Refractive errors. Medical search

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.

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.

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.

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.

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.

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)

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 ...

https://en.wikipedia.org/wiki/Refractive_error

... 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 ...

https://en.wikipedia.org/wiki/Refractive_surgery

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.). ...

https://en.wikipedia.org/wiki/Far-sightedness

"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 ...

https://en.wikipedia.org/wiki/Prevention_of_Blindness_Trust

... 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 ...

https://en.wikipedia.org/wiki/Focometer

Weale RA (2003). "Epidemiology of refractive errors and presbyopia". Survey of Ophthalmology. 48 (5): 515-43. doi:10.1016/S0039 ... Accumulation of errors: The idea that ageing results from chance events that escape proof reading mechanisms, which gradually ... as each cell division is a chance for errors in DNA replication. Genetic instability: Dogs annually lose approximately 3.3% of ...

https://en.wikipedia.org/wiki/Ageing

In the case of the eye, a large pupil emphasizes refractive error and a small pupil masks it. This phenomenon can cause a ... Other types of refractive error are hyperopia, astigmatism, and presbyopia. Various forms of myopia have been described by ... 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. ...

https://en.wikipedia.org/wiki/Myopia

Honavar SG (2019). "The burden of uncorrected refractive error". Indian J Ophthalmol. 67 (5): 577-578. doi:10.4103/ijo.IJO_762_ ...

https://en.wikipedia.org/wiki/Santosh_G._Honavar

"Myopia and Refractive errors in Dogs" (PDF). Investigative Optholmology and 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 ...

https://en.wikipedia.org/wiki/Myopia_in_animals

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 ...

https://en.wikipedia.org/wiki/Contact_lens

... 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 ...

https://en.wikipedia.org/wiki/Astigmatism

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 ...

https://en.wikipedia.org/wiki/Pinhole_occluder

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. ...

https://en.wikipedia.org/wiki/Bates_method

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. ...

https://en.wikipedia.org/wiki/Red_reflex

Causes include: Refractive errors Divergence insufficiency Convergence excess; this can be due to nerve, muscle, congenital or ...

https://en.wikipedia.org/wiki/Esophoria

Does cryotherapy affect refractive error? Ophthalmology 108:343-347, 2001. Bleyl SB, Kivlin JD, et al. (2007). "Brachymesomelic ...

https://en.wikipedia.org/wiki/Jane_D._Kivlin

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. ...

https://en.wikipedia.org/wiki/Eye_chart

Goyal, Ashish; Bopardikar, Ajit; Tiwari, Vijay Narayan (2018). "Estimation of Spherical Refractive Errors Using Virtual Reality ...

https://en.wikipedia.org/wiki/Near_point

Refractive errors in patients with FXS are also common. Individuals with FXS are at a higher risk of developing seizures, with ...

https://en.wikipedia.org/wiki/Fragile_X_syndrome

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 ...

https://en.wikipedia.org/wiki/Corrective_lens

"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 ...

https://en.wikipedia.org/wiki/Brien_Holden_Vision_Institute

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 ...

https://en.wikipedia.org/wiki/Photorefractive_keratectomy

"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, ...

https://en.wikipedia.org/wiki/Excimer_laser

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 ...

https://en.wikipedia.org/wiki/Amar_Agarwal

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., ...

https://en.wikipedia.org/wiki/Scleral_reinforcement_surgery

Astigmatism is a condition wherein there occurs significant refractive error. Moreover, ocular albino eyes become crossed, a ...

https://en.wikipedia.org/wiki/Ocular_albinism_type_1

For an unaccommodated myopic eye, the far point is closer than 6 m. It depends upon the refractive error of the person's eye. ...

https://en.wikipedia.org/wiki/Far_point

Amblyopia: is a category of vision loss or visual impairment that is caused by factors unrelated to refractive errors or ... The most common causes of visual impairment globally in 2010 were: Refractive error (42%) Cataract (33%) Glaucoma (2%) Age- ... The most common causes of visual impairment globally are uncorrected refractive errors (43%), cataracts (33%), and glaucoma (2 ... This includes cataracts, onchocerciasis, trachoma, glaucoma, diabetic retinopathy, uncorrected refractive errors, and some ...

https://en.wikipedia.org/wiki/Visual_impairment

In an eye exam, the term refraction is the determination of the ideal correction of refractive error. Refractive error is an ... Examples of refractive error are myopia, hyperopia, presbyopia and astigmatism. The errors are specified in diopters, in a ... The information bounced back to the instrument gives an objective measurement of refractive error without asking the patients ... Based on the movement and orientation of this retinal reflection, the refractive state of the eye is measured. An auto- ...

https://en.wikipedia.org/wiki/Eye_examination

... the device provides a quantitative measurement of the refractive error without the need of a physician on the ground. The test ... NETRA allows for the early, low-cost diagnosis of the most common refractive Refractive Disorders. The subject looks into the ... Interactive Display for Estimating Refractive Errors and Focal Range" (PDF). ACM Transactions on Graphics. 29 (4). doi:10.1145/ ... eye diagnostics like NETRA is tremendous and is global in scale-over half a billion people have uncorrected refractive errors. ...

https://en.wikipedia.org/wiki/MIT_NETRA

... errors) between desired and calculated properties; Reduction of the sum of square errors using the Solver option in Microsoft ... Glass batch calculation Calculation of the Refractive Index of Glasses Vogel, Werner (1994). Glass chemistry (2nd revised ed ... Systematic errors such as seen in the picture are quantified by dummy variables. Further details and examples are available in ... ISBN 1-57498-225-7. The Mixed-Alkali Effect for the Viscosity of Glasses Overview, Measurement Errors of Glass Properties ...

https://en.wikipedia.org/wiki/Calculation_of_glass_properties

They compensate for refractive errors (such as presbyopia) by providing variable focusing, allowing users to adjust them for ... The appropriate addition range depends on the user's level of refractive error.[clarification needed] A tiny mechanism, ...

https://en.wikipedia.org/wiki/Adjustable-focus_eyeglasses

... no error or ambiguity will result. Whichever convention is used, it will always be understood that Pr can never exceed Pi . In ... a loss that takes place at discontinuities of refractive index, especially at an air-glass interface such as a fiber endface. ...

https://en.wikipedia.org/wiki/Return_loss

K.L. Bai, J. Katz, On the refractive index of sodium iodide solutions for index matching in PIV, Exp. Fluids 55(4) (2014). S. ... J. Chen, J. Katz, Elimination of peak-locking error in PIV analysis using the correlation mapping method, Measurement Science ... Unobstructed particle image velocimetry measurements within an axial turbo-pump using liquid and blades with matched refractive ...

https://en.wikipedia.org/wiki/Joseph_Katz_(professor)

Because pressure-measurement error can be caused by more than just CCT (such as by corneal hydration or elastic properties), it ... Journal of Cataract and Refractive Surgery. 40 (8): 1301-1306. doi:10.1016/j.jcrs.2014.01.032. PMID 24943904. "Xen Gel Stent". ... Journal of Cataract and Refractive Surgery. 34 (3): 433-440. doi:10.1016/j.jcrs.2007.11.029. PMID 18299068. S2CID 23904366. ... Journal of Cataract and Refractive Surgery. 33 (7): 1217-1226. doi:10.1016/j.jcrs.2007.03.051. PMID 17586378. S2CID 36397585. ...

