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PubMed1999

Refractive errors in an urban population in Southern India: the Andhra Pradesh Eye Disease Study.

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.

Adolescent↗
PubMed2002

Refractive error in children in an urban population in New Delhi.

PURPOSE: To assess the prevalence of refractive error and related visual impairment in school-aged children in an urban population in New Delhi, India. METHODS: Random selection of geographically defined clusters was used to identify a sample of children 5 to 15 years of age. From December 2000 through March 2001, children in 22 selected clusters were enumerated through a door-to-door survey and examined at a local facility. The examination included visual acuity measurements, ocular motility evaluation, retinoscopy and autorefraction under cycloplegia, and examination of the anterior segment, media, and fundus. Myopia was defined as spherical equivalent refractive error of at least -0.50 D and hyperopia as +2.00 D or more. Children with reduced vision and a sample of those with normal vision underwent independent replicate examinations for quality assurance in four of the clusters. RESULTS: A total of 7008 children from 3426 households were enumerated, and 6447 (92.0%) examined. The prevalence of uncorrected, baseline (presenting), and best corrected visual acuity of 20/40 or worse in the better eye was 6.4%, 4.9%, and 0.81%, respectively. Refractive error was the cause in 81.7% of eyes with vision impairment, amblyopia in 4.4%, retinal disorders in 4.7%, other causes in 3.3%, and unexplained causes in the remaining 5.9%. There was an age-related shift in refractive error from hyperopia in young children (15.6% in 5-year-olds) toward myopia in older children (10.8% in 15-year-olds). Overall, hyperopia was present in 7.7% of children and myopia in 7.4%. Hyperopia was associated with female gender. Myopia was more common in children of fathers with higher levels of education. CONCLUSIONS: Reduced vision because of uncorrected refractive error is a major public health problem in urban school-aged children in India. Cost-effective strategies are needed to eliminate this easily treated cause of vision impairment.

Adolescent↗
PubMed1994

Refractive errors among engineering students in Norway.

This study reveals the prevalence of refractive errors in a group of young adults (mean age 20.6 years) exposed to high educational demands, including much reading. In all, 224 (117 females, 107 males) first-year engineering students were subjectively refracted. A prevalence of myopia of 46.9% (right eye), 49.1% (left eye) and 42.9% (both eyes), and a prevalence of hyperopia of 29.5% (right eye), 28.1% (left eye) and 23.2% (both eyes) was detected. The mean refractive error in the whole group was -0.6 +/- 2.2 D (right eye), -0.7 +/- 2.4 D (left eye) and -0.7 +/- 2.3 D (both eyes). As many as 56.4% (n = 57) of the myopic students had either no corrective lenses (11.9%, n = 12) or had their first corrective lenses prescribed at the age of 16 years or later (44.6%, n = 45). There was no significant difference in the prevalence of myopia between female and male students. No significant difference regarding body height was found among men in the different groups of refractive errors, but a significant difference was detected among women. We found no statistically significant relationship between intraocular pressure and any refractive error among men or women.

Adult↗
PubMed1990

Distribution of refractive errors in patients from Dominica, West Indies.

A total of 779 consecutive private patients requiring spectacles for correction of refractive errors were categorized according to age, sex, occupation and type of refractive error. Virtually all patients (97.1%) were black. The relationship between age, sex, occupation and refractive error was determined and showed that refractive errors were approximately equally distributed between the sexes, but myopia was more common among those with nearpoint occupations. Data also showed that more of the elderly were hyperopic than myopic in contrast to the younger patients who were more often myopic.

Adolescent↗
PubMed2000

AC/A ratio, age, and refractive error in children.

