Refractive errors, reading performance, and school achievement among Eskimo children.
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Alaska↗
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Cataract: refractive error, diabetes, and morphology.
A retrospective analysis of 388 records of patients undergoing surgery for cataract between the years 1968 and 1978 showed that more women than men were admitted. About 13.7% of the patients were diabetic, and there was a striking excess of women over men with diabetes and cataract. The diabetic patients required surgery at an earlier age than the non-diabetics. Patients who had been refracted at least 5 years before surgery showed an incidence of myopia of -1.00 D or more of 25.4%. In 34% of the whole series the aphakic refraction was less than +11.00 D, again suggesting that myopes are more likely to develop a cataract than non-myopes. Posterior subcapsular lens changes alone or in combination with nuclear or cortical opacities were present in over 40% of all patients and the mean age of patients with this type of change alone was significantly lower than patients with predominantly nuclear or cortical changes. Posterior subcapsular opacities seem to be more common in Iowa than in England or India. The morphological similarity of this type of lens change with known types of secondary cataract suggests that it is not entirely a senile change but may be due to environmental or dietetic factors.
Aged↗
Stereoscopic evoked responses to crossed and uncrossed disparity accompanying simulated refractive error.
Evoked potentials were recorded to the occurrence of a disparate stimulus in dynamic random dot stereograms. Seven adult males, all of whom had vision which was normal or corrected to normal, participated in the experiment. Subjects viewed 100 ms duration stimuli which embodied 30 arc min of either crossed or uncrossed disparity under four conditions of spherical overcorrection: -0.25, +1.0, +2.0, +3.0 dioptres. The first condition, essentially normal refraction, yielded reliable behavioural reports of the stimulus and clear evoked potentials to both crossed and uncrossed disparity. With increasing overcorrection the behavioural reports became less reliable, and the evoked potentials were degraded for both conditions of disparity. The responses to the crossed disparity condition, however, showed significantly less degradation in both behavioural and electrophysiological measures. The implications of this finding may be that there are separate cortical subsystems for the processing of crossed and uncrossed disparity and that the former is more robust under non-ideal viewing conditions.
Adult↗
[The practice guideline 'Refraction errors' from the Dutch College of General Practitioners: response from the perspective of ophthalmology].
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Clinical Competence↗
Shifts in tonic accommodation after near work are related to refractive errors in children.
A link between changes in tonic accommodation (TA) produced by sustained near work and the development of adult-onset myopia has been suggested in studies of young adults. Measures of TA before and after near work have been lacking in children of school age, which is the most susceptible period for the development and progression of juvenile-onset myopia. In the present study accommodation was measured in 87 children, aged 7 to 16 years, before and after 15 minutes of video game playing. All children were refracted before testing and wore optical correction during measures of accommodation with a Canon R1 autorefractor. Most children showed initial values of TA (far focus minus dark focus) between 0.0 and 1.0 D, with a mean of 0.68 D. Grouped by refractive status, the myopic children initially showed 0.30 D of TA, while the emmetropic children showed 0.75 D and the hyperopic children showed 0.94 D. After playing the video game, TA of the myopes increased by 1.15 D, compared to smaller increases for the emmetropes (0.68 D) and hyperopes (0.24 D). Comparable values have been obtained from young adults. These results indicate that the smallest initial values of TA and the largest inward shifts in TA are found during the period of acquisition and progression of myopia, regardless of age.
Accommodation, Ocular↗
Accommodation, refractive error and eye growth in chickens.
We raised chickens with defocusing lenses of differing powers in front of their eyes. For this purpose, small hoods made from soft, thin leather were carefully fitted to their heads. Lenses were attached to the hoods by velcro fasteners and could be easily removed for cleaning. The powers of the lenses were such that their optical effects could be compensated for by accommodation. It was verified by infrared (IR) photoretinoscopy that the chickens could keep their retinal images in focus. Wearing a lens resulted in a consistent shift of the non cycloplegic refractive state (measured without the lens) which was in the direction to compensate for the lens. We used a sensitive technique (precision = +/- 50 micron as estimated from the variability of repeated measurements) to measure the posterior nodal distance (PND) in excised eyes of birds grown with lenses. The PND, in turn, was used to compare eyes treated with different lenses. It was found that the PND was increased in eyes which were treated with negative lenses compared to those treated with positive lenses. This effect occurs independently in both eyes and it is not due to changes in corneal curvature. We discuss our result in terms of a closed-loop feedback system for the regulation of eye growth.
