Distribution Of Refractive Errors Research Articles

The distribution of refractive errors in Nigeria

The distribution of refractive errors in Nigeria

Ocular findings among mentally retarded children in Finland.

The distribution of refractive errors, astigmatism, anisometropia, visual acuity and organic ophthalmic diseases were determined among 149 Finnish mentally retarded (IQ less than 70) children, aged 9-10 years. The case group was classified in 3 categories according to the degree of mental retardation. The control group (n = 100) was selected by random sampling.

Cylindrical Refractive Error

The distribution of cylindrical refractive error (right eye only) is presented for 957 persons, comprising approximately 80% of the population (aged 5 years and over) of three western Newfoundland communities. In 72% of males and 60% of females no cylindrical error was found; 12% of males and 19% of females had errors greater than 0.5 D. Cylindrical errors of 2 D or greater were found in 2.5% of females of but only 0.5% of males, affecting females of all ages but males aged less than 15 years only. Persons aged 45 years and up had fewer cylindrical errors, more against-the-rule and less with-the-rule astigmatism than persons below that age. Cylindrical error and spherical error, and in particular against-the-rule error and myopia, commonly occurred together. Among persons aged 5 to 14 years an association of with-the-rule error with nearwork is suggested.

An examination of refractive error through computer simulation.

Computer simulation is used to investigate the distribution of refractive error, generating two models based on corneal power, anterior chamber depth, lens power, and axial length for several samples (N = 1000). Discrepancies between simulated and observed data indicate that emmetropization is a more complex process than is accounted for by intercorrelations among components.

On emmetropization

The growth of the ocular elements, such as axial length, corneal power, and lens power, is represented by a set of first order, linear, coupled differential equations. Since the rate of growth and the size of the ocular elements vary from one individual to the next, the parameters which arise in these differential equations are assumed to be Gaussian random variables. These assumptions provide a basis for understanding the controlled growth of the eye. They predict that the distribution of refractive error is normal at birth and leptokurtic in adulthood. They also predict that the variance of refractive error will decrease with age provided the second order moments of the random variables obey some rather general conditions.

Correlation of Aphakic Retinal Detachment and Refractive Error with Gender

I analyzed the aphakic refractive errors of men and women separately in a statistical study of patients with aphakic retinal detachments. I compared the distribution of aphakic refractive errors in a population of 81 adult patients with nontraumatic aphakic retinal detachment with that of a randomly selected control population of 93 adult patients with aphakia. As a group, women who developed aphakic retinal detachments were significantly more myopic than female controls (11.41 vs 12.37 diopters of spherical equivalent; P = .004). In contrast, the refractive error in men did not differ between the aphakic retinal detachment and control groups (11.31 vs 11.68 diopters; P = .156). A significantly higher percentage of patients with bilateral (87%) aphakic retinal detachments were men (P = .017). In men other risk factors for aphakic retinal detachment, including cardiovascular disease, may overshadow the influence of axial myopia.

Optometric screening in achondroplasia, diastrophic dysplasia, and spondyloepiphyseal dysplasia congenita.

Visual screening tests were done on 61 individuals with various types of genetic skeletal dysplasias to determine which, if any, refractive errors are associated with each type. In individuals with achondroplasia, refractive error distribution was approximately that expected from its distribution in the general population. However, there was a significantly higher than expected frequency of strabismus in achondroplasts. A tendency to myopia was noted in diastrophic dysplasia and in those individuals with spondyloepiphyseal dysplasia.

A clinical analysis of pseudopapilledema. I. Population, laterality, acuity, refractive error, ophthalmoscopic characteristics, and coincident disease.

To clarify clinical features of pseudopapilledema, 142 cases (250 eyes) were analyzed regarding sex, age, race, bilaterality, acuity, refractive error, fundus characteristics, and coincident disease. Ninety-eight cases of identifiable hyaline bodies ([HB] group 1) were compared with 44 cases of pseudopapilledema without HB (group 2). The following results were notable: marked predominance of whites; one third in group 1 were unilateral, and 14% of all pseudopapilledema was unilateral; in only one eye did HB apparently account for diminished acuity; refractive error distribution paralleled that in the general population; anomalous vascular patterns occurred in 20% of group 1 and in 31% of group 2; pigment epithelial changes were found in 33% of group 1 and in 20% of group 2; and a statistically significant association was found with retinitis pigmentosa only. Analysis of field defects is the subject of a companion report.

Refractive error distribution in a profoundly retarded population.

The refractive errors distribution of 103 profoundly retarded individuals (10 of zero to 20) was determined. This distribution was skewed in the direction of myopia. Since no such data were available for any other profoundly retarded population, direct comparison with other studies was not possible. However, a significant difference in mean spherical equivalent was found between the profoundly retarded of this study and the combined severely and profoundly retarded of two earlier studies.

Myopia and eye enlargement after neonatal lid fusion in monkeys

THE aetiology of myopia has been studied mainly by investigating the distribution of refractive errors in human populations1. No clear conclusion has emerged, however, so the prevailing clinical attitude is that myopia can neither be prevented nor cured, but only corrected with appropriate lenses. The mechanism of myopia can be rationally analysed only if a suitable animal model is found for this refractive condition. In the literature, there are only two examples of experimental myopia. Levinsohn2 claimed that a high degree of myopia develops in young monkeys when the body is kept elevated above the head for long periods of time; his results, however, have been questioned3,4. Young5 induced myopia by exposing monkeys to a restricted visual space, but the refractive error thus obtained was relatively small. During investigations on monocular visual deprivation in monkeys6 it was noted that the eye in which the lids had been closed by suture at birth developed a high degree of myopia. We report here a study of the effects of neonatal lid fusion on the refractive state and anatomy of the macaque monkey eye.

