyperopia and astigmatism [See ... If refractive errors are not treated with glasses or contact lenses early enough in life, a child can be left with permanently ... This exam helps the ophthalmologist to understand if there is a refractive error and how bad it is. If needed, glasses can be ...
... with a weak positive correlation with refractive error and corneal power ... In a myopic adult population the more myopic error measured the steeper the cornea was, ... Relation of refractive error with corneal curvature of the eye in adult subjects with refractive error. J Evol Med Dent Sci. ... Correlation between refractive error, corneal power, and thickness in a large population with a wide range of ametropia. Invest ...
... we were able to identify content areas and aspects of visual functioning in persons with refractive error that are not measured ... Development of the National Eye Institute refractive error correction quality of life questionnaire: focus groups Ophthalmology ... The distribution of comments by topic domain was generally similar across types of correction and type of refractive error. The ... The similarity of problems mentioned across refractive error type and correction method suggests it will be possible to develop ...
MANAGEMENT OF REFRACTIVE ERRORS. Untreated refractive errors are one of the most common causes of vision loss in children in ... a refractive error may be present.. There are three main types of refractive error: myopia, hyperopia and astigmatism [See ... If refractive errors are not treated with glasses or contact lenses early enough in life, a child can be left with permanently ... This exam helps the ophthalmologist to understand if there is a refractive error and how bad it is. If needed, glasses can be ...
... is a condition that causes blurred vision when light rays entering the eye meet in front of ... In most cases, refractive errors represent a natural variation from normal vision and are not considered a disease. ... Nearsightedness, farsightedness, astigmatism, and presbyopia are common refractive errors.. Vision usually can be corrected ...
Uncorrected refractive errors can negatively affect functioning, quality of life, and work productivity.2 Refractive errors ... even at low levels of refractive error.3. Across military populations, refractive errors have multiple implications for ... Refractive surgery procedures after entering the military may also influence the prevalence of refractive errors. For example, ... The data presented here allow for ongoing monitoring of refractive error to direct interventions such as refractive surgery. ...
Facts about refractive errors. https://www.nei.nih.gov/learnabout-eye-health/eye-conditions-and-diseases/refractive-errors ... Refractive Disorders. US Ophthalmic Pipeline and Clinical Trials. Investigator-Sponsored Trials & Medical Education Grants. ...
Development and Management of Refractive Error in Childhood. Publication. Publication. Ontwikkeling en behandeling van ... Polling, J.R. (2021, September 22). Development and Management of Refractive Error in Childhood. Erasmus University Rotterdam. ...
There is still much that should be done to alleviate the problem of uncorrected refractive error. ... The cost to train refractionists and maintain refractive services to deal with uncorrected refractive error (including ... Uncorrected distance refractive error leading to vision impairment can reduce quality of life4 and decrease participation in ... Refractive error affects people of all ages, socio-economic status and ethnic groups. The most recent statistics estimate that ...
Refractive Cataract residual refractive error refractive outcomes refractive surgery LASIK PRK SMILE limbal relaxing incision ... Cylinder and Refractive Error- LASIK, PRK, SMILE and LRIs to Resolve Refractive Errors Following Cataract Surgery ... Home Clinical Education Cylinder and Refractive Error- LASIK, PRK, SMILE and LRIs to Resolve Refractive Errors Following ... What Im Doing Differently This Year: Piggyback Lenses for Residual Refractive Error ...
B) Distribution of refractive error in children at 11 years old or less and their parents. (C) Distribution of refractive error ... Preoperative refractive error was used in 13 parents who had previously undergone refractive surgery. Besides refractive ... only the childrens non-cycloplegic refractive error, and the parents and grandparents binary refractive error state (myopia or ... of the parental refractive error was obtained through self-reporting. However, analysis for RED with both parents refractive ...
653F,653L,653Z,703F,Abdelghany,Alio,ciliary sulcus,DUET,piggyback,pseudophakic,refractive,refractive enhancement,refractive ... Home , Eye Science , Surgical options for correction of refractive error following cataract surgery ... Surgical options for correction of refractive error following cataract surgery. Posted on 1/10/2014 ...
Significantly higher hyperopic refractive errors were found in eyes with pterygium ≥3 mm reaching or not pupillary margin. ... Pterygium in adults from the Brazilian Amazon Region: prevalence, visual status and refractive errors ... Pterygium in adults from the Brazilian Amazon Region: prevalence, visual status and refractive errors ... its role as main cause of unilateral and bilateral visual impairment and blindness and its impact on refractive errors from ...
... required to provide care to all individuals who currently have vision impairment resulting from uncorrected refractive error ( ... The cost of establishing and operating the educational and refractive care facilities required to deal with vision impairment ... The global cost of educating the additional personnel and of establishing, maintaining and operating the refractive care ... To estimate the global cost of establishing and operating the educational and refractive care facilities ...
ciliary sulcus,DUET,Finkelman,Levinger,Mimouni,piggyback,pseudophakic,refractive error,refractive surprise,secondary,Shahar, ... Outcomes of refractive error correction in pseudophakic patients using a sulcus piggyback intraocular lens. Posted on 5/07/2020 ... Home , Eye Science , Outcomes of refractive error correction in pseudophakic patients using a sulcus piggyback intraocular lens ...