Accommodation, Ocular↗
The effect of refractive error on pattern electroretinograms in primates.
The effect of optical blur on the steady-state (6, 8, 10 Hz) counterphase pattern electroretinogram (PERG) was measured in three normal cynomolgus monkeys. Blur was induced using lenses of -8.00 to +12.00 diopters, and monocular PERGs were recorded at a viewing distance of 0.32 meters. A substantial decrease in PERG amplitude occurred with a 0.51 cpd grating when +4.00 diopters of blur or greater were used. PERG amplitude to a 1.25 cpd grating decreased with lenses greater than +2.00 diopters. Minus lenses caused a steep decline in PERG amplitude of both spatial frequency gratings. These results indicate that refractive state has a significant effect upon the PERG and should be carefully considered in electrophysiologic testing of the primate visual system.
Accommodation, Ocular↗
Age, gender, biometry, refractive error, and the anterior chamber angle among Alaskan Eskimos.
BACKGROUND: The prevalence of angle-closure glaucoma (ACG) is greater for Eskimos/Inuit than it is for any other ethnic group in the world. Although it has been suggested that this prevalence may be due to a population tendency toward shallower anterior chamber angles, available evidence for other populations such as Chinese with high rates of ACG has not consistently demonstrated such a tendency. METHODS: A reticule, slit-lamp, and standard Goldmann one-mirror goniolens were used to make measurements in the anterior chamber (AC) angle according to a previously reported protocol for biometric gonioscopy (BG) (Ophthalmology 1999;106:2161-7). Measurements were made in all four quadrants of one eye among 133 phakic Alaskan Eskimos aged 40 years and older. Automatic refraction, dilated examination of the anterior segment and optic nerve, and A-scan measurements of AC depth, lens thickness, and axial length were also carried out for all subjects. RESULTS: Both central and peripheral AC measurements for the Eskimo subjects were significantly lower than those previously reported by us for Chinese, blacks, and whites under the identical protocol. Eskimos also seemed to have somewhat more hyperopia. There were no differences in biometric measurements between men and women in this Eskimo population. Angle measurements by BG seemed to decline more rapidly over life among Eskimos and Chinese than blacks or whites. Although there was a significant apparent decrease in AC depth, increase in lens thickness, and increase in hyperopia with age among Eskimos, all of these trends seemed to reverse in the seventh decade and beyond. CONCLUSIONS: Eskimos do seem to have shallower ACs than do other racial groups. Measurements of the AC angle seem to decline more rapidly over life among Eskimos than among blacks or whites, a phenomenon also observed by us among Chinese, another group with high ACG prevalence. This apparent more rapid decline may be due to a cohort effect with higher prevalence of myopia and resulting wider angles among younger Eskimos and Chinese.
Adult↗
The effect of continuous light on refractive error and the ocular components of the rat.
Phototoxic induced degeneration of the rat retina is a well-documented phenomenon resulting in losses of photoreceptors and their cell bodies, and an overall retinal thinning. This process may serve as a test of the hypothesis that the retinoscopic reflex originates from the inner limiting membrane of the retina. Retinal thinning should produce myopia in the absence of any other ocular component changes in a stable, mature eye if the inner limiting membrane model is correct. Phototoxic retinal degeneration was induced in 10 albino rats by exposure to 19 days of continuous light (1,800 cd m-2). Another 10 albino rats exposed to 12-hr on/12-hr off cycled light served as controls. Before and after the exposure to constant light, measures were made of refractive state by cycloplegic retinoscopy, corneal curvature and lens curvature by Purkinje image photography, and axial length of the globe by A-scan ultrasonography. Comparing pre- to post-exposure values, phototoxic degeneration resulted in a mean (+/- S.D.) myopic shift of -5.10 +/- 2.12 D (P < 0.002). The corneal curvature also steepened significantly (0.17 +/- 0.11 mm, equivalent to -6.0 D; P < 0.004), while the posterior curvature of the crystalline lens flattened by 0.21 +/- 0.22 equivalent mm (P < 0.027), and the axial length shortened by 0.11 +/- 0.11 equivalent mm (all tests Wilcoxon signed-rank; P < 0.025). Phototoxic rats underwent a mean retinal thinning of 49.6 mu compared to controls (Kruskal-Wallis test; P < 0.0008). No refractive or ocular parameters changed significantly in the controls. Phototoxic degeneration in the rat has optical consequences beyond simple retinal thinning. The size of the eye and the curvature of refractive surfaces can be altered in a mature eye well after the completion of development. The multiple changes which occur prevent phototoxic retinal thinning from serving as a test of the inner limiting membrane model for retinoscopic reflections.