Optometric data characteristics of male prison inmates.

Clinical optometric findings on 332 inmates, adult male felons, of a state prison referred to the consulting optometrist for routine services were subjected to statistical evaluation and comparison with data available from nonprison samples. No significant differences between the prison sample and variously available outside adult male samples were apparent in the frequency distribution of attainable acuities, spherical and cylindrical refractive errors, cylindical axis orientations, lateral and vertical phorias, and the bifocal additions at various age levels. This apparent lack of differences may reflect inadequacies of the comparisons to data not collected or presented in directly comparable manners. A significant frequency distribution difference was found in the interpupillary distances, with mean differences of 0.8 mm, 0.8 mm, and 2.1 mm less in each of three other adult male samples, respectively. No explanation is apparent. A number of statistical observations indicated that a relatively high proportion of inmates had not received or submitted to adequate optometric care prior to that obtained in the prison, that is, they had received significantly less care than comparably aged males who present themselves to public clinics and private practitioners for routine optometric services.

Refractive error distribution in New Zealand's Polynesian and European children.

Refractive error distribution in New Zealand's Polynesian and European children.

The distribution of refractive errors among children attending Lumbini Eye Institute, Nepal

Uncorrected refractive error is an important cause of childhood blindness and visual impairment. To describe the patterns of refractive errors among children attending the outpatient clinic at the Department of Pediatric Ophthalmology, Lumbini Eye Institute, Bhairahawa, Nepal. Records of 133 children with refractive errors aged 5 - 15 years from both the urban and rural areas of Nepal and the adjacent territory of India attending the hospital between September and November 2010 were examined for patterns of refractive errors. The SPSS statistical software was used to perform data analysis. The commonest type of refractive error among the children was astigmatism (47 %) followed by myopia (34 %) and hyperopia (15 %). The refractive error was more prevalent among children of both the genders of age group 11-15 years as compared to their younger counterparts (RR = 1.22, 95 % CI = 0.66 - 2.25). The refractive error was more common (70 %) in the rural than the urban children (26 %). The rural females had a higher (38 %) prevalence of myopia than urban females (18 %). Among the children with refractive errors, only 57 % were using spectacles at the initial presentation. Astigmatism is the commonest type of refractive error among the children of age 5 - 15 years followed by hypermetropia and myopia. Refractive error remains uncorrected in a significant number of children.

Study on the refractive errors of school going children of Pokhara city in Nepal

Refractive errors are the one of the most common visual disorders found worldwide in school going children and also it is one of the causes of blindness. It can easily be prevented, if timely proper measures are taken. In Kathmandu valley and Mechi Zone of Nepal, the distribution of refractive errors was found to be very high. No records are available from the Western part of Nepal. Considering the importance of the refractive errors the present study had been undertaken in Pokhara city. 964 subjects (474 boys, 490 girls) were selected between age groups 10 to 19 years from 6 schools representing different region of Pokhara. After Preliminary examination: on acuity of vision with Snellen's and Jaeger's charts, the subjects were referred to the Manipal Teaching Hospital, Pokhara for confirmation of the refractive errors. Sixty two schools children (6.43%), out of 964 had refractive errors. The myopia was found to be most common (4.05%). The refractive errors were found more in Private school children (9.29%) than Government school children (4.23%), which is statistically significant (P < 0.05). More boys (7.59%) were found to have suffered from refractive errors than girls (5.31%). Further, children with vegetarian diet (10.52%) had greater number of refractive errors than non-vegetarian diet children (6.17%). In the present study, percentage distribution of myopia was found to be higher (4.05%) than the hyperopia (1.24%) and astigmatism (1.14%). Interestingly, in the present study the refractive errors were found significantly higher in Private schools children than Government schools because the children who read in Private schools have higher socioeconomic status; spend more time in home work, watching Television and Computer as compared to government schools children. These near activities of the eyes causes stress on eyes of the children and might be one of the causes of developing myopia.

The distribution of refractive errors in monkeys

The refractive errors of 1000 rhesus monkeys ( Macaca mulatta ) and 100 pig-tailed monkeys ( Macaca nemestrina ) were determined by retinoscopy while the animals were under phencyclidine hydrochloride (Sernyl or Sernylan) anesthesia and cyclopentolate hydrochloride (Cyclogyl) cycloplegic. The rhesus population contained 642 females and 358 males and ranged in age from 8 months to 20 years. The pig-tailed monkeys comprised 69 females and 31 males ranging in age from 12 months to 15 years. Approximately one-third of each group were laboratory-born, with known ages. The ages of the other animals were estimated through the use of regression equations based on the age-weight relationship in the laboratory-born monkeys. Three hundred of the rhesus monkeys had been in captivity for less than 10 weeks. The refractive errors were analyzed and plotted by species, sex, age and by wild and laboratory groups. The mean and median refractive errors were found to be significantly more hypermetropic in the rhesus monkeys and among the younger age groups and wild animals and more myopic in the pig-tailed monkeys and among the older age groups and laboratory animals. The females showed a higher per cent of myopia in the 1- to 3-year-old groups, over all, and in the groups with myopia in excess of 6 diopters. The distribution of refractive errors in monkeys was compared with two distributions of refractive errors in humans. The monkey distribution fell midway between the human distributions and was similar in all essential characteristics.