Refractive errors are failure of the eye to focus images sharply on the retina, causing blurred vision (see figure Errors of ...
... uncorrected refractive error is the leading cause of vision impairment. Most people can see again with a correctly-prescribed ... What is refractive error?. Refractive error is a very common eye disorder that occurs when the eye cannot focus clearly. This ... Refractive error. Globally, uncorrected refractive error is the main cause of vision impairment. Most people can see again with ... A refractive error happens when the eye is shaped in such a way that light cannot be sharply focused on the retina. There are ...
I believe that refractive error is a disease of the eye-no different from glaucoma, dry eye disease, and other issues for which ... Refractive error is a disease of the eye, and we should treat it.. Ehsan Sadri, MD, FACS, FAAO ... Cataract & Refractive Surgery Today Global , Europe Edition delivers cutting-edge information to cataract and refractive ... Refractive error is a disease of the eye, and we should treat it. ... Refractive Surgery. Navigating a History of Refractive Surgery ...
Regression equation for difference in spherical refractive error versus mean spherical refractive error: difference y = (0.74 ... Regression equation for difference in spherical refractive error versus mean spherical refractive error: difference y = (0.74 ... Regression equation for difference in spherical refractive error versus mean spherical refractive error: difference y = (0.74 ... Regression equation for difference in spherical refractive error versus mean spherical refractive error: difference y = (0.74 ...
Children were screened for refractive errors and compared with the refractive errors data of different children of same age ... Introduction: Refractive errors cannot be prevented, but it is important to detect them early to improve the quality of life ... Clinical Profile of Refractive Errors Associated with Screen Time in Children Aged 5-15 Years in a Tertiary Care Hospital of ... Conclusion: Refractive errors increased due to smart classes in schools or use of laptops, television viewing, computers or ...
Refractive Errors. Refractive errors are the most frequent eye problems in the United States. Refractive errors include myopia ... The National Eye Institute states that proper refractive correction could improve vision among 150 million Americans. Learn ...
Surgeries are available for correction of refractive error as in very high power and as an option for those who want to get rid ... The refractive errors can be corrected by prescribing glasses, contact lenses and corrective surgeries. There are certain ...
However, some may have very unequal eyes, with refractive error in one eye only, refractive error in both eyes but much ... Although most people have a consistent type of refractive error, such as being "near sighted", refractive errors may also be a ... Types of Refractive Error. Myopia: Also known as nearsightedness, myopia is the inability to see clearly at distance while ... If the image is not focused on the retina correctly, then the image is blurred and a refractive error is present. ...
Refractive Errors. Refractive errors are a common eye condition that occurs when the eyes shape prevents light from focusing ... What causes refractive errors?. A refractive error can happen as a result of one, or a few, of the following:. *A change in the ... How are refractive errors diagnosed?. All types of refractive errors can be found with a general eye exam, including a:. * ... What are the types of refractive errors?. The term "refractive errors" refers to four conditions:. *Astigmatism. Objects up ...
NAd NA Treatment of refractive error Most refractive errors are easily treatable by appropriate refractive correction. However ... Detection of refractive error Refractive error can be detected through routine examination of patients who present to clinics, ... 238 Impact of refractive error blindness Blindness due to uncorrected or inadequately corrected natural refractive error starts ... Reliable data on the prevalence of blindness due to refractive error and the distribution of refractive error obtained from ...
Refractive Error. Details Written by Harbor View Eye Care Team Published: 24 August 2016 A refractive error occurs when light ... Surgery and corneal molding may also be options for the correction of refractive errors. ... Glasses and contact lenses are made to bend light at a precise angle to offset the error that occurs in your eye. ...