Animals↗
Inflammatory response, endophthalmitis, corneal dystrophy, glaucoma, retinal detachment, dislocation, refractive error, lens removal, and enucleation.
This paper provides a synopis of published data on most of the major complications of the implantation of currently used intraocular lenses. With one exception, these studies lack controls, and the results show the variations expected when a variety of lens implants, techniques, and surgeons are compared. The author's personal data are also included.
Bacterial Infections↗
Prevalence of refractive errors and ocular motility disorders in 5- to 10-year-old Swedish children born prematurely or at full-term.
Knowledge of the occurrence of visual and ocular problems in children is important when eye health care systems are designed. We have studied the prevalence of ocular changes in all children born prematurely during 1976-1981 in Stockholm county and compared the findings with those obtained in a random sample of full-term children from the same period and area.
Child↗
A survey on refractive error and strabismus among children in a school at Aligarh.
An ophthalmic survey of 310 school going children in the age group of 4-12 years was done. 41 children (13.2%) were found to have a vision of less than 6/6 in one or both eyes. Myopia of 0.5 D or more and hyperopia of +2 D or more or astigmatism of 1 D or more in one or both eyes were seen in 74 children (22.9%). There was a tendency for a decrease in hyperopia and an increase in myopia with advancing age. Astigmatic error of 1 D or less was seen in 12 eyes (1.93%) and anisometropia of more than 1 D was present in 11 cases (3.5%). Hypertropia was more in female children whereas myopia had a nearly equal distribution in both sexes. There was heterophoria and manifest strabismus which showed a gradual increase with advancing age. This study was compared to few other studies undertaken in the past.
Child↗
Refractive state and correction of refractive errors among mentally retarded adults in a central institution.
In a population of 212 mentally retarded, retinoscopy could be performed in 342 eyes in 182 patients. Of these, 334 eyes were phakic. Hypermetropia of +5 or more was encountered in 20 eyes (6.0%), while 26 (7.8%) had a myopia of -5 or more. The most striking finding was a high number of severe astigmatism, cylindrical power of -3.25 or more being present in 29 eyes (8.7%). Glasses were initially prescribed to 88 patients. Six months after the prescription, 59.1% used their glasses regularly. Aspects of glass prescription to mentally retarded are discussed in the paper.
Adolescent↗
The accommodative response, refractive error and mental effort: 1. The sympathetic nervous system.
The accommodative response of 12 emmetropic subjects was measured for an array of numbers located at -1, -3 and -5 dioptres using an objective infra-red optometer. Responses were compared for passive (reading numbers) and active (adding numbers) conditions. The imposition of mental effort induced a significant increase in mean response for the -1 D stimulus, a response equivalent to the passive condition at -3 D and a reduction in response at -5 D. Mental effort induced similar responses for the -1 D and -3 D locations when sympathetic innervation to the ciliary muscle was blocked with the beta-receptor antagonist timolol maleate. Responses for the -5 D location were, however, significantly increased. It is proposed that sympathetic inhibition can modify the effect of mental effort on near accommodative responses.
Accommodation, Ocular↗
Prediction of aphakic refractive error in children.