https://en.wikipedia.org/wiki/Glaucoma

Prenatal stage Premature Birth Refractive error Congenital cataract Retinopathy of prematurity (ROP) Infection such as ...

https://en.wikipedia.org/wiki/Congenital_blindness

A negative refractive index in the optical range was first demonstrated in 2005 by Shalaev et al. (at the telecom wavelength λ ... Wikipedia articles incorporating text from the National Institute of Standards and Technology, CS1 errors: missing periodical, ... PMMs can be made with a gradient index (a material whose refractive index varies progressively across the length or area of the ...

https://en.wikipedia.org/wiki/Plasmonic_metamaterial

As solutes other than sucrose may affect the refractive index and the specific gravity differently, this refractive "Brix" ... and the Normal-Eichungs Kommission to 6 with the goal of the Commission being to correct errors in the 5th and 6th decimal ... in particular its refractive index and the extent to which it rotates the plane of linearly polarized light. The refractive ... which is based on knowledge of the way the refractive index of sucrose changes. For example, the refractive index of a sucrose ...

https://en.wikipedia.org/wiki/Brix

... refractive errors,congenital color deficiency and various risk factors that are associated with the conditions https://pubmed. ... Cite error: A tag is missing the closing (see the help page). A new recording of fourteen Rachmaninov songs, a selection of ... Pages with reference errors, Pages with incorrect ref formatting, Articles with topics of unclear notability from September ...

https://en.wikipedia.org/wiki/Yoram_Chaiter

Each used a f/7.9 refractive optical system with a focal length of 150 mm. A frame-transfer charge-coupled device (CCD), a ... The root cause of the event was reported to be a software programming error. To cruise from Earth to its targets, Dawn traveled ... It responded by going into safe mode and sending a signal to engineers, who fixed the error on July 2, 2015. Engineers ...

https://en.wikipedia.org/wiki/Dawn_(spacecraft)

... s convert a prescription for the correction of a refractive error into an ophthalmic lens or some other device, such as ... since even tiny errors cause eye strain. Pupilometer apps have also been developed for smart phones and tablets. The fitting ...

https://en.wikipedia.org/wiki/Optician

First of all, the measurement of refractive error may vary from one measurement to the next. Secondly, different criteria have ... Anisometropia is caused by common refractive errors, such as astigmatism, far-sightedness, and myopia, in one eye. ... a condition where even when correcting the refractive error properly, the person's vision in the affected eye is still not ... refraction and refractive errors: control of postnatal eye growth, current and developing treatments", Pediatric Ophthalmology ...

https://en.wikipedia.org/wiki/Anisometropia

Later analyses showed several errors and incorrect assumptions with this experiment but, serendipitously, these errors canceled ... Lipid bilayers exhibit high levels of birefringence where the refractive index in the plane of the bilayer differs from that ... perpendicular by as much as 0.1 refractive index units. This has been used to characterise the degree of order and disruption ...

https://en.wikipedia.org/wiki/Lipid_bilayer

... it is susceptible to error. In practice, the error can be as high as 25 percent. The color indicator tubes are well suited for ... A silicon oxide sensor can be an optical device that changes its refractive index as water is absorbed into the sensitive layer ...

https://en.wikipedia.org/wiki/Moisture_analysis

Determination of refractive index ISO 281:2007 Rolling bearings - Dynamic load ratings and rating life ISO 282:1992 Conveyor ... Balance errors [Withdrawn: replaced with ISO 21940-14] ISO/R 1941:1970 Flat seal for hydraulic couplings [Withdrawn without ... Determination of the refractive index of the fat (Reference method) ISO 1740:2004 Milkfat products and butter - Determination ... Determination of refractive index ISO 490:1993 Cinematography - Magnetic stripes and magnetic recording head gaps for sound ...

https://en.wikipedia.org/wiki/List_of_International_Organization_for_Standardization_standards,_1–1999

... error free, detection could be obtained. This is done by compressing all energy into an infinitesimal time slice. What limits ... radar beam follows a linear path in vacuum but follows a somewhat curved path in atmosphere due to variation in the refractive ...

https://en.wikipedia.org/wiki/Radar

... diabetes heart disease hypertension inflammatory bowel disease intellectual disability mood disorder obesity refractive error ... Most congenital metabolic disorders known as inborn errors of metabolism result from single-gene defects. Many such single-gene ... Genetic epidemiology List of genetic disorders Population groups in biomedicine Mendelian error "Genetic Disorders". Learn. ...

https://en.wikipedia.org/wiki/Genetic_disorder

He realised that even if light were transmitted as waves the refractive index of the glass-air interface should have varied as ... 125-35; also translated (with several errors) by R.R. Traill as "Letter from Augustin Fresnel to François Arago concerning the ... These predictions arose because the refractive index of a substance such as glass depends on the ratio of the velocities of ... In 1810, François Arago realised that variations in the refractive index of a substance predicted by the corpuscular theory ...

https://en.wikipedia.org/wiki/Aether_drag_hypothesis

... and refractive visual errors. The nose may be small, wide, and upturned. The development of the ears and auditory system may be ...

https://en.wikipedia.org/wiki/Noonan_syndrome

ISBN 0-683-30076-8. {{cite book}}: ,author= has generic name (help) v t e v t e (CS1 errors: generic name, Articles with short ... In ophthalmoscopic examination it appears as small, flat, yellow, highly refractive crystals of cholesterol floating freely in ...

https://en.wikipedia.org/wiki/Synchysis_scintillans

There are many causes of blurred vision: Refractive errors: Uncorrected refractive errors like myopia, high hypermetropia, and ... visual blur due to refractive errors can be corrected to normal using corrective lenses or refractive surgeries. Presbyopia due ... ISBN 978-81-312-1132-8. "WHO , Global magnitude of visual impairment caused by uncorrected refractive errors in 2004". WHO. ... Other medical conditions may include refractive errors such as myopia, high hypermetropia, and astigmatism, amblyopia, ...

https://en.wikipedia.org/wiki/Blurred_vision

If we leave the width L fixed in each point, but we change the value of the refractive index n ( x ) {\displaystyle n(x)} we ... In 1991, a Bell Labs research team transmitted solitons error-free at 2.5 gigabits over more than 14,000 kilometres, using ... Now let us assume we have a medium that shows only nonlinear Kerr effect but its refractive index does not depend on frequency ... It is because generated impulses have a non-zero bandwidth and the medium they are propagating through has a refractive index ...

https://en.wikipedia.org/wiki/Soliton_(optics)

CS1 errors: missing periodical, CS1 errors: generic name, CS1 maint: DOI inactive as of September 2022, CS1 maint: multiple ... It has one of the lowest refractive indexes and the furthest transmission range in the deep UV of most common materials. Finely ... names: authors list, CS1 maint: uses authors parameter, CS1: long volume value, CS1 errors: missing title, CS1 errors: bare URL ...

https://en.wikipedia.org/wiki/Lithium

The errors in these approximations, which were obtained empirically, are of order h 3 {\displaystyle h^{3}} and h 5 , {\ ... In a material that is optically anisotropic (birefringent), the refractive index depends on the direction of the light. The ...

