Errors of refraction and the use of glasses.
Explore the source record for details and available documents.
Eyeglasses↗
SEARCH · Search PubMed
Results for “refractive error”
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Studies on the development of errors of refraction in schoolchildren.
Explore the source record for details and available documents.
Adolescent↗
Use of an ophthalmoscope for objective refraction of noncooperative patients.
Refractive ophthalmoscopy was performed on 16 subjects aged 5 to 27 years. Subjective refractions were performed on both eyes of the subjects followed by an ophthalmoscopic determination performed under cycloplegia by the authors. A 0.94 correlation was found between the subjectively determined "dry" refractive error and the refractive error determined ophthalmoscopically under cycloplegia by both examiners. The results of the two procedures differed by 1 D or less 82% of the time. The results indicate that refractive ophthalmoscopy is an alternative method for objectively determining refractive error in non-cooperative patients with poor fixational stability.
Adolescent↗
The repeatability of measurement of the ocular components.
Studies of the ocular components of refraction typically neglect issues of repeatability of measurement methods or analyze method comparison/repeatability data inappropriately using correlation. The authors have examined the repeatability of refractive error measures (retinoscopy, subjective refraction, and Canon R-1 autorefraction, noncycloplegic and cycloplegic), axial dimension measures (Allergan-Humphrey A-scan ultrasound), and corneoscopy (keratometry and KERA photokeratoscopy), and the agreement between different refractive error and corneal measurement methods on 40 pre-presbyopic normal adults. The authors plotted the difference versus the mean of two different measurement occasions (repeatability), or two different methods (agreement), to determine the bias (mean of the differences relative to zero) and 95% limits of agreement of each technique. The most reliable measure of refractive error was autorefraction with cycloplegia, with 95% limits of agreement of +/- 0.32 diopters. Cycloplegic autorefraction had no statistically significant bias compared to cycloplegic subjective refraction. Cycloplegic retinoscopy was the least reliable refractive error measure, with repeat measures on two separate occasions extending over 95% limits of agreement of +/- 0.95 D. Anterior chamber depth was reliable to +/- 0.29 mm, lens thickness to +/- 0.20 mm, and vitreous chamber depth to +/- 0.37 mm. Corneal curvature measures show keratometry to be more reliable (to +/- 0.87 D) than photokeratoscopy (+/- 2.02 D) with a statistically significant bias (paired t-test, P less than 0.0001) of 0.57 D flatter for photokeratoscopy.
Adult↗
Calibration and validity of an eccentric photorefractor.
A new graphical calibration method was developed to convert the photorefractive reflex into refractive error. With this graphical method, the refractive error can be obtained for pupil sizes and for photorefractive reflex sizes which have not been precalibrated. In the conventional method, the refractive error associated with non-precalibrated pupil and reflex sizes is obtained by interpolating between neighbouring precalibrated points. This introduces error because the relationship between refractive error and pupil and reflex size is not linear. Three hundred and sixty-one children aged between 36 and 65 months were clinically examined and photorefracted. The refractive error obtained using retinoscopy and the eccentric photorefractor agreed well with each other, although the photorefractor tended to under-estimate refractive error. Using the referral criteria developed by Chan, O.Y.C. and Edwards, L.M. (Refraction referral criteria for Hong Kong Chinese Children. Ophthal. Physiol. Opt. 14, 259-256, 1994), the photorefractor had a sensitivity of 74.6% and a specificity of 96.4%. All the under-referred cases were borderline, having just failed the referral criteria. All the cases with hyperopia of > + 2.0 D, astigmatism of > 1.25 D and visual acuity of worse than 6/18 were identified.
Calibration↗
Albinism: its implications for refractive development.