PURPOSE: To examine how the response AC/A ratio (the amount of accommodative convergence per unit of accommodative response) varies as a function of refractive error and age, to determine whether it is a risk factor for the onset of myopia, and to examine the relation between ocular structural features and the AC/A ratio. METHODS: Accommodation was stimulated by a letter target presented in a Badal system at 0.00, 2.25, and 4.37 D to 828 children aged 6 through 14 years in 1996. Of these, 726 had no myopia in 1996 and were available for examination the following year. Accommodative response and cycloplegic refractive error were measured by autorefraction and convergence by monitoring the relative movement of Purkinje images I and IV. Lens radii of curvature were measured by video phakometry, corneal radius of curvature by topography, and ocular axial dimensions by A-scan ultrasonography. RESULTS: Adjusted for age, the response AC/A ratio was highest in myopes (6.39 delta/D), intermediate in emmetropes (3.94 delta/D), and lowest in hyperopes (3.40 delta/D; P < 0.0001; two-way analysis of variance [ANOVA]). The stimulus AC/A ratio did not vary with refractive error. Adjusted for refractive error, the response AC/A ratio did not change as a function of age. In non-myopic children, having a response AC/A ratio of 5.84 delta/D or more elevated the risk of development of myopia within 1 year by 22.5 times (95% CI = 7.12-71.1). In a subsample of children without myopia who had refractive errors less than +0.75 D, having a response AC/A ratio of 5.84 delta/D or more elevated the risk of development of myopia within 1 year by 3.21 times (95% CI = 1.14-9.07). The AC/A ratio was associated with all measured ocular features except lens spherical volume. Only the negative correlations with refractive error and the shape of the crystalline lens (Gullstrand lens power) were significant in a multiple regression model (adjusted R2 = 0.16). CONCLUSIONS: An elevated response AC/A ratio was associated with myopia and was an important risk factor for its rapid onset. The association between higher AC/A ratios and flatter crystalline lens shapes, as well as other reported features of accommodation in myopia, may be explained by "pseudocycloplegia," which the authors define as tension on the crystalline lens that increases the level of effort needed to accommodate. Accommodative deficits in myopia may be the functional consequences of the underlying anatomy of the enlarged eye.

Accommodation, Ocular↗
PubMed2000

Refractive Error Study in Children: sampling and measurement methods for a multi-country survey.

PURPOSE: The Refractive Error Study in Children was designed to assess the prevalence of refractive error and vision impairment in children of different ethnic origins and cultural settings. METHODS: Population-based cross-sectional samples of children 5 to 15 years of age were obtained through cluster sampling. Presenting, uncorrected, and best-corrected visual acuity, along with refractive error under cycloplegia, were the main outcome measures. Amblyopia and other causes of uncorrectable vision impairment were determined. RESULTS: Study design and sample size calculations, survey enumeration and ophthalmic examination methods, quality assurance monitoring, and da ta analyses and statistical methods are described. CONCLUSIONS: The study design, sample size, and measurement methods ensure that the prevalence of age-specific and sex-specific refractive error can be estimated with reasonable accuracy in the target populations. With commonality of methods, a comparison of findings between studies in different ethnic origins and cultural settings is possible.

Adolescent↗
PubMed2002

Factors associated with undercorrected refractive errors in an older population: the Blue Mountains Eye Study.

AIMS: To identify characteristics of people with clinically relevant undercorrected refractive errors. METHODS: The Blue Mountains Eye Study was a population based survey of 3654 Australians aged 49-97 years. Examinations included a standardised refraction and measurement of presenting and best corrected visual acuity. Clinically relevant undercorrected refractive error was defined as improvement of >/=10 letters (2+ lines on the logMAR chart) in subjects with presenting acuity 6/9 or worse. Associations with a range of demographic and ocular variables were explored, adjusting for age and sex, presented as odds ratios (OR) with 95% confidence intervals (CI). RESULTS: Undercorrected refractive error was present in 814/3654 subjects (10.2%). Older age (p <0.001), hyperopia (OR 1.45, CI 1.15 to 1.83), longer interval from last eye examination (p <0.001), past occupation as tradesperson (OR 1.64, 1.13 to 3.29) or labourer (OR 2.00, CI 1.39 to 2.89), receipt of government pension (OR 1.47, CI 1.12 to 1.94), and living alone (OR 1.34, CI 1.05 to 1.72) were all associated with undercorrected refractive error. Past or current use of distance glasses (OR 0.25, CI 0.20 to 0.32) and driving (OR 0.67, CI 0.52 to 0.86) were associated with a lower prevalence. CONCLUSIONS: Increasing age and measures of socioeconomic disadvantage and isolation were found to predict undercorrected refractive error. Given the documented impacts from correctable visual impairment, these findings suggest a need to target education and eye care services.

Age Factors↗
PubMed1987

Relationship between refractive error and visual acuity in the Prospective Evaluation of Radial Keratotomy (PERK) Study.