https://en.wikipedia.org/wiki/Ellipse

If the shape of the cornea is fairly regular and refractive error is similar to that of the other eye, it is usually possible ... A few months after the stitches are removed, measurements are made of the shape of the cornea and refractive error. ... to fix any error with glasses; if not, a hard lens may be necessary to correct vision. One of the largest causes for issue in ...

https://en.wikipedia.org/wiki/Corneal_button

Refractive and reflective optical properties can be tabulated as a function of wavelength, to approximate system performances; ... By superimposing a reference beam with the beam reflected from the surface to be measured, error maps, known as interferograms ... tolerances and errors can also be evaluated. In addition to focal integrity, aspheric lens systems can be tested for ... form of asphere surface form deviation slope error centre thickness roughness A distinction is made between tactile, i.e. ...

https://en.wikipedia.org/wiki/Aspheric_lens

This is due in large part to advances in optometry which allow for better measurement of refractive error, so that glasses and ...

https://en.wikipedia.org/wiki/Monocle

The refractive index of ice Ih is 1.31. The accepted crystal structure of ordinary ice was first proposed by Linus Pauling in ... CS1 errors: missing periodical, CS1 maint: multiple names: authors list, Articles with short description, Short description is ...

https://en.wikipedia.org/wiki/Ice_Ih

Here considering only refractive caustic, the objective can be determined as follows (similar principle for reflective caustic ... mean square error of the rendered image and the target c: contains elements which can influence the generated image I: target ... Common refractive materials: acrylic, polycarbonate, polyethylene, glass, diamond Common reflective materials: steel, iron, ...

https://en.wikipedia.org/wiki/Caustic_(optics)

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 ... Article: Prevalence of refractive error in Portugal estimated from ophthalmic lens manufacturing... ...

https://medlineplus.gov/refractiveerrors.html

Prevalence of refractive error and low vision among schoolchildren in Cairo El Bayoumy, B.M.; Saad, A.; Choudhury, A.H. (‎ ... A preliminary survey was conducted to detect the prevalence of refractive error [‎RE]‎ and low vision among 5839 schoolchildren ... This study evaluated the preventable environmental risk factors of refractive error [‎RE]‎ among 1292 Egyptian schoolchildren ... Browsing EMRO Journal Articles (‎EMHJ)‎ by Subject "Refractive Errors". 0-9. A. B. C. D. E. F. G. H. I. J. K. L. M. N. O. P. Q ...

https://apps.who.int/iris/handle/10665/115916/browse?authority=Refractive+Errors&type=mesh

Refractive errors are some of the most common vision problems people experience. ... A refractive error is something about the natural shape of your eyes that makes your vision blurry. ... Many refractive errors first appear in kids. But you can develop a refractive error at any point in your life, even if youve ... What causes refractive errors?. Changes in the shape of your cornea, your lens or your whole eye can cause refractive errors. ...

https://my.clevelandclinic.org/health/diseases/24224-refractive-errors

Prevalence of refractive error and low vision among schoolchildren in Cairo El Bayoumy, B.M.; Saad, A.; Choudhury, A.H. (‎ ... Elimination of avoidable visual disability due to refractive errors : report of an informal planning meeting, Geneva, 3-5 July ... A preliminary survey was conducted to detect the prevalence of refractive error [‎RE]‎ and low vision among 5839 schoolchildren ... This study evaluated the preventable environmental risk factors of refractive error [‎RE]‎ among 1292 Egyptian schoolchildren ...

https://extranet.who.int/iris/restricted/browse?authority=Refractive+Errors&type=mesh

... had their refractive error corrected with contact lenses where the mean refractive error measured -3.12D. Each participant was ... The refractive error was measured using cycloplegic autorefraction over a two year period. A causative link between peripheral ... Visual acuity results improved in both treatment groups (P,0.05); the control group was unchanged for VA and refractive error. ... Rosen RC, Schiffman HR, Meyers H. Behavioral treatment of myopia: refractive error and acuity changes in relation to axial ...

https://www.aao.org/complimentary-therapy-assessment/visual-training-refractive-errors-cta--october-200

Diabetic macular edema patients have minimal changes in refractive error. The correction of refractive error may be considered ... REFRACTIVE ERROR CHANGE DURING TREATMENT OF DIABETIC MACULAR EDEMA. A Post Hoc Analysis of the Diabetic Retinopathy Clinical ... REFRACTIVE ERROR CHANGE DURING TREATMENT OF DIABETIC MACULAR EDEMA: A Post Hoc Analysis of the Diabetic Retinopathy Clinical ... REFRACTIVE ERROR CHANGE DURING TREATMENT OF DIABETIC MACULAR EDEMA: A Post Hoc Analysis of the Diabetic Retinopathy Clinical ...

https://journals.lww.com/retinajournal/Abstract/2022/11000/REFRACTIVE_ERROR_CHANGE_DURING_TREATMENT_OF.6.aspx

Refractive error that is not diagnosed or treated is called uncorrected refractive error (URE). Uncorrected refractive error is ... Table 1. Uncorrected Refractive Error Prevalence Sources.. Uncorrected Refractive Error Prevalence Sources. Author. Date of ... Overall Refractive Error Prevalence Rates. Figure 1 below shows estimated prevalence rates for uncorrected refractive error ( ... The Prevalence and Risk Indicators of Uncorrected Refractive Error and Unmet Refractive Need in Latinos: the Los Angeles Latino ...

https://www.cdc.gov/visionhealth/vehss/data/studies/uncorrected-refractive-error.html

... are caused when the shape of the eye, length of the eyeball or similar issues do not allow light to focus ... World Health Organization: Blindness and vision impairment: Refractive errors * American Academy of Ophthalmology: Refractive ... Anyone can have refractive errors, but youre at higher risk if you have family members who wear glasses or contact lenses. ... Most types of refractive errors, like nearsightedness, usually start in childhood. Presbyopia is common in adults ages 45 and ...

https://www.seeintl.org/refractive-errors/

Refractive errors and school performance in Brazzaville, Congo * P.W. Atipo-Tsiba ... Conclusion: Refractive errors largely determines pupil performance in schools in Brazzaville, Congo. The routine use of glasses ... Objective: To determine the role of refractive errors in school performance in Brazzaville. ...

https://www.ajol.info/index.php/eamj/article/view/145613

The Regional Planning Course on Refractive Errors and Low Vision will be conducted from 19-25 November 2007 in the Regional ... Course on Refractive Errors and Low Vision will be held in the WHO ... Correcting refractive errors is so simple; however it has yet received little government or NGOs attention and has been easily ... Media centre , News , Press archive , 2007 , Course on Refractive Errors and Low Vision will be held in the WHO ...

https://www.emro.who.int/press-releases/2007/course-on-refractive-errors-and-low-vision-will-be-held-in-the-who.html

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 ...

https://bjo.bmj.com/content/97/6/765

... this is possibly a refractive error in your eyes. Refractive errors are surprisingly common, affecting a considerable amount of ... Refractive errors of the eye. Posted on March 9, 2020. May 13, 2021. by Dr. Chukwudi Ekomaru , 2 min read ... A refractive error is an eye disorder which results in the inability of the eye to clearly focus on objects, resulting in ... In individuals without refractive errors, the lens is elastic and alters its shape to increase its power, bringing visible ...