Formulas created to predict the optical requirements of the aphakic eye have been tested mainly in adult eyes. The accuracy of these formulas in shorter pediatric aphakic eyes was examined using retrospective analysis of 17 aphakic pediatric patients. The Sanders-Retzlaff-Kraff contact lens formula, used previously to predict required lens powers for epikeratophakia, consistently underestimated the required aphakic correction in the shorter eyes, which may have been responsible in part for the large undercorrections obtained previously in patients under one year of age. The Hoffer-Colenbrander and Binkhorst theoretical formulas, Donzis-Kastl-Gordon percentage change formula, and a linear regression formula derived from the present data (LIN), were significantly more accurate. The differences between these formulas were not significant. The use of one of these formulas should facilitate prediction of required epikeratophakia lenticule power or intraocular lens power in young children.
Aphakia, Postcataract↗
Assessment of just-noticeable differences for refractive errors and spherical aberration using visual simulation.
PURPOSE: The aim of this study was to evaluate the threshold levels of aberration change that a typical reference eye is able to detect. METHODS: The method involved simulation of the foveal vision of a typical eye in polychromatic light through optics affected by different levels of the various chosen monochromatic aberrations. The reference eye had the following monochromatic wavefront characteristics based on the aberrations of a population of young adults: no spherical defocus, astigmatism -0.37D oriented at 0 degrees celsius, coma -0.17 D/mm oriented at 270 degrees celsius, and spherical aberration -0.12 D/mm. Average amounts of longitudinal and transverse chromatic aberration were assumed, and allowance was made for the Stiles-Crawford effect. The pupil diameter of the simulated eye was kept fixed at 6 mm. Three observers each compared, 100 times, a simulated image as seen through the standard reference eye with a variant "aberrated" image. The varying parameter was the value of a chosen additional aberration affecting the variant image in the reference eye. The test was repeated for varying amounts of spherical defocus, astigmatic defocus, and spherical aberration. For each of these aberrations and each observer, the discrimination probability as a function of the aberration level in the variant image was determined. The just-noticeable difference in aberration (JNDA) was derived from each discrimination curve as the difference between the aberrations corresponding to discrimination probabilities of 75% and 25%. The JNDA values obtained were expressed in the form of root mean square (RMS) wavefront error thresholds. RESULTS: It was found that 0.04 microm of RMS aberration should be considered as the threshold of just-noticeable image change, in good agreement with the Maréchal criterion. CONCLUSIONS: The results imply that in normal viewing conditions (e.g., a 3-mm pupil size), optical corrections should be in the range of +/-0.15 D in sphere and cylinder from the target prescription if perceptible change in the quality of the perceived images is to be avoided. The design of conventional soft contact lenses of high negative power or positive power should aim to produce -0.07 D/mm of spherical aberration, with a tolerated interval between -0.15 to +0.01 D/mm for a 6-mm pupil size.
Adult↗
Prevalence of refractive errors on a VOSH mission to Nicaragua.
BACKGROUND: Optometric services in many parts of the world are unavailable with a resultant lack of information on the epidemiology of visual problems in those countries as well. METHODS: A retrospective analysis was conducted on the records of 3,281 patients seen on a VOSH mission to Nicaragua. RESULTS: The mean spherical correction for each eye was a low hyperopic correction. For eyes having an astigmatism the mean cylinder correction was -1.00 and was usually oriented against the rule. CONCLUSION: There was a lower incidence of myopia in this population than for many others that have been studied. There was also a need for a presbyopic correction at an earlier age than for Mid-European populations. A very large number of spectacles must be donated in order to get a sufficient supply for a successful VOSH mission.
Adolescent↗
Sex differences in refraction errors up to the age of 15.
A health inquiry concerning vision and corrective lenses at the age of 14 was carried out in a northern Finland series about 12,000 children followed up since birth. Data were obtained from more than 99% of cases. 34% of the girls and 18% of the boys had corrective lenses. 55% of the study population were living in the province of Oulu, and the ophthalmological records of these children were analysed (N 1939). The ophthalmological records covered 67% of the children with lenses in the province of Oulu. 71% of the girls with lenses, and 66% of the boys had these for myopia, both myopia and hyperopia were less common among the boys, but the cases were more pronounced. The children with lenses were on average taller and heavier and the myopic children had a better mean ability at school.
Adolescent↗