As part of the Prospective Evaluation of Radial Keratotomy (PERK) study, we examined the relationship between post-operative refractive error and visual acuity without correction. We included 394 eyes (one eye per patient) with refractive errors ranging from -3.00 to +3.00 diopters one year after radial keratotomy. Within each 1-D range of the spherical equivalent of the refractive error, the visual acuity spanned five to ten Snellen lines. For visual acuities of 20/16 to 20/50, the refractive error spanned 3 to 5 D. Additionally, operated eyes had a better average uncorrected visual acuity than unoperated eyes with a similar refractive error. Within the narrow range of refraction between -2.00 and -2.50 D, the mean uncorrected visual acuity was 20/125 for 56 unoperated eyes and 20/63 for 29 operated eyes, a difference of three Snellen lines.

Adult↗
PubMed2001

Does cryotherapy affect refractive error? Results from treated versus control eyes in the cryotherapy for retinopathy of prematurity trial.

PURPOSE: To evaluate the effect of cryotherapy on refractive error status between ages 3 months and 10 years in children with birth weights of less than 1251 g in whom severe retinopathy of prematurity (ROP) developed in one or both eyes during the neonatal period. DESIGN: Randomized clinical trial. PARTICIPANTS: Two hundred ninety-one children in whom severe ROP developed during the neonatal period. INTERVENTION: Cryotherapy for ROP. MAIN OUTCOME MEASURES: Cycloplegic Refraction METHODS: The children underwent repeated follow-up eye examinations, including cycloplegic retinoscopy, between 3 months and 10 years after term due date. Refractive error data from all eyes that were randomized to cryotherapy were compared with data from all eyes that were randomized to serve as controls. Refractive error data were also compared for a subset of children who had both a treated and a control eye that could be refracted. RESULTS: At all ages, the proportion of treated eyes that were unable to be refracted because of retinal detachment, media opacity, or pupillary miosis was approximately half the proportion of the control eyes that were unable to be refracted. When data from all eyes that could be refracted were considered, the distribution of refractive errors between fewer than 8 diopters (D) of myopia and more than 8 D of hyperopia was similar for treated and control eyes at all ages. The proportion of eyes with 8 D or more of myopia was much higher in treated than in control eyes at all ages after 3 months. In the subset of children who had a treated eye and a control eye that could be refracted, distributions of refractive errors in treated versus control eyes were similar at most ages. CONCLUSIONS: In both treated and control eyes, there was an increase in the prevalence of high myopia between 3 and 12 months of age. Between 12 months and 10 years of age, there was little change in distribution of refractive error in treated or control eyes. The higher prevalence of myopia of 8 D or more in treated eyes, as compared with control eyes, may be the result of cryotherapy's preservation of retinal structure in eyes that, in the absence of cryotherapy, would have progressed to retinal detachment.

Astigmatism↗
PubMed1977

Refractive errors associated with hemangiomas of the eyelids and orbit in infancy.

Asymmetrical refractive errors, both astigmatic and myopic, were associated with infantile hemangiomas of the eyelids and orbit in 46% of 37 patients who had large lesions and upper eyelid involvement predisposing to the ammetropia. The axis of the astigmatic error related to the location of the eyelid hemangioma and correlated closely with keratometric measurements of corneal astigmatism. The refractive errors tended to be stable despite eventual resolution of the hemangiomas. Efforts to combat strabismic and refractive amblyopia were rewarding in many patients. A history of complete eyelid occlusion during part of the first year of life was associated with dense amblyopia and eccentric fixation in some patients, but in other patients this history was compatible with the eventual development of useful vision. Absence of an asymmetrical refractive error in patients with eyelid and orbital hemangiomas rendered the prognosis for vision good in involved eyes.

Astigmatism↗
PubMed1994

Screening of infants for significant refractive error using videorefraction.

Isotropic photorefraction has been suggested as a suitable method for screening infants for refractive error. Recently published data suggested that reasonable consistency with retinoscopy results might be achieved using cycloplegic videophotorefraction (VPR) for spherical refractive error but that results might be unreliable for astigmatic errors. Non-cycloplegic VPR did not appear to produce results consistent with retinoscopy. A practical idea of how many children might be identified using this technique and how many missed was needed by personnel designing screening projects. Hence the VPR was tested by screening a population of 247 infants for significant refractive error, and comparing the results with cycloplegic retinoscopy. Sensitivity and specificity scores were calculated for a range of test levels of ametropia. Without cycloplegia, sensitivity of VPR was poor. With cycloplegia the situation was much improved, with sensitivity for hyperopia +4.00 D or over of 83.3% and specificity of 90.6%. Sensitivity for astigmatism of 1 D or greater (84.6%) was high but specificity was poor (45.6%). Acceptable sensitivity was achieved for identifying children in this age group at risk of developing squint and amblyopia due to refractive error, providing cycloplegia was used.