https://3d4medical.com/es/blog/refractive-errors-of-the-eye

653T,653Z,Apel,astigmatism,enhancement,Gatzioufas,McKelvie,McLintock,piggyback,pseudophakic,refractive,refractive error, ... Home , Eye Science , Outcomes of toric supplementary intraocular lenses for residual astigmatic refractive error in ... Outcomes of toric supplementary intraocular lenses for residual astigmatic refractive error in pseudophakic eyes. Posted on 1/ ...

https://rayner.com/eye_science/outcomes-of-toric-supplementary-intraocular-lenses-for-residual-astigmatic-refractive-error-in-pseudophakic-eyes/

Refractive errors, including myopia, are the most frequent eye disorders worldwide and an increasingly common cause of ... Our results support the notion that refractive errors are caused by a light-dependent retina-to-sclera signaling cascade and ... Genome-wide association meta-analysis highlights light-induced signaling as a driver for refractive error. Publication. ... Genome-wide association meta-analysis highlights light-induced signaling as a driver for refractive error. Nature Genetics, 1- ...

https://repub.eur.nl/pub/107321

... for diagnosing refractive errors in children. Methods 123 school-age children (9.9 ± 3.3 years) with moderate refractive error ... were used to evaluate the performance of the device in measuring refractive error. Results The spherical equivalent refraction ...

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0240933

... clearly indicated that detailed comparisons of refractive error prevalence across study reports are generally not possible ... Case finding for refractive errors: assessment of refractive error and visual impairment in children. Leon B Ellwein PhD. ... Refractive error in this age group was usually due to myopia with a relatively high prevalence among Chinese children (Figure 3 ... Refractive error study in children: sampling and measurement methods for a multi-country survey. Am J Ophthalmol 2000; 129: 421 ...

https://www.cehjournal.org/article/case-finding-for-refractive-errors-assessment-of-refractive-error-and-visual-impairment-in-children/

Internal Compensation of Lateral Coma Aberration: Relationship to Refractive Error You will receive an email whenever this ... N.J. Coletta, H. Han, A. Moskowitz; Internal Compensation of Lateral Coma Aberration: Relationship to Refractive Error . Invest ... We examined the roles of pupil displacement and refractive error in the amount of corneal and ocular lateral coma aberration. ... values were smaller than the corneal values and did not vary significantly with either pupil displacement or refractive error. ...

https://iovs.arvojournals.org/article.aspx?articleid=2391367

Refractive errors are extremely common and they affect the ability of the eyes to focus light properly on the retina, at the ... What are refractive errors? Refractive errors are extremely common and they affect the ability of the eyes to focus light ... A refractive error can cause a number of symptoms. Some of them are harder to identify, especially when the refractive error ... Genetics can play a huge role when it comes to refractive errors. If you have family members who have refractive errors, you ...

https://www.visionenhancers.com/blogs/about-eye-conditions/knowing-about-and-dealing-with-refractive-errors

"Refractive Errors" by people in this website by year, and whether "Refractive Errors" was a major or minor topic of these ... "Refractive Errors" is a descriptor in the National Library of Medicines controlled vocabulary thesaurus, MeSH (Medical Subject ... Unequal refractive error and high astigmatism associated with orbital lymphangioma. Mil Med. 1993 Jun; 158(6):429-31. ... Below are the most recent publications written about "Refractive Errors" by people in Profiles. ...

https://profiles.ucdenver.edu/display/205127

Prevalence rates of refractive errors in Sumatra, Indonesia. Authors: Saw, S.-M. Gazzard, G.. Koh, D. Farook, M.. Widjaja, D.. ... Saw, S.-M.,Gazzard, G.,Koh, D.,Farook, M.,Widjaja, D.,Lee, J.,Tan, D.T.H. (2002-10). Prevalence rates of refractive errors in ... Refractive error measurements were obtained with one of two handheld autorefractors. Household interviews were conducted to ... The prevalence rate of high myopia is lower than in most other populations, and other refractive errors are common. ...

https://scholarbank.nus.edu.sg/handle/10635/113607

CRT outdoors Pathology and eye health Pharmaceuticals Pre-Myope Progressive Lenses Refraction refractive error Risk factors ...

https://www.myopiaprofile.com/tag/refractive-error/

Tag: refractive error. Visual Disabilities and Impairment: Mostly Refractive, Mostly Preventable. by DrB • July 31, 2017. • 0 ...

https://drboulet.com/tag/refractive-error/

... by addressing Uncorrected Refractive Error (URE) in Mozambique and the wider region of sub-Saharan Africa by providing ... The cost of refractive services must be addressed if the burden of URE is to be reduced. While the average WTP value lies ... The average amount in USD participants would be willing to pay for refractive services was US$12 for stated choice and US$15 ... Thompson, S. J. (2014).The Social and Economic Impact of Refractive Error in Mozambique.Doctoral Thesis.Technological ...

https://arrow.tudublin.ie/sciendoc/178/

The refractive errors of the students eyes were measured using non-cycloplegic autorefraction. ... Prevalence of refractive conditions in Singapore teenagers. Grade 9 and 10 students (n = 946) aged 15-19 years from two ...

https://onesight.essilorluxottica.com/research/prevalence-of-refractive-errors-in-teenage-high-school-students-in-singapore

... PubMed, SCI, Scopus, ESCI, ... This is how NGOs, instead of States, are called upon to assume the leading role in the management of refractive errors at the ... Background: Uncorrected refractive errors (URE) are a serious public health problem by their magnitude, the multiple ... McCarty CA, "Uncorrected refractive error," British Journal of Ophthalmology, vol. 90, no. 5. BMJ Publishing Group 90 (2006). ...

https://www.fortunejournals.com/articles/situation-analysis-of-uncorrected-refractive-errors-in-subsaharan-francophone-african-countries.html

Visual Function After Correction of Distance Refractive Error with Ready-Made and Custom Spectacles: A Randomized Clinical ...

https://onesight.essilorluxottica.com/research/visual-function-after-correction-of-distance-refractive-error-with-ready-made-and-custom-spectaclespercent3a-a-randomized-clinical-trial

HONG, CHEN AI (2000) Effect of the body posture on visual acuity, refractive error and binocular vision. UNSPECIFIED. ... Effect of the body posture on visual acuity, refractive error and binocular vision. ...

https://oarr.uitm.edu.my/id/eprint/11751/

There are several types of refractive surgeries, but the most popular are:. *Refractive lensectomy, also called refractive lens ... Refractive Errors (Vision Problems). Overview. We must have light in order to see. Most common vision problems are caused by ... Your eye doctor will determine the type and degree of refractive error you have by performing a test called refraction. This ... Eyeglasses are the simplest and safest way to correct refractive errors. Eyeglass lenses are designed with precise curves to ...

https://scoallentown.com/condition/refractive-errors-vision-problems

The shape of your cornea is responsible for the majority of your eyes refractive power. ... it is usually because there is a refractive error present. Any eye with a refractive error is considered to be ametropic. ... Common refractive errors. Your ability to refract light correctly depends on four key characteristics that can often change ... Laser Eye Surgery can correct refractive errors by removing a pre-determined amount of cells from the cornea, which is located ...