PURPOSE: Albinism involves the mutation of one or more of the genes associated with melanin synthesis and has many ramifications for vision. This study focuses on the refractive implications of albinism in the context of emmetropization. METHODS: Refractive, biometric, and visual acuity data were collected for a group of 25 albino individuals that included the following: 18 oculocutaneous (13 tyrosine positive, 5 tyrosine negative); 7 ocular (2 autosomal recessive, 5 sex-linked recessive). Their age range was 3 to 51 years. All exhibited horizontal pendular nystagmus. RESULTS: There were no statistically significant differences relating to albino subtype for any of the measured parameters. All the subjects had reduced visual acuity (mean: 0.90, logMAR) and overall, there was a bias toward hyperopia in their refractive errors (mean: + 1.07 D). However the refractive errors of the group covered a broad range (SD: 4.67 D) and included both high myopia and high hyperopia. An axial origin to the refractive errors is implied by the high correlation between refractive errors and axial lengths. Refractive astigmatism averaged 2.37 D and was consistently with-the-rule and highly correlated with corneal astigmatism, which was also with-the-rule. Meridional analysis of the refractive data indicated that the vertical meridian for hyperopic subjects was consistently nearer emmetropia compared to their horizontal meridian. Myopic subjects showed the opposite trend. CONCLUSIONS: The overall refractive profile of the subjects is consistent with emmetropization being impaired in albinism. However, the refractive errors of hyperopic subjects also can be explained in terms of "meridional emmetropization." The contrasting refractive profiles of myopic subjects may reflect operational constraints of the emmetropization process.
Adolescent↗
Effect of localized defocus on detection thresholds for different sized targets in the fovea and periphery.
PURPOSE: Previous studies of optical blur in perimetry have measured the effect of foveal refractive error on peripheral perimetric detection thresholds. Since peripheral refractive error can be significantly different from that of the fovea we wished to remove the ambiguity of previous results by correcting the actual peripheral refractive error first before adding blur. METHODS: We measured detection thresholds in the fovea and at 30 degrees in the horizontal temporal field in two trained observers. Peripheral refractive error was determined at each location and thresholds measured at the same locations for stimuli ranging in size from 0.2 to 6.4 degrees and refractive errors between +/-4.00 diopters. RESULTS: Foveal thresholds increased immediately with increasing refractive error, particularly for smaller stimulus sizes. At 30 degrees, thresholds for smaller stimuli were less affected by defocus initially and then increased more sharply. Larger stimuli were relatively unaffected by defocus such that when stimulus size reached 1.6 degrees there was little or no increase in threshold for refractive error between +/-4.00 diopters. CONCLUSIONS: Peripheral refractive error, largely forgotten by perimetrists, has a significant effect on performance, particularly for smaller stimuli. Differences in foveal vs peripheral viewing can be explained by differences in ganglion cell receptive field sizes.
Fovea Centralis↗
Animal Models of Myopia: Learning How Vision Controls the Size of the Eye.
As they grow up, approximately 25% of children in the United States become myopic (nearsighted). A much smaller fraction become significantly hyperopic (farsighted), while the majority develop little or no refractive error and are emmetropic. The causes of refractive error, especially myopia, have been the subject of debate for more than a century. Some have held that myopia is primarily an inherited disorder, and others, that myopia is caused by protracted near work and, especially, by accommodation during protracted near work. It has not been possible, based solely on clinical observations, to resolve the relative roles of heredity versus environment in the development of refractive error. In the mid-1970s, several animal models were developed to study the mechanisms underlying refractive error. Using animal models, it was found that the visual environment exerts a powerful influence on refractive state by controlling the axial length of the eye during the postnatal developmental period. Although several species have been examined, three have emerged as primary models and have played complementary roles: tree shrews (mammals closely related to primates), chicks, and monkeys. Each has advantages and disadvantages. Collectively, research on animal models has provided evidence on three issues, namely that (1) the visual environment can produce refractive error; (2) an emmetropization mechanism normally guides eyes to low refractive error; and (3) under-accommodation, rather than excessive accommodation, may cause myopia. Two decades of research on animal models have provided criteria that may be used to evaluate the usefulness of additional species as models of emmetropization.
Journal Article↗
Power vector analysis of the optical outcome of refractive surgery.