Amblyopia↗
PubMed1987

The distribution of refractive errors in Nigeria.

A clinical study of the refractive errors of 349 females aged between 5 and 69 years and 473 males aged between 3 and 62 years was undertaken. This report describes the prevalence of the different types of refractive errors with regard to sex and age.

Adolescent↗
PubMed2002

[Assortative mating among individuals with refractive errors of the eye].

Negative assortative mating for refractive errors of the eyes of 1241 married couples was discovered in the urban region of the South Moravian region. 46 married couples were myopic, 55 hyperopic, 73 astigmatic, 175 had combinations of refractive errors, 261 were emetropic and 631 were mixed. Negative assortative mating is highly significant (chi-square P < or = 0.001). It is more significant for urban population. Positive selection for emetropic married couples plays more important role in urban peoples than in citizens.

Family Health↗
PubMed2000

Refractive error in cataract surgery after previous refractive surgery.

Bilateral cataract extraction with posterior chamber intraocular lens (IOL) implantation was performed in a patient after previous photorefractive keratectomy, radial keratotomy (RK) combined with astigmatic keratotomy, and retreatment of RK. Significant hyperopic error was observed after cataract surgery, and the IOLs were eventually exchanged in both eyes. A review of this case found that the refractive error was smaller when a refraction-derived keratometric value was selected for IOL power calculation. Nevertheless, hyperopic error still occurred.

Adult↗
PubMed1986

Refractive error and preferential looking visual acuity in human infants: a pilot study.

A clinical pilot study comparing refractive error and preferential looking (PL) visual acuity in infants 2 to 12 months of age is described. The PL visual acuity of 30 normal infants without significant visual disorders was assessed using the Acuity Card Procedure. Near retinoscopy was used to determine refractive error. Infants of this sample had monocular PL visual acuities similar to those established by McDonald et al. in a laboratory setting. Statistical analysis of the data for this sample of infants showed that refractive error did not change systematically from 2 to 12 months of age. We have found that results obtained with the Acuity Card Procedure in a clinical setting agree with infant visual acuity as described in the research literature. Refractive error did not correlate with changes in PL visual acuity in infants 2 to 12 months of age.

Humans↗
PubMed2001

Axial length and refractive error in X-linked retinoschisis.

PURPOSE: To examine the relationship between axial length and refractive error in patients with X-linked retinoschisis. DESIGN: To determine whether the hypermetropia frequently found in patients with X-linked retinoschisis is axial hypermetropia. METHODS: The axial length and refractive error were measured in 29 right eyes of 29 patients. The patients were divided into two groups: a juvenile group with ages <13 years (12 eyes) and an adult group with ages > or =13 years (17 eyes). The axial length of the right eye of 30 adult men without eye diseases whose refractive error ranged from +/- 1.0 diopter served as controls. RESULTS: In the adult patient group, the refractive error was significantly more hypermetropic and the axial length was significantly shorter than was the normal adult group (P <.001). CONCLUSION: These results strongly suggest that the hypermetropia in patients with X-linked retinoschisis is axial hypermetropia.

Adolescent↗
PubMed1997

Refractive errors in children born before 32 weeks gestation.

PURPOSE: To document the refractive errors in a cohort of children born before 32 weeks gestation. METHODS: All children born before 32 weeks gestation between 1 January 1990 and 31 December 1991 to mothers resident in the Northern Region of the National Health Service were examined at 2 years old (n = 558). RESULTS: Stage 3 or worse retinopathy of prematurity (ROP) was associated with myopia. In those not developing stage 3 or worse ROP, the refractive errors were myopia in 1.5%, hypermetropia > 4 dioptres (D) in 5.4%, anisometropia > 1 D in 1.1% and astigmatism > 1.25 D in 5.7%. CONCLUSION: The incidence of refractive errors in those not developing stage 3 or worse ROP was similar to that in the general population.

Acute Disease↗
PubMed1993

Effect of uncorrected refractive errors upon central visual field testing.

An investigation of the effects of uncorrected refractive errors upon a central visual field examination has been made with a view to establishing what the likely effects would be of omitting a refractive correction when screening the visual field with a threshold related, supra-threshold strategy on the Henson CFA3000. The results indicate