https://www.optilase.com/news/what-causes-refractive-errors/

AIM: To study the distribution of refractive error in different ethnic groups of Nepal. METHODS: A total of 1276 new eye ... Karki KJ, Karki M. Refractive error profile--a clinical study. Kathmandu University Medical Journal. 2004 Jul-Sep; 2(3): 208-12 ... The ethnic distribution of refractive error shows that there are 32.44% Newars; 27.50% Brahmins; 21.63% Chhetriyas; 12.14% ... CONCLUSION: Thus, a refractive error profile is drawn up in Nepalese population. ...

https://imsear.searo.who.int/handle/123456789/46452?locale=es

There are four different types of refractive error (RE): myopia, hyperopia, astigmatism, and presbyopia. (cdc.gov)
Refractive errors, including myopia, are the most frequent eye disorders worldwide and an increasingly common cause of blindness. (eur.nl)
Refractive error in this age group was usually due to myopia with a relatively high prevalence among Chinese children (Figure 3). (cehjournal.org)
The prevalence rate of high myopia is lower than in most other populations, and other refractive errors are common. (nus.edu.sg)
Astigmatism may occur with other refractive errors such as myopia (nearsightedness) and hyperopia (farsightedness). (yeagervisioncare.com)
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)
Myopia (nearsightedness), hyperopia (farsightedness), presbyopia , and astigmatism are just some samples of refractive errors. (filmannex.com)
Lasers can be used to carefully reshape the cornea of the eye - the transparent front part of the eye that covers the iris, pupil, and anterior chamber - to correct refractive errors that cause conditions like short-sightedness (myopia), long-sightedness (presbyopia), or blurred vision (astigmatism). (zmescience.com)
A 2015 report of the joint World Health Organization and Brien Holden Vision Institute Global Scientific Meeting on Myopia defines myopia as the presence of ocular refractive error of ≤ -0.50 diopter and high myopia as the presence of ocular refractive error of ≤ -5.00 diopter. (medscape.com)
Significant Refractive Errors Severe myopia (greater than or equal to -6 D), severe hyperopia (greater than or equal to +5.25 D), or prior LVC (LASIK, SMILE or PRK) that corrected for the aforementioned refractive error, excluding those with an AREDS grade of 1 to 4 or a LOCS III grade of 2 to 6. (who.int)
Refractive defects include myopia, hypermetropia, and astigmatism which generally occurs due to refractive errors leading to vision defects. (eyeqindia.com)
They are used to compensate mild refractive errors in patients with myopia , hyperopia and astigmatism . (icrcat.com)
Refractive errors such as myopia, hyperopia, and astigmatism are currently the most common eye problems. (koalaeye.com)
Myopia, also known as nearsightedness, is a common type of refractive error where close objects appear clear, but distant objects appear blurry. (nvisioncenters.com)
Children benefit from wearing contact lenses more than just having refractive error correction and myopia control, they have a better self-esteem and improved quality of life. (bsz-bw.de)
Myopia is a refractive error that happens when the eye focuses incoming light in front of the retina, rather than directly on it, resulting in blurred distance vision. (astoria-vision.com)

Depending on which type of refractive error you have, something about the shape of your eyeball, your cornea or your lens prevents your eyes from focusing correctly on objects you're looking at. (clevelandclinic.org)
Changes in the shape of your cornea, your lens or your whole eye can cause refractive errors. (clevelandclinic.org)
Refractive disorders are usually the result of an eyeball that is too short or too long, a cornea (the clear front part of your eye) that is irregularly shaped or a lens that is curved too much or too little. (scoallentown.com)
Refractive surgery permanently changes the shape of the cornea. (scoallentown.com)
PRK refractive uses a laser to reshape the surface layer of your cornea to correct the focus of light rays on your retina. (scoallentown.com)
Laser Eye Surgery can correct refractive errors by removing a pre-determined amount of cells from the cornea, which is located at the front of the eye and is responsible for the majority of your eye's refractive power. (optilase.com)
The cornea is designed to work with light passing from the air, which has a refractive index of 1.00. (optilase.com)
If the eye doesn't have enough refractive power because it is too short or the surface of the cornea is too flat, light lands beyond the retina to create a distorted image. (optilase.com)
For some people, a problem with the shape of the cornea (the eye's transparent outer layer) causes refractive errors. (oculase.com)
Some types of surgery, like laser eye surgery, change the shape of your cornea to fix refractive errors. (oculase.com)
By specifically removing tissue from different portions of the cornea, the surgeon is able to correct the different refractive errors. (shraddhaeyehospital.com)
Another method for correcting astigmatism is by changing the shape of the cornea through refractive or laser eye surgery. (yeagervisioncare.com)
Refractive errors happen when there is a change in length of the eyeball, a change in the shape of the cornea, or as a result of an aging lens. (arlingtoneyecenter.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)
If the cornea or lens is not perfectly round or smooth, an error may occur in the refraction of light as it will cause the light to bend unnaturally causing blurry vision. (filmannex.com)
Dr David Gunn is a Cornea, Cataract and Refractive Surgeon based in Brisbane. (optometryqldnt.org.au)
Dr Gunn specialises in medical and surgical diseases of the cornea, routine and complex cataract surgery and laser and refractive eye surgery. (optometryqldnt.org.au)
A lens is a simple medical device to correct focal power and, refractive errors occurring in the cornea of an eye. (toppr.com)
Contact lenses may be recommended as they can sometimes improve the acuities of some students with irregular cornea surfaces or with high refractive errors. (teachingvisuallyimpaired.com)

Unequal refractive error and high astigmatism associated with orbital lymphangioma. (ucdenver.edu)
Astigmatism can be corrected with glasses, contacts or with refractive surgery. (scoallentown.com)
ASTIGMATISM (cylindrical error) occurs when incoming light rays unable to reach a common focus within the eye. (shraddhaeyehospital.com)
Preoperative measurements seem to be the main source of error for our toric intraocular lens (t-IOL) calculations,' confessed Dr Nino D. Hirnschall [VIROS (Vienna Institute for Research in Ocular Surgery), Hanusch Hospital, Vienna, Austria] during the 'Assessment of Astigmatism' session, which took place on the first day of this year's ESCRS meeting. (ophthalmologytimes.com)
Of course, you don't actually know what that error is, but we used a difference vector between the keratometry and the topography and then we used a regression model to predict the remianing astigmatism after surgery. (ophthalmologytimes.com)
Eyeglasses and contact lenses are valuable vision aids that allow people with refractive errors such as nearsightedness, farsightedness, astigmatism, etc. to see clearly and comfortably. (eyewa.com)

Most types of refractive errors, like nearsightedness, usually start in childhood. (seeintl.org)
Almost all cases of nearsightedness can be corrected with a concave lens or with one of several types of refractive surgery. (scoallentown.com)
Refractive lensectomy, also called refractive lens exchange, corrects nearsightedness or farsightedness. (scoallentown.com)