PURPOSE: To demonstrate the power vector method of representing and analyzing spherocylindrical refractive errors. SETTING: School of Optometry, Indiana University, Bloomington, Indiana, USA. METHODS: Manifest and keratometric refractive errors were expressed as power vectors suitable for plotting as points in a 3-dimensional dioptric space. The 3 Cartesian coordinates (x, y, z) of each power vector correspond to the powers of 3 lenses that, in combination, fulfill a refractive prescription: a spherical lens of power M, a Jackson crossed cylinder of power J0 with axes at 90 degrees and 180 degrees, and a Jackson crossed cylinder of power J45 with axes at 45 degrees and 135 degrees. The Pythagorean length of the power vector, B, is a measure of overall blurring strength of a spherocylindrical lens or refractive error. Changes in refractive error due to surgery were computed by the ordinary rules of vector subtraction. RESULTS: Frequency distributions of blur strength (B) clearly demonstrate the effectiveness of refractive surgery in reducing the overall blurring effect of uncorrected refractive error. CONCLUSIONS: Power vector analysis also revealed a reduction in the astigmatic component of these refractive errors. Paired comparisons revealed that the change in manifest astigmatism due to surgery was well correlated with the change in keratometric astigmatism. Power vectors aid the visualization of complex changes in refractive error by tracing a trajectory in a uniform dioptric space. The Cartesian components of a power vector are mutually independent, which simplifies mathematical and statistical analysis of refractive errors. 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.
Astigmatism↗
Pinhole eyewear systems: a special report.
Multiple pinhole discs are being promoted as part of systems claimed capable of correcting refractive error. Attempts to mitigate refractive error utilize training attributable to the systems of Bates, Peppard, and Huxley. The pinhole discs provide an array of 0.9mm apertures separated by 3mm horizontally and vertically. Because of the small aperture size, some of the optical advantages of the pinhole are offset by diffraction effects. The discs can produce multiple images and the visual experience of individuals will be a function of the user's pupil size and refractive error. These are discussed both theoretically and based on the author's observations wearing the spectacles.
Equipment Design↗
Race-, age-, gender-, and refractive error-related differences in the normal optic disc.
OBJECTIVE: To determine race-, age-, gender-, and refractive error-related differences in the size and topography of the optic disc in healthy Americans. DESIGN: Population-based study. SETTING: Eastern and southeastern health districts of Baltimore, Md. PARTICIPANTS: A population-based sample of 4877 non-institutionalized black and white individuals aged 40 years or older without evidence of optic nerve disease. MAIN OUTCOME MEASURE: Race-, age-, gender-, and refractive error-related differences in optic disc measurements: disc area, neural rim area, cup area, cup-to-disc ratio, and neural rim area-to-disc area ratio. RESULTS: We analyzed simultaneous stereoscopic optic disc photographs from 3387 (1534 black and 1853 white) of the 4877 healthy individuals using an image analyzer (Topcon Image Analyzer, Topcon Instrument Corporation, Paramus, NJ). A total of 1490 individuals were excluded owing to the absence of good-quality images from either eye. The image analyzer defined the cup margin 150 microns below the surface of the disc margin. On average, blacks had significantly larger disc areas (blacks, 2.94 mm2; whites, 2.63 mm2), larger cup areas (blacks, 1.04 mm2; whites, 0.71 mm2), larger cup-to-disc ratios (blacks, 0.56; whites, 0.49), similar neural rim areas (blacks, 1.90 mm2; whites, 1.92 mm2), and smaller neural rim area-to-disc area ratios (blacks, 0.66; whites, 0.74) compared with whites. There were no age-related differences in any of the disc measurements. Male subjects had 2% to 3% larger optic discs compared with female subjects. No association between refractive error and any of the optic disc measurements studied was detected. CONCLUSIONS: Racial differences in the normal optic disc are present among urban Americans, and these differences must be considered in evaluation of the optic disc for glaucoma and other optic neuropathies. Among the individuals in our study, all of whom were 40 years of age or older, no progressive age-related decline in neural rim area was detectable. Neither gender nor refractive error were associated with any significant differences in the size and topography of the normal optic disc.