  • As myopia has been identified as the most prevalent refractive error all over the world, 10 , 11 the correlation between myopia and axial length of the eye was extensively discussed, revealing a positive correlation between the absolute value of myopia and axial length. (dovepress.com)
  • During 2001-2018, myopia and astigmatism were the most common refractive errors at 1.4 million and 1.2 million incident diagnoses, respectively, among active component service members of all occupational groups. (health.mil)
  • 1 Vision impairment has been defined based on distance visual acuity only, and uncorrected distance refractive error (mainly myopia) is the single biggest cause of worldwide vision impairment. (cehjournal.org)
  • There are several types of refractive error, including myopia (short-sight or near-sight) and hyperopia (long-sight or far-sight). (hollows.org.nz)
  • Refractive errors include myopia (near-sightedness), hyperopia (farsightedness), astigmatism (distorted vision at all distances), and presbyopia that occurs between age 40-50 years (loss of the ability to focus up close, inability to read letters of the phone book, need to hold newspaper farther away to see clearly) can be corrected by eyeglasses, contact lenses, or in some cases surgery. (cdc.gov)
  • Myopia, or nearsightedness , is the most common refractive error and occurs when the eyeball is too long or the cornea is too curved for the length of the eyeball. (lindavision.com)
  • Three most common refractive errors in children are Myopia (nearsightedness), Hyperopia (farsightedness) and Astigmatism - a sight disorder in which a child's eye doesn't focus image evenly owing to the irregular shape of the cornea. (kidseyeconsult.com)
  • Certain types of refractive errors are more likely to occur in a family with a history of eye disorders, such as myopia . (booksbetween.com)
  • The most common types of refractive error are near-sightedness, far-sightedness, astigmatism, and presbyopia. (wikipedia.org)
  • They are frequently categorized as spherical errors and cylindrical errors: Cylindrical errors cause astigmatism, when the optical power of the eye is too powerful or too weak across one meridian, such as if the corneal curvature tends towards a cylindrical shape. (wikipedia.org)
  • Astigmatism: A person with astigmatic refractive error sees lines of a particular orientation less clearly than lines at right angles to them. (wikipedia.org)
  • Vision amendment medical procedure is expected to remove the eye refractive mistakes, for example, nearsightedness (partial blindness), hyperopia (farsightedness), astigmatism and presbyopia. (bazarbay.net)
  • In the world of modern cataract and refractive surgery, we have the capability to correct visual acuity that is compromised due to astigmatism and other types refractive error, so why shouldn't we treat astigmatism during cataract surgery? (crstodayeurope.com)
  • Astigmatism is an irregular shape of the refractive surfaces of the eye, most commonly the cornea but sometimes also the lens. (pedopnj.com)
  • Although most people have a consistent type of refractive error, such as being "near sighted", refractive errors may also be a combination of problems such as myopic astigmatism or hyperopic astigmatism. (pedopnj.com)
  • The distribution of comments by topic domain was generally similar across types of correction and type of refractive error. (nih.gov)
  • Farsightedness (also called hyperopia) is a common type of refractive error where distant objects may be seen more clearly than objects that are near. (savesightcentre.com)
  • Optometrists can prescribe the appropriate treatment for the specific type of refractive error you have. (booksbetween.com)
  • They might need partial or full correction, depending on the type of refractive error. (specsmart.ng)
  • Refractive error, also known as refraction error, is a problem with focusing light accurately on the retina due to the shape of the eye and or cornea. (wikipedia.org)
  • An eye that has no refractive error when viewing distant objects is said to have emmetropia or be emmetropic meaning the eye is in a state in which it can focus parallel rays of light (light from distant objects) on the retina, without using any accommodation. (wikipedia.org)
  • Spherical errors occur when the optical power of the eye is either too large or too small to focus light on the retina. (wikipedia.org)
  • When images are not properly focused on the retina, a refractive error exists. (myhealth.gov.my)
  • If light rays are not focused well on the retina, a refractive error may be present. (aapos.org)
  • Refractive error is a condition that causes blurred vision when light rays entering the eye meet in front of or behind the retina rather than directly on it. (alberta.ca)
  • 1 Refractive errors occur when the focusing power of the eye does not allow for a sharp image on the retina, resulting in a blurred image and loss of detail. (health.mil)
  • A refractive error happens when the eye is shaped in such a way that light cannot be sharply focused on the retina. (hollows.org.nz)
  • If the image is not focused on the retina correctly, then the image is blurred and a refractive error is present. (pedopnj.com)
  • A refractive error occurs when light is not focused properly on the retina at the back of the eye. (harborvieweye.com)
  • Refractive Errors occur when the shape of the eye prevents light from focusing directly on the retina. (savesightcentre.com)
  • Refractive error occurs when the shape of your eye is not optimal for focusing light directly on the retina. (booksbetween.com)
  • Essentially, these errors are typically caused by the eye's inability to focus light accurately onto the retina due to its shape. (kyeye.com)
  • If light rays fail to focus directly on the retina, a Refractive Error is present. (specsmart.ng)
  • Blurred vision results from a refractive error, which occurs when the eye cannot focus correctly, and the retina does not get a sharp image. (sriramakrishnahospital.com)
  • Three aspects of eye anatomy become primary causes of refractive errors , or the eye's inability to refract or focus light precisely on the retina. (sriramakrishnahospital.com)
  • Some have been proposed as suitable instruments for use in screening programs, to detect children with or at risk for amblyopia or strabismus associated with high refractive errors. (arvojournals.org)