Talk to your eye care specialist about vision correction surgery if you have a refractive error but don't want to wear corrective lenses. (clevelandclinic.org)
Uncorrected refractive error is often defined as presenting visual acuity (VA) of 20/50 or worse, and best corrected VA of 20/40 or better, indicating that normal acuity may be achieved through refraction correction. (cdc.gov)
The prevalence of visual impairment with best refractive correction represents the degree of vision loss attributable to causes other than refractive error. (cehjournal.org)
The use of the EXCIMER LASER in corneal refractive surgery has greatly increased the safety of the procedure as the refractive correction is achieved by the removal of a little as 10 to 20% of the total corneal thickness. (shraddhaeyehospital.com)
An eye vision correction surgery is required in case you need a permanent solution against the refractive errors. (vostochnyde.info)
Children who need vision correction because of refractive errors should have annual eye exams throughout their school years to evaluate any changes. (allaboutvision.com)
An excess of false positives can overload referral sites, lead to unnecessary expenditure by patients and reduce confidence in the system, whereas an excess of false negatives means patients will not get the refractive error correction they need. (cehjournal.org)
Clear lens extraction for the correction of high refractive error. (google.com)
Extrapolating these findings to the general US population, approximately 14 million individuals aged 12 years or older have visual impairment (defined as distance visual acuity of 20/50 or worse), and of these, more than 11 million individuals could have their vision improved to 20/40 or better with refractive correction. (nih.gov)
Providing appropriate refractive correction to those individuals whose vision can be improved is an important public health endeavor with implications for safety and quality of life. (nih.gov)
Eyes drops filled with synthetic nanoparticules have shown promising potential for a revolutionary alternative non-invasive correction of refractive errors," the authors reported in their study abstract, which analyzed the refractive errors of 10 pig eyes before and after the introduction of the nanodrops. (zmescience.com)
Refractive error and vision correction in a general sports-playing population. (aston.ac.uk)
Now the laser is FDA-approved for topography-guided laser vision correction as well, incorporating refractive error of the eye and corneal irregularities into custom laser ablations. (laservisiondelaware.com)
Typically used for vision correction, glasses come in many types and are classified by their primary function such as correcting refractive errors, magnification, sun protection and safety. (hermaneyecenter.com)

If you have refractive errors before middle age, you can also develop presbyopia on top of your other condition when you get older. (oculase.com)
The cost to train refractionists and maintain refractive services to deal with uncorrected refractive error (including presbyopia) is US $28 billion. (cehjournal.org)
This study aimed to determine the prevalence of REs among adults aged ≥30 years in India and the need for refractive services through estimates of the prevalence of URE and uncorrected presbyopia. (sightsavers.org)
If you're older than 40, you may have experienced one of the "joys" of aging: Our eyes change as we get older, inevitably developing a new refractive error called presbyopia. (eyesonmissouri.com)

Refractive error is diagnosed through visual acuity testing, refraction, or a comprehensive eye examination. (cdc.gov)
Refractive errors are diagnosed by visual acuity and refraction screening tests which are usually accompanied by a comprehensive clinical examination of the eye. (3d4medical.com)
Deviations from the average or standard indices of refraction of the eye through its dioptric or refractive apparatus. (ucdenver.edu)
Uncorrected refraction errors (URE) are a severe public health problem in view of their magnitude and also by the multiple consequences they cause around the world. (fortunejournals.com)
Your eye doctor will determine the type and degree of refractive error you have by performing a test called refraction. (scoallentown.com)
They then compared the predicted refraction with objective refractive outcomes 1 week, 1 month, and 3 months after surgery. (ophthalmology360.com)
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)
To meet the need for guidance in this area, the IAPB Refractive Error Working Group recently published a paper ( https://bit.ly/RE-paper ) which defines minimum criteria and recommendations for the quality and operating environment of screening, self-refraction, and self-prescribing devices. (cehjournal.org)
Visual impairment due to uncorrected refractive error was defined as (presenting) visual impairment that improved, aided by automated refraction results, to 20/40 or better in the better-seeing eye. (nih.gov)
The degree of refraction ( refractive index) by a medium of the wavelength is dependent of the on the incident light's dispersion. (thecustomizewindows.com)

According to the World Health Organization, an estimated 153 million people live with visual impairment due to uncorrected refractive errors. (seeintl.org)
The course aims at building the capacity of the national programs in tackling the burden of visual impairment that caused by low vision and refractive errors. (who.int)
Refractive errors such as short or long sightedness are the greatest cause of avoidable visual impairment among children. (who.int)
The global strategy of VISION 2020 focuses on visual impairment as a major public health problem and addresses its main causes including refractive errors and low vision. (who.int)
An exception to this difficulty is a series of population-based surveys of refractive error and associated visual impairment in school-age children conducted in five different geographic regions using a common protocol -the Refractive Error Survey in Children (RESC). (cehjournal.org)
Although some of the refractive error underlying clinically significant visual impairment was found to have been already corrected with spectacles, an essentially equal amount of correctable refractive error remained uncorrected (Figure 2). (cehjournal.org)
Although the relationship between uncorrected visual acuity and refractive error was not a precise one, among those with a relatively high prevalence of visual impairment, correspondingly high amounts of refractive error were found, as expected. (cehjournal.org)
The purpose of this thesis is to investigate potential key determinants of the success, or otherwise, of endeavours to address avoidable Visual Impairment (VI) by addressing Uncorrected Refractive Error (URE) in Mozambique and the wider region of sub-Saharan Africa by providing optometric services. (tudublin.ie)
Indeed, several studies have established the link between quality of life and visual impairment caused by refractive errors [4-11]. (fortunejournals.com)
Visual impairment due to uncorrected refractive error is a common condition in the United States. (nih.gov)