Adult↗
Refractive changes of congenital entropion and epiblepharon on surgical correction.
In order to investigate the refractive error, amblyopic frequency, and refractive change, if any, following recovery of cornea injury through surgery of epiblepharon and congenital entropion patients, we retrospectively reviewed the sex distribution, age at operation, chief complaints, preoperative and postoperative refractive errors, and best corrected visual acuity in 160 previously operated patients. The average age at operation was 7.9 years. The preoperative best corrected visual acuity of 133 eyes (41.6%) was below 5/9. Ninety-five eyes (29.7%) were preoperative myopes above -1.0D; 77 eyes (24%) were hyperopes above +1.0D; and 163 eyes were astigmatic above -1.0D. Of 228 eyes that were followed up for more than one year, 66 eyes demonstrated a best corrected visual acuity of below 5/9. There was no significant difference in the change in corneal astigmatism following surgery between the group under the age of 7 and the group over the age of 7. However, the mean best corrected visual acuity at postoperative one year was 6/9, which was significantly different from the preoperative value (P=0.006). Concurrent postoperative glasses correction and amblyopic therapy is indicated because the incidence of refractive errors and amblyopia is higher in epiblepharon and congenital entropion.
Adolescent↗
Light-intensity distribution in eccentric photorefraction crescents.
We try to improve the accuracy of eccentric photorefraction by taking more information into account than just the size and tilt of the crescent. Based on Gaussian optics and the assumption of an isotropic scattering retina, a theoretical analysis of the light-intensity distribution in the pupils of astigmatic eyes is presented. The method is applied to different photorefractor setups (point light source, long linear light source, knife-edge aperture, and circular aperture). In the case of a knife-edge aperture the crescent structure can be formulated analytically. In the case of a circular aperture an analytic description is possible only for spherical refractive errors, but astigmatic refractive errors can be determined from crescent parameters with neural networks.
Animals↗
Corneal aberrations and reading.
PURPOSE: To investigate the effects of eyelid pressure on corneal shape and corneal aberrations during reading. METHODS: Twenty young subjects with normal ocular health were recruited for the study. The experiment was conducted early in the morning, with subjects instructed not to perform any prolonged reading before the experiment. Corneal topography of one eye was measured with a videokeratoscope before reading and then again after a 60-min reading task. The natural position of the eyelids was photographed in primary gaze and during the reading task. RESULTS: Twelve of the 20 corneas showed significant changes in central topography immediately after reading. The location of the changes corresponded closely to the position and angle of the subject's eyelids during reading. The change in shape was best described as a wave-like distortion that significantly altered some corneal wavefront Zernike coefficients. There was a significant correlation between the changes in primary vertical coma and trefoil (along 30 degrees). Within the central 6 mm of the cornea, there were significant changes in the root mean square error, overall refractive power, and astigmatism. CONCLUSIONS: The changes we observed in corneal topography appear to be directly related to the force exerted by the eyelids during reading. Because the cornea is the major light-refracting surface of the eye, the optical characteristics of some eyes can be significantly changed during reading by the force of the eyelids. These findings may have important implications for the definition of refractive status and may also aid in the understanding of the relationship between reading and the development of refractive errors.
Adult↗
[Refractive changes in concomitant exodeviations].
UNLABELLED: The paper represents the analysis of 27 patients with a form of exodeviation examined în the Department of Ophthalmology Sibiu (jan. 1999-jan. 2003). METHOD: The evaluated parameters were: debut age, sensorial status, refraction, type of exodeviation related with refractive errors and treatment. RESULTS: The predominant refractive error was hyperopia (low degree)-40.74%, exophoria was the most frequent type of exodeviation (44.44%). Amblyopia was present în 11.2% of cases, 25.9% of patients had no stereopsis. CONCLUSIONS: In the studied group 81.48% of cases had refractive errors. Exophoria and intermittent exotropia were related with emetropia or minor refractive errors. Mixed astigmatism with amblyopia and anizometropia presented constant exodeviation.