  • Also, if a child's refractive errors are not addressed timely, amblyopia (lazy eye) might develop. (eyecraftersny.com)
  • These children are at risk of developing "lazy eye" or amblyopia in the eye with a higher refractive error. (pedopnj.com)
  • Even smaller hemangiomas can cause refractive errors or amblyopia, and oftentimes need to be treated with either systemic or topical therapy depending on the size and extent," she said. (medscape.com)
  • Currently, presbyopia can be corrected by refractive surgery (LASIK). (myhealth.gov.my)
  • The cost to train refractionists and maintain refractive services to deal with uncorrected refractive error (including presbyopia) is US $28 billion. (cehjournal.org)
  • The similarity of problems mentioned across refractive error type and correction method suggests it will be possible to develop a single questionnaire with adequate content validity to compare the impact of different modes of correction in vision-targeted, health-related quality of life. (nih.gov)
  • Optimal visual performance in the setting of refractive error usually requires correction, either through eyeglasses, contact lenses, or refractive surgery. (health.mil)
  • Conclusions Pterygium was highly prevalent and the second cause of visual impairment and blindness after provision of refractive correction. (bmj.com)
  • The National Eye Institute states that proper refractive correction could improve vision among 150 million Americans. (cdc.gov)
  • Surgeries are available for correction of refractive error as in very high power and as an option for those who want to get rid of glasses. (pinkcityretina.com)
  • Refractive error blindness Rakhi Dandona1 & Lalit Dandona2 Recent data suggest that a large number of people are blind in different parts of the world due to high refractive error because they are not using appropriate refractive correction. (studyres.com)
  • In addition to blindness due to naturally occurring high refractive error, inadequate refractive correction of aphakia after cataract surgery is also a significant cause of blindness in developing countries. (studyres.com)
  • Because of the increasing realization of the enormous need for correction of refractive error worldwide, this condition has been considered one of the priorities of the recently launched global initiative for the elimination of avoidable blindness: VISION 2020 - The Right to Sight (14, 15). (studyres.com)
  • Definition of blindness Ref. No. 00-1034 Blindness is defined either in terms of best-corrected distance visual acuity (the most appropriate refractive correction) or presenting distance visual acuity (the individual's current refractive correction) in the better eye. (studyres.com)
  • Surgery and corneal molding may also be options for the correction of refractive errors. (harborvieweye.com)
  • Due to increasing realization of enormous need for correction of refractive error worldwide, refractive error has been considered one of the priorities in the category of preventable blindness. (biomedjournal.com)
  • Each of these refractive errors brings its own set of challenges and requires a unique approach for correction. (kyeye.com)
  • Undercorrected refractive error was defined as improvement of better eye visual acuity of at least 2 lines or more with best possible refractive correction. (johnshopkins.edu)
  • Or should I sort of let it ride and let nature take its course, and there's no need to provide refractive correction? (optometrytimes.com)
  • I think we've learned a lot from research in the past 20 to 30 years, that helped guide those kinds of decisions about the timing, the amount of refractive error, the amount of correction to provide to these patients when it is required. (optometrytimes.com)
  • Refractive error was the principal cause (94.2%) of impaired vision and 88% of children who could achieve VA ≥6/9 with best correction were without necessary spectacles . (bvsalud.org)
  • Refractive errors are corrected with eyeglasses, contact lenses, or surgery. (wikipedia.org)
  • Glasses or contact lenses can usually correct refractive errors. (medlineplus.gov)
  • Refractive error can be treated with glasses, contact lenses, or surgery. (hollows.org.nz)
  • The refractive errors can be corrected by prescribing glasses, contact lenses and corrective surgeries. (pinkcityretina.com)
  • Corrective lenses, whether as glasses or contact lenses, are necessary for children with refractive errors to correct vision and ensure that a child will achieve the best vision as possible as an adult. (pedopnj.com)
  • A variety of refractive surgery techniques, which reshape the corneal stroma using laser energy, have been marketed as simple and safe alternatives to glasses or contact lenses. (aafp.org)
  • Over the past two decades, a variety of refractive surgery techniques have been developed and marketed as simple and safe alternatives to glasses or contact lenses. (aafp.org)
  • Glasses and contact lenses are made to bend light at a precise angle to offset the error that occurs in your eye. (harborvieweye.com)
  • One of the ways that Dr. Vu can fix refractive errors is through orthokeratology , or the process of using special contact lenses to temporarily reshape the cornea. (lindavision.com)
  • Light-bending contact lenses cure refractive problems. (savesightcentre.com)
  • While a mild errors can go untreated, more serious ones require the use of contact lenses, glasses, or surgery. (booksbetween.com)
  • Contact lenses can only correct certain types of refractive errors, not all. (booksbetween.com)
  • Refractive surgery permanently changes the shape of the cornea. (wikipedia.org)
  • What Is Refractive Surgery? (medlineplus.gov)
  • Five hundred microns has been accepted as a cut-off value for safe refractive surgery. (dovepress.com)
  • Future analyses should focus on the specific effects of military refractive surgery programs on the readiness of service members. (health.mil)
  • This article updates previous reports and focuses on the types of refractive error amenable to refractive surgery interventions. (health.mil)
  • The data presented here allow for ongoing monitoring of refractive error to direct interventions such as refractive surgery. (health.mil)
  • Although there are few high-quality prospective studies of long-term outcomes, complications, or stability for refractive surgery procedures, there is at least general agreement that more than 90% of appropriately selected patients achieve excellent uncorrected distance vision. (aafp.org)
  • Its popularity in this country has decreased from a peak of 1,400,000 procedures in 2006 for reasons that are not entirely clear, although millions of persons worldwide, particularly in Asia, still choose refractive surgery. (aafp.org)
  • There are few high-quality prospective studies of refractive surgery. (aafp.org)
  • Overall, there is general agreement that refractive surgery is safe and effective. (aafp.org)
  • Most studies reporting on subjective complaints lack objective data concerning persistently bothersome symptoms, and cannot distinguish between refractive error remaining after surgery and adverse effects of the surgery itself. (aafp.org)
  • Glasses fix refractive problems and improve vision without surgery. (savesightcentre.com)
  • Refractive surgery may eliminate the need for glasses or contacts. (savesightcentre.com)
  • However, if you have a more severe refractive error, you may consider undergoing surgery. (booksbetween.com)
  • There are several different types of treatments for refractive errors, including corrective surgery. (booksbetween.com)
  • Excerpted from BCSC 2020-2021 series: Section 13 - Refractive Surgery . (aao.org)
  • Interruptions in access to care have also proven a huge burden across the NCD spectrum, creating backlogs for preventive care and treatments such as cataract surgery and refractive error services. (who.int)
  • Dr Waring presented the next generation of postoperative refractive adjustment, which is performed by our preferred instrument in cataract surgery: the femtosecond laser. (medscape.com)
  • In many low- and middle-income countries, it is necessary to provide refractive services at all levels of the health care system, especially at primary level, where services are provided in the community. (cehjournal.org)
  • Social enterprise (SE) solutions provide refractive error services while at the same time alleviating poverty and providing employment opportunities. (cehjournal.org)
  • Approximately 47 000 additional full-time functional clinical refractionists and 18 000 ophthalmic dispensers would be required to provide refractive care services for these individuals. (iapb.org)
  • Eyeglasses correct refractive problems. (savesightcentre.com)
  • Eye doctors use precise measurements for the lenses in eyeglasses to change the refractive focal point. (booksbetween.com)
  • Refractive errors were based We assessed the records of 265 patients to diplopia, diminished visual acuity on spherical equivalents (sphere +1/2 with vertical strabismus (130 males and and palpebral fissure changes [6]. (who.int)
  • 0.5 logarithm of the minimal angle of resolution (logMAR) and/or strabismus and/or any refractive error were analysed. (lu.se)
  • 0.5 logMAR) was found in 32 (14%), strabismus in 82 (38%), refractive errors in 114 (52%) and significant eye problem in 143 (65%) children. (lu.se)
  • An additional week of GA at birth reduced the risk for refractive errors, strabismus and significant eye problems. (lu.se)
  • Visual acuity (VA), refractive errors and strabismus, together with visual impairment (VI) and any significant eye problem, defined as VA >0.5 logarithm of the minimal angle of resolution (logMAR) and/or strabismus and/or any refractive error were analysed. (lu.se)
  • The aim of the present study was to show the prevalence of refractive error in early years of life from urban and rural background. (biomedjournal.com)
  • Understanding refractive errors, their causes, symptoms, and consequences, empowers you to make informed decisions about your eye health. (kyeye.com)
  • We train our eye doctors and eye nurses to treat refractive error. (hollows.org.nz)
  • A doctor will help us correct refractive errors by adjusting our eyes to allow for better vision. (booksbetween.com)
  • Missing the target refraction by one diopter (or even less) might lead to significant dissatisfaction and to the search for measures to deal with the residual refractive error. (medscape.com)
  • The readings underestimated the amount of hypermetropic or astigmatic refractive error found on retinoscopy by an amount proportional to the magnitude of the refractive error. (arvojournals.org)
  • Refractive errors are a common eye condition that occurs when the eye's shape prevents light from focusing directly on the back of the eye, resulting in blurry vision among other symptoms. (eyecraftersny.com)
  • Refractive errors can generate different symptoms according on their nature and severity. (savesightcentre.com)
  • While most refractive errors have similar symptoms, you should have an eye examination to determine the exact cause of your condition. (booksbetween.com)
  • The World Health Organization's Global Action Plan for 2014 to 2019 has identified human resources for refractive error as a priority in reducing avoidable blindness globally. (cehjournal.org)
  • Aims To determine prevalence of pterygium, its role as main cause of unilateral and bilateral visual impairment and blindness and its impact on refractive errors from adults living in a high ultraviolet exposure area in the Brazilian Amazon Region. (bmj.com)
  • Refractive error as a cause of blindness has been recognized only recently with the increasing use of presenting visual acuity for defining blindness. (studyres.com)
  • Blindness due to refractive error in any population suggests that eye care services in general in that population are inadequate since treatment of refractive error is perhaps the simplest and most effective form of eye care. (studyres.com)
  • Strategies such as vision screening programmes need to be implemented on a large scale to detect individuals suffering from refractive error blindness. (studyres.com)
  • Also adequate infrastructure has to be developed in underserved areas of the world to facilitate the logistics of providing affordable reasonable-quality spectacles to individuals suffering from refractive error blindness. (studyres.com)
  • Long-term success in reducing refractive error blindness worldwide will require attention to these issues within the context of comprehensive approaches to reduce all causes of avoidable blindness. (studyres.com)
  • Introduction Refractive error as a cause of blindness has not received much attention because many definitions of blindness have been based on best-corrected distance visual acuity, including the definition used in the International Statistical Classification of Diseases and Related Health Problems (1). (studyres.com)
  • However, in many parts of the world refractive error would become the second largest cause of treatable blindness after cataract if blindness were defined on the basis of presenting distance visual acuity (2-10). (studyres.com)
  • For the most part, refractive error can be easily corrected with spectacles, which makes it imperative that effective strategies be developed to eliminate this easily treatable cause of blindness. (studyres.com)
  • This review presents a summary of the current and likely future issues related to blindness due to refractive error. (studyres.com)
  • The latter definition permits assessment of blindness due to refractive error, whereas the former does not. (studyres.com)
  • Although a large amount of data are available on the prevalence of blindness in different parts of the world (16), data on the prevalence of blindness due to refractive error are not readily available because the presenting distance visual acuity definition is not always used. (studyres.com)
  • If this does not work, refractive errors can lead to blindness. (booksbetween.com)
  • Refractive errors can result in poor vision or even blindness, so it is important to seek medical help for any vision problems. (booksbetween.com)
  • A person being blind due to refractive error in young age suffers more blind years than an old person with cataract blindness. (biomedjournal.com)
  • The number of people with refractive errors that have not been corrected was estimated at 660 million (10 per 100 people) in 2013. (wikipedia.org)
  • People with refractive error frequently have blurry vision. (wikipedia.org)
  • Glasses have been a time-tested method for correcting refractive errors. (kyeye.com)
  • Pinhole glasses have been marketed as a visual therapy device, with the claim that continuous use of these glasses will improve refractive error. (iium.edu.my)
  • Aim: The purpose of this study was to compare the refractive error of myopic participants before and after wearing the pinhole glasses for 3 weeks. (iium.edu.my)
  • Results: The refractive error before and after the intervention was then being compared and the results showed that there was no significant difference in refractive error of both right (p= 0.08) and left eyes (p= 0.09) of myopic participants before and after wearing the pinhole glasses. (iium.edu.my)
  • Conclusion: Our results suggest that pinhole glasses did not improve the refractive error of myopic participants. (iium.edu.my)
  • If you need glasses or contacts to correct the blurriness of distant or up-close objects, there is a refractive defect in your eyes. (sriramakrishnahospital.com)
  • To find out the correlation between myopic refractive error, corneal power and central corneal thickness (CCT) in the adult Egyptian population. (dovepress.com)
  • Conclusions : Longer time spent on near work, including doing homework, reading books and drawing, and on digital devices including mobile phone and handheld electronic devices were associated with more myopic refractive power in Hong Kong preschool children. (edu.hk)
  • Refractive errors are vision problems that happen when the shape of the eye keeps you from focusing well. (medlineplus.gov)
  • To assess the prevalence of refractive errors and vision impairment in school-age children in Shunyi District, northeast of Beijing, the Peoples Republic of China. (nih.gov)
  • To identify the content area for a questionnaire designed to measure the vision-targeted, health-related quality of life for persons with well-corrected refractive error. (nih.gov)
  • Using focus groups, we were able to identify content areas and aspects of visual functioning in persons with refractive error that are not measured by standard visual acuity testing in the clinic or by other vision-targeted, health-related quality of life instruments such as the 25- or 51-item National Eye Institute-Visual Functioning Questionnaire. (nih.gov)
  • In most cases, refractive errors represent a natural variation from normal vision and are not considered a disease. (alberta.ca)
  • Refractive errors are a common cause of impaired vision. (health.mil)
  • Uncorrected distance refractive error is the biggest single cause of vision impairment worldwide. (cehjournal.org)
  • From research it was estimated that the number of people with vision impairment due to uncorrected distance refractive error was 107.8 million, 1 and the number of people affected by uncorrected near refractive error was 517 million, 2 giving a total of 624.8 million people. (cehjournal.org)
  • Uncorrected distance refractive error leading to vision impairment can reduce quality of life 4 and decrease participation in daily activities that are vision-related. (cehjournal.org)
  • Despite being one of the more easily corrected conditions resulting in vision impairment, uncorrected refractive error still remains a significant cause of vision impairment globally. (cehjournal.org)
  • To estimate the global cost of establishing and operating the educational and refractive care facilities required to provide care to all individuals who currently have vision impairment resulting from uncorrected refractive error (URE). (iapb.org)
  • The cost of establishing and operating the educational and refractive care facilities required to deal with vision impairment resulting from URE was a small proportion of the global loss in productivity associated with that vision impairment. (iapb.org)
  • An eye vision rectification medical procedure is required on the off chance that you need a changeless arrangement against the refractive blunders. (bazarbay.net)
  • Globally, uncorrected refractive error is the main cause of vision impairment. (hollows.org.nz)
  • Early diagnosis of refractive errors is particularly essential for children, because a child's academic progress can be affected by poor vision. (eyecraftersny.com)
  • Refractive errors are among the most common vision issues, and you may be at higher risk if you have family members diagnosed with one. (eyecraftersny.com)
  • Here, Dr. Linda Vu explains what you need to know about refractive errors and how she can treat them at her Los Angeles vision center. (lindavision.com)
  • To discuss orthokeratology and other solutions to refractive errors, please contact Linda Vision today by calling (626) 382-2020 and request a consultation with Dr. Vu. (lindavision.com)
  • Vision abnormalities like different 'Refractive errors' could be detected well in time at an early & curable age. (kidseyeconsult.com)
  • This is a safe and straightforward method, and most refractive errors are compensated with appropriate lenses to give your child the correct vision and comfort. (kidseyeconsult.com)
  • To diagnose and treat refractive problems in youngsters, vision must be monitored regularly. (savesightcentre.com)
  • Refractive errors affect the vision of a person who suffers from the condition. (booksbetween.com)
  • To understand the causes of refractive errors, one needs to first understand vision itself. (booksbetween.com)
  • Refractive errors are by far the commonest cause of defective vision in school childrens. (biomedjournal.com)
  • 2010). School health is a part of vision 2020 program targeting school children for evaluating refractive error and vitamin A deficiency (Batra et al. (biomedjournal.com)
  • Yet, how many truly understand what refractive errors are and how they affect our vision? (kyeye.com)
  • Refractive errors represent one of the most common vision problems people encounter worldwide. (kyeye.com)
  • They can diagnose refractive errors through a routine eye exam that includes vision testing and eye health evaluation. (kyeye.com)
  • Refractive errors are not a life sentence for blurred vision. (kyeye.com)
  • In Bates System of Eye Exercise, it is claimed that eye exercise can restore vision with refractive error by completely relaxing the eyes. (iium.edu.my)
  • Refractive errors are a vision problem that makes it hard to see things. (sriramakrishnahospital.com)
  • The vision examination is designed to test distance vision in sample persons (SPs) aged 12 years and older, measure refractive error, measure the shape of the cornea and, if applicable, measure the distance eyeglass prescription in SP's aged 12 years and older. (cdc.gov)
  • In children, refractive errors are the most common vision disorders, occurring in 20 percent by 16 years of age. (cdc.gov)
  • Additionally, all SPs will be administered two other tests which require automated vision equipment: a Visual Acuity test, which tests for distance vision, and an Objective Refraction/Keratometric evaluation, which measures the SP's refractive error and corneal curvature. (cdc.gov)
  • Reduced vision because of uncorrected refractive error is a public health problem among school -age children in Bhutan . (bvsalud.org)
  • other causes (14%)5 including low vision and refractive errors. (who.int)
  • At least, this was the impression that George O. Waring IV, MD, left on me during his presentation [ 1 ] on refractive index shaping (RIS) at this year's American Academy of Ophthalmology meeting. (medscape.com)
  • Thinner corneas are at risk for ectasia, haze and less predictable refractive outcomes. (dovepress.com)
  • Since there are many types of Refractive Eye Surgeries, our doctors decide what best suits your child's eye, based on medical conditions and parents prefered choice/consent. (kidseyeconsult.com)
  • This can arise from a cornea or crystalline lens with not enough curvature (refractive hyperopia) or an eyeball that is too short (axial hyperopia). (wikipedia.org)
  • If your cornea or lens isn't evenly and smoothly curved, light rays aren't refracted properly, and you have a refractive error. (mayoclinic.org)
  • Factors that can cause refractive errors include changes in the eye's cornea and lens, as well as length and shape. (booksbetween.com)
  • Refractive errors in the eye are caused by the shape of the eyeball, the cornea, or the aging lens. (booksbetween.com)
  • Other causes of the refractive error include aging of the lens or cornea and developmental factors. (booksbetween.com)
  • It reminded me of our own experience with a technique that tries to correct residual refractive errors: the light-adjustable lens. (medscape.com)
  • In a process called "phase wrapping," a convex lens is reduced by the femtosecond laser to a thin layer of approximately 50 μm in thickness, creating multiple refractive zones. (medscape.com)
  • Laser in situ keratomileusis (LASIK), since its introduction by Pallikaris and his team in 1990, 1 has become the most frequently performed corneal refractive procedure all over the world, with millions of LASIK procedures completed to date. (dovepress.com)
  • LASIK, PRK, and SMILE are refractive operations. (savesightcentre.com)
  • This presentation is from the session "RD-5 - Session V: Post - op Strategies To Improve IQ" from the 2022 ASCRS Refractive Day held on April 22, 2022 in Washington, DC. (ascrs.org)
  • Graham Erickson, OD, FAAO, FCOVD, shares highlights from his 2022 American Academy of Optometry presentation, 'Evidence-based refractive prescribing for pediatric patients. (optometrytimes.com)
  • Graham Erickson, OD, FAAO, FCOVD, professor at Pacific University in Oregon, speaks with Optometry Times®' Kassi Jackson on highlights from his discussion titled, 'Evidence-based refractive prescribing for pediatric patients,' which he presented during the 2022 American Academy of Optometry (AAOpt) annual meeting in San Diego. (optometrytimes.com)
  • He's here to share highlights from his discussion titled, 'Evidence-based refractive prescribing for pediatric patients,' which he's presenting during the 2022 American Academy of Optometry meeting this year in San Diego. (optometrytimes.com)
  • Refractive error is a very common eye disorder that occurs when the eye cannot focus clearly. (hollows.org.nz)
  • Refractive error is also one of the most common causes of visual impairment (3-5, 9-13). (studyres.com)
  • Refractive errors are so common that, according to the National Eye Institute, most people have one or more. (lindavision.com)
  • Refractive error is one of the most common determinants of visual impairment worldwide particularly among children and frequently remains undiagnosed for long period. (biomedjournal.com)
  • Undercorrected refractive error rates were more common in older adults who had completed fewer years of education and in those who had cataract. (johnshopkins.edu)
  • The undercorrected refractive error rate among Singaporean Chinese is relatively common compared with data from other populations. (johnshopkins.edu)
  • And one of the biggest areas as optometrist that we have to contend with is refractive error, because it is common to find refractive errors in our young patients. (optometrytimes.com)
  • children with refractive error need special attention and proper eye care consultation. (myhealth.gov.my)
  • Untreated refractive error in children may lead to ambyopia (lazy eye). (myhealth.gov.my)
  • Aims To report the refractive error difference (RED) between parents and their children and the estimated single generational myopic shift in an urban area in China. (bmj.com)
  • 5 However, few studies have reported the quantitative relation between refractive errors in parents and their children. (bmj.com)
  • Kid's eye consult is a dedicated facility for all refractive errors and cataract conditions present of children. (kidseyeconsult.com)
  • We have the best child eye care expertise and long experience of correcting refractive errors in children at kids Eye Consult . (kidseyeconsult.com)
  • Purpose : This cross-sectional study aimed to investigate the refractive error in Hong Kong preschool children and its association with near work (including digital device usage) among these children. (edu.hk)
  • abstract = "Purpose : This cross-sectional study aimed to investigate the refractive error in Hong Kong preschool children and its association with near work (including digital device usage) among these children.Methods : A total of 336 preschool children aged between 3 and 7 years from 6 local kindergartens were examined. (edu.hk)
  • Out of the affected subjects there were more number of uncorrected ammetropic children though the magnitude of refractive state was less when compared with urban population. (biomedjournal.com)
  • Childhood visual impairment due to refractive error is a significant problem among school children and has a considerable impact on public health. (biomedjournal.com)
  • 2007). This study was designed to evaluate the refractive state in school going children of rural and urban background. (biomedjournal.com)
  • The Refractive Error Among Children (REACH) project aims to reduce visual impairment due to uncorrected refractive error among school-going children and provide a sustainable and scalable solution to a shortage of care. (orbis.org)
  • Visual impairment and refractive error in school children in Bhutan: The findings from the Bhutan School Sight Survey (BSSS 2019). (bvsalud.org)
  • To estimate the nationwide prevalence of visual impairment and associated refractive error in school children in Bhutan . (bvsalud.org)
  • We screened 671 119 children (56.7% males) for significant refractive error and other eye ailments. (who.int)
  • We quantified the interrelationship between retinal blood vessel (BV) anatomical variation, spherical equivalent (SE) of refractive error, and functional diagnostic parameters in glaucoma to identify optimal parameters for the improvement of optical coherence tomography (OCT) retinal nerve fiber layer thickness (RNFLT) norms. (arvojournals.org)
  • One parameter readily available to clinicians, which represents the anatomical variations related to axial ametropia and is supposed to have a strong impact on individual RNF bundles, is spherical equivalent (SE) of refractive error. (arvojournals.org)
  • Refractive error, expressed as spherical equivalent power (SE), and axial length (AL) were the main outcome measures. (edu.hk)
  • By controlling the irradiation dose and spatial irradiance profile, the refractive power of the light-adjustable IOL is modified to add or subtract spherical power, or to eliminate astigmatic error. (medscape.com)
  • The number of people globally with refractive errors has been estimated at one to two billion. (wikipedia.org)
  • What are the types of refractive errors? (eyecraftersny.com)
  • However, some may have very unequal eyes, with refractive error in one eye only, refractive error in both eyes but much stronger in one, or even different types of refractive error in each eye. (pedopnj.com)
  • There are four primary types of refractive errors. (kyeye.com)
  • When it comes to refractive errors, three types tend to be the most prevalent. (kyeye.com)
  • RÉSUMÉ Le diagnostic et la prise en charge précoces d'un strabisme sont nécessaires pour éviter les complications telles qu'une amblyopie. (who.int)
  • 3 , 14-16 The purpose of this work is to find out if there is any correlation between corneal parameters (namely, central corneal thickness and corneal power) and the refractive error in the myopic adult Egyptian population. (dovepress.com)
  • Refractive errors are caused by a range of eye disorders. (booksbetween.com)
  • Refractive errors are eye disorders caused by irregularity in the shape of the eye. (sightsavers.org)
  • The World Health Organization estimates that 153 million people worldwide live with visual impairment due to uncorrected refractive errors. (health.mil)
  • Uncorrected refractive defects can cause headaches, especially following visual tasks. (savesightcentre.com)
  • Correspondence between visual acuity, refractive error, and the speed of visual perception. (bvsalud.org)
  • Other terminology include anisometropia, when the two eyes have unequal refractive power, and aniseikonia which is when the magnification power between the eyes differ. (wikipedia.org)
  • More than 150 million Americans use corrective eyewear to compensate for refractive errors, spending over $15 billion annually . (kyeye.com)
  • Visiting an optometrist for regular eye exams is crucial to detect these errors early and discuss suitable corrective measures. (kyeye.com)
  • The refractive error is the discrepancy between the eye's optical power and its length that causes light to be misdirected. (kyeye.com)
  • Their effectiveness is well characterized, and an optometrist performing a subjective refraction frequently uses one to estimate errors before refinement. (arvojournals.org)