What Is Refractive Surgery? (medlineplus.gov)
Dhaliwal, 2015) Refractive error can be treated with corrective eye glasses, contact lenses, and refractive surgery. (cdc.gov)
Predictive value of slitlamp examinations in screening donor corneas for prior refractive surgery. (ucdenver.edu)
Farsightedness is treated with a convex lens or with refractive surgery. (scoallentown.com)
Refractive errors can also be treated with contact lenses or refractive surgery such as laser surgery. (operationeyesightindia.org)
Laser eye surgery is a simple corrective procedure to treat all kinds of refractive errors. (oculase.com)
In these cases, we may offer refractive lens exchange (lens replacement surgery). (oculase.com)
A Refractive Secondary Lens Implant is for people who've had cataract or lens replacement surgery and still need glasses. (oculase.com)
Refractive Surgery -It is also an option to correct or improve your vision. (shraddhaeyehospital.com)
Are you an ideal candidate for corneal refractive surgery? (shraddhaeyehospital.com)
What is the best way to predict pseudophakic refractive error in patients who are about to undergo cataract surgery? (ophthalmology360.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)
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)
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)
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)
While there is more than one type of refractive surgery, specific treatments are recommended on an individual basis. (yeagervisioncare.com)
As technology progresses, it is becoming more and more important that you explore all options and possibilities before deciding which refractive surgery and treatment is right for you. (yeagervisioncare.com)
Refractive surgery has entered the mainstream of general ophthalmology, with patients inquiring every day about their potential for the surgery or questioning the results of previous procedures. (google.com)
Now you have at your fingertips the first concise, easily accessible guide to modern refractive surgery, covering all major surgical procedures and offering expert clinical recommendations on when and how to use them. (google.com)
Written by highly experienced specialists, the book is designed for all members of the refractive surgery team, with the goal of turning to it for quick reference and confirmation of a diagnosis in every examining room! (google.com)
If you want a faster and more permanent solution, you may opt to have a refractive surgery such as LASIK . (filmannex.com)
For these people, sight can be restored with appropriate spectacles, contact lenses, or refractive surgery. (iapb.org)
While Dr. Barnes spoke about "refractive surgery", his testimony in the context of a special hearing on LASIK implied that his arguments were in support of the LASIK procedure. (lasiknewswire.com)
Indeed, the Summary Minutes of the FDA hearing state that, "Dr. Barnes of the Warfighter Refractive Eye Surgery Program emphasized the importance of LASIK to the military. (lasiknewswire.com)
LASIK surgery, also known as Laser-assisted in situ keratomileuses, is the option to correct the refractive errors. (ojaseyehospital.com)
Refractive services include Lasik surgery which is a tried and tested method for refractive errors. (eyeqindia.com)
Latest surgical options and procedures to correct refractive errors by refractive Lasik eye surgery in Bangalore. (atozholidaymedicare.net)
LASIK Eye Surgery LASIK eye surgery is an eye surgical procedure that remedies the refractive error of the eye. (wmartone.us)
Changes in refractive error due to surgery were computed by the ordinary rules of vector subtraction. (bikeradar.com)
Results: Frequency distributions of blur strength (B) clearly demonstrate the effectiveness of refractive surgery at reducing the overall blurring effect of uncorrected refractive error. (bikeradar.com)
For practical reasons, the general principles of excimer laser refractive surgery, which were ex-plained in the first report, are explained again in Appendix A. Also, a brief summary of ocular anatomy and the main refractive errors is repro-duced in the following section to make this re-port easier to understand by readers who might be less familiar with ophthalmology. (bvsalud.org)
The present report provides an update on refractive surgery since the publication of the 1997 report. (bvsalud.org)

Glasses or contact lenses can usually correct refractive errors. (medlineplus.gov)
Anyone can have refractive errors, but you're at higher risk if you have family members who wear glasses or contact lenses. (seeintl.org)
Correcting refractive errors is often easy to do with glasses or contact lenses. (oculase.com)
The best way to treat or correct refractive error is through the use of prescription glasses or contact lenses. (filmannex.com)

No matter which type of refractive error you have, an eye care specialist can diagnose and treat it. (clevelandclinic.org)
This is one type of refractive error. (yeagervisioncare.com)

The VEHSS team conducted a review of published literature on examination-based population studies reporting the prevalence of uncorrected refractive error. (cdc.gov)
There were 10 studies published between 2005 and 2016 that examined the prevalence of uncorrected refractive error. (cdc.gov)
Objective: The objective of this study was to determine the prevalence of uncorrected refractive error among students in three selected secondary schools in Birnin Kebbi metropolis as many children with poor vision due to refractive error remain undiagnosed and perform poorly in schools. (bvsalud.org)

Refractive disorders are usually detected through the tests administered in a routine eye exam. (scoallentown.com)
It's important to schedule an annual eye exam to diagnose and correct refractive disorders. (scoallentown.com)
In children, refractive errors are the most common vision disorders, occurring in 20 percent by 16 years of age. (cdc.gov)

Refractive error that is not diagnosed or treated is called uncorrected refractive error (URE). (cdc.gov)

When the delicate mechanics of the eye's optical elements fall out of balance, this leads to refractive error, also known as ametropia. (3d4medical.com)

The difference between presenting and uncorrected vision reflects the amount of refractive error that is already corrected, while the difference between presenting and best corrected vision indicates the extent to which uncorrected refractive error remains as a vision disabling problem. (cehjournal.org)
and the data do not correlate with the situation in optometric uncorrected refractive error remains one of the main education in the EMR ( 13 ). (who.int)

Most people with refractive errors develop them over time as they grow and develop. (clevelandclinic.org)

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)
The potential lost productivity as a result of uncorrected distance refractive error is US $268.8 billion per year. (cehjournal.org)

IMSEAR at SEARO: Intraocular pressure dynamics in different refractive errors. (who.int)

What are the symptoms of a refractive error? (clevelandclinic.org)
What are symptoms of refractive errors? (seeintl.org)
A refractive error can cause a number of symptoms. (visionenhancers.com)
Go to Refractive error symptoms on this page for more about these. (oculase.com)
Many eye conditions produce symptoms right away, but problems with refractive errors can be subtle at first. (oculase.com)
Even if your child exhibits no symptoms of a refractive error or other preschool vision problems, he should have an eye exam by the age of 6 months, again at age 3 years, and also prior to starting school. (allaboutvision.com)

Refractive errors may happen when the length of the eyeball grows too short or too long. (oculase.com)

Expression experiments and comprehensive in silico analyses identified retinal cell physiology and light processing as prominent mechanisms, and also identified functional contributions to refractive-error development in all cell types of the neurosensory retina, retinal pigment epithelium, vascular endothelium and extracellular matrix. (eur.nl)
Refractive errors are extremely common and they affect the ability of the eyes to focus light properly on the retina, at the back of the eyeball. (visionenhancers.com)
However, when there is a refractive error, the rays of light might be unable to meet at the retina. (visionenhancers.com)
Most common vision problems are caused by refractive errors - the eye's inability to focus, or refract, light correctly on the retina (the light-sensitive layer of tissue at the back of the eye). (scoallentown.com)
When the eye cannot focus light on the retina to create a sharp image then it results in a refractive error. (oculase.com)
Refractive Error is an eye disorder that results in hazy vision when the shape of your eye keeps light from focusing correctly on your retina. (felixhospital.com)
Refractive error occurs if the eye cannot focus light properly on the retina. (preventblindness.org)
The most common vision problems are refractive errors, which is when the shape of the eye prevents light from directly focusing on the retina. (arlingtoneyecenter.com)
Refractive errors occur when light does not correctly focus on the retina, which is the light-sensitive tissue at the back of the eye. (cdc.gov)
Refractive errors occur when there is no image formation on the retina. (ojaseyehospital.com)

Power vectors also provide a natural link to a more comprehensive optical description of ocular refractive imperfections in terms of wavefront aberration functions and their description by Zernike polynomials. (bikeradar.com)

A review of the 28,000 procedures has shown that soldiers with PRK or LASEK have a 20% greater chance of achieving an uncorrected visual acuity of 20/15 or better than soldiers with a similar level of refractive error undergoing LASIK. (lasiknewswire.com)

3. PRELEX (presbyopic refractive lens exchange) or clear lens extraction. (vostochnyde.info)

A refractive error is an eye disorder which results in the inability of the eye to clearly focus on objects, resulting in blurry vision. (3d4medical.com)
Blurry vision, either up close or at a distance, is the most common sign of a refractive disorder. (scoallentown.com)

En Algérie, le premier cas a été identifié le 25 février 2020, un plan de riposte national élaboré par le ministère de la santé a été mis en place pour affronter l'épidémie. (bvsalud.org)

Refractive error occurs when the eye cannot clearly focus on images, resulting in blurred vision 1 . (operationeyesightindia.org)
This eye condition occurs when vision in one eye is reduced because of a communication error between the brain and the affected eye. (cdc.gov)

We work with local partners in South Asia and Africa to bring diagnosis and optical services to people with refractive error, at little or no cost to them. (operationeyesightindia.org)

Wallace H, Misra S, Li S, McKelvie J. Predicting pseudophakic refractive error: Interplay of biometry prediction error, anterior chamber depth, and changes in corneal curvature. (ophthalmology360.com)
By utilizing this imaging technique, ophthalmologists and optometrists can detect even the slightest imperfections in a patient's corneal shape or curvature, which cause refractive errors. (skipjack.net)

2003. Decelopment of refractive error and strabismus in children with Down syndrome. (bvsalud.org)
Squint (Strabismus) is a condition which arises due to an incorrect balance of muscles, refractive errors, nerve palsy, and several other reasons. (eyeqindia.com)

Refractive errors are extremely common eye conditions that make your vision blurry. (clevelandclinic.org)
Refractive errors are some of the most common vision problems people experience. (clevelandclinic.org)
Refractive errors are surprisingly common, affecting a considerable amount of the population, so let's take a closer look. (3d4medical.com)
Refractive errors are one of the most common issues that a person can experience with their vision. (visionenhancers.com)
Refractive error conditions are common, so it's important to get eye examinations every two years. (oculase.com)
Refractive errors are the most common cause of eyesight problems according to the National Eye Institute. (filmannex.com)
Refractive error (RE) is one of the most common ocular conditions affecting all age groups. (sightsavers.org)

Effect of the body posture on visual acuity, refractive error and binocular vision. (uitm.edu.my)

And every single one of us will develop a vision problem, including refractive error [which makes it hard to see clearly] and cataracts, if we live long enough. (medlineplus.gov)

A refractive error is something about the natural shape of your eyes that makes your vision blurry. (clevelandclinic.org)

Investigators calculated optimum intraocular lens (IOL) power and predicted refractive outcomes using the Barrett Universal II, Hill-RBF, and SRK/T formulas. (ophthalmology360.com)

Designed for patients with higher degrees of refractive errors, the Implantable Collamer® Lens, or ICL™, was designed to be placed within an eye, overlying the eye's natural lens. (visionmaxeye.com)

From refractive error to dashed career opportunities, Kim Thomas discusses the lifelong consequences of amblyopia. (college-optometrists.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)

Refractive errors largely determines pupil performance in schools in Brazzaville, Congo. (ajol.info)
We examined the roles of pupil displacement and refractive error in the amount of corneal and ocular lateral coma aberration. (arvojournals.org)
Ocular lateral coma values were smaller than the corneal values and did not vary significantly with either pupil displacement or refractive error. (arvojournals.org)
The influence on unaided vision of age, pupil diameter and spherocylindrical refractive error. (aston.ac.uk)

In some cases, refractive services are provided, but an inadequate supply of spectacles makes these services irrelevant as people still have to live with uncorrected refractive error. (cehjournal.org)

In this study, subjects (eyes) will be recruited and divided into 4 groups, i.e. normal, cataract, significant refractive errors and retinal diseases. (who.int)

Operation Eyesight is also a proud member of the International Agency for the Prevention of Blindness's Refractive Error Coalition . (operationeyesightindia.org)

The ICL lens works with the natural eye lens for correcting refractive errors. (eyeqindia.com)

Refractive surgeries require healthy eyes that are free from retinal problems, corneal scars, and any eye disease. (yeagervisioncare.com)

There is a large market for visual training programs as ~150 million U.S. residents currently use some form of eyewear to correct refractive error. (aao.org)
Eyeglasses are the simplest and safest way to correct refractive errors. (scoallentown.com)
48. Bi-focal lens is used to correct ____________ refractive error. (askiitians.com)

To evaluate the impact of anti-vascular endothelial growth factor therapy on the refractive error in eyes with diabetic macular edema. (lww.com)
If you find yourself squinting in order to see objects far away in the distance, this is possibly a refractive error in your eyes. (3d4medical.com)
A refractive error can appear in either one eye or in both eyes and can also progress at a different pace in each eye. (visionenhancers.com)
If you have bad habits, such as smoking, and spend long hours in front of a screen or a book without allowing your eyes to rest, the chances of developing a refractive error can increase. (visionenhancers.com)
Computer-assisted measurement of retinal vessel diameters in the Beaver Dam Eye Study: methodology, correlation between eyes, and effect of refractive errors. (ucdenver.edu)
The refractive errors of the students' eyes were measured using non-cycloplegic autorefraction. (essilorluxottica.com)
If this was any lower, then we wouldn't be able to bend light clearly which is why if you open your eyes underwater everything is slightly out of focus because water has a lower refractive index. (optilase.com)
Retinoscopy- Retinoscopy is typically performed during a routine eye exam to determine if the eyes have a refractive error. (felixhospital.com)
Emmetropization is a normal developmental process in which the eyes growth is regulated to achieve a match between eye length and its refractive power. (berkeley.edu)

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)

therefore identifying and, if possible, addressing the source of this residual error could help surgeons to offer patients improved postoperative outcomes, increasing patient satisfaction with the technique. (ophthalmologytimes.com)

Anatomy12

Diseases26

Chemicals and Drugs3

Analytical, Diagnostic and Therapeutic Techniques and Equipment34

Psychiatry and Psychology7

Phenomena and Processes9

Disciplines and Occupations4

Anthropology, Education, Sociology and Social Phenomena2

Technology, Industry, Agriculture1

Information Science1

Named Groups2

Health Care11

Geographicals6

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

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

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

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

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

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

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

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

No images available that match "refractive errors"

Refractive Errors

Myopia

Hyperopia

Refraction, Ocular

Eyeglasses

Retinoscopy

Astigmatism

Accommodation, Ocular

Vision Screening

Visual Acuity

Axial Length, Eye

Emmetropia

Anisometropia

Biometry

Eye

Mydriatics

Strabismus

Vision Tests

Amblyopia

Cyclopentolate

Visually Impaired Persons

Vision, Low

Optometry

Presbyopia

Refractive Surgical Procedures

Vision Disorders

Eye Diseases

Corneal Topography

Sensory Deprivation

Pupil

Singapore

Esotropia

Anterior Chamber

Lenses

Blindness

Contact Lenses

Cornea

Prevalence

Aberrometry

Cataract

Myopia, Degenerative

Keratomileusis, Laser In Situ

Keratotomy, Radial

Lens, Crystalline

Interferometry

Photorefractive Keratectomy

East Timor

Lasers, Excimer

Lens Implantation, Intraocular

Age Distribution

Exotropia

Vitreous Body

Belize

Asian Continental Ancestry Group

Sex Distribution

Diagnostic Errors

Albinism, Ocular

Diagnostic Techniques, Ophthalmological

Tropicamide

Vision, Ocular

Optics and Photonics

Cross-Sectional Studies

Choroid

India

Contact Lenses, Hydrophilic

Tomography, Optical Coherence

Photography

Refractometry

Ophthalmology

Retinopathy of Prematurity

Convergence, Ocular

Diplopia

Vision, Monocular

Ocular Physiological Phenomena

Cataract Extraction

Urban Population

Arizona

Vision, Binocular

Pseudophakia

Fovea Centralis

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