Adolescent↗
Idiopathic macular hypoplasia: a report of four cases and refinement of the phenotype of so-called ateliotic macula.
PURPOSE: To refine the phenotype of idiopathic macular hypoplasia, also referred to as ateliotic macula, by describing a series of cases with this diagnosis. METHODS: A review of the clinical characteristics of four patients as documented in medical records with regard to refractive error, visual acuity, anterior segment examination, retinal findings, and ancillary tests such as electroretinography (ERG). RESULTS: All patients had oval circumscribed or diffuse areas in the posterior pole where the retina appeared not to have developed normally; the fovea was involved in three patients with reduced visual acuity, and one patient had parafoveal lesions with preserved visual acuity. There were three males and one females. Patients' age ranged from 4 to 16 years. Errors of refraction ranged from severe myopia to hypermetropia and mild astigmatism. The anterior segment was normal in all patients. Three patients had strabismus and two had nystagmus. ERG was normal in the one patient in whom it was performed. One patient was mosaic for trisomy of chromosome 9. CONCLUSIONS: The term idiopathic macular hypoplasia can be applied to a spectrum of abnormalities in which a localized area of the posterior pole has a primordial or underdeveloped appearance. Lesions involving the fovea result in poor acuity. Generalized retinal dysfunction is absent. At least one of the genes involved in macular development may be located on chromosome 9.
Adolescent↗
The effect of overnight contact lens corneal reshaping on refractive error-specific quality of life.
PURPOSE: The purpose of this study is to determine the effect of corneal refractive therapy (CRT) on refractive error-specific quality of life. METHODS: The National Eye Institute Refractive Error Quality of Life Instrument (NEI RQL-42) was administered to 20 myopic patients (mean spherical equivalent -3.11 D +/- 0.96 D) between the ages of 21 and 37 years both before and 1 month after being successfully fit with Paragon CRT lenses. High- and low-contrast best-corrected visual acuity (BCVA) and higher-order aberrations were also measured. Scores for the 13 NEI RQL-42 subscales were calculated and a Wilcoxon sign rank test was used to determine whether there was a significant change in each of the subscale scores. Post hoc power analyses were also performed. RESULTS: Statistically significant changes were found in three of the 13 NEI RQL-42 subscales. Significant improvements in subscale score were found for the symptoms (mean +/- standard deviation, 10.18 +/- 10.57, p = 0.0007) and dependence on correction (43.13 +/- 27.42, p < 0.0001) subscales. A significant reduction was found in the glare subscale (-32.50 +/- 35.22, p = 0.001). No significant changes were found in the clarity of vision, expectations, near vision, far vision, diurnal fluctuations, activity limitations, worry, suboptimal correction, appearance, or satisfaction with correction subscales. CONCLUSIONS: CRT may improve a patient's perception of their visual independence, decrease the amount of ocular symptoms they report, and increase symptoms of glare. A larger, well-controlled clinical trial is necessary to verify these results. An increase in patient-reported glare is likely the result of measured increases in higher-order aberrations after CRT, especially spherical aberration under mesopic and scotopic conditions.
Adult↗
A statistical analysis of the Biological Theory of spherical error of refraction.
It is widely believed that Adolph Steiger proved in Die Entstehung der sphärischen Refraktionen des menschlichen Auges (The Origin of Spherical Refractions of the Human Eye) that the Biological Theory of spherical error of refraction statistically explains the entire distribution of such errors, hence excluding other theories such as the Use-Abuse Theory. Although Steiger's Biological Theory is a statistical argument, he never put it into formal notation. This paper puts a modernized version of the Biological Theory into formal statistical notation. It shows that the Biological Theory explains the dispersion of distributions of spherical error of refraction but not the location of their means. The Use-Abuse Theory is an explanation of mean spherical error in populations. Since a complete theory of spherical errors of refraction needs to explain both the mean and the dispersion of their distribution, the two theories are potentially complementary. No empirical evidence, however, is presented here for either theory.
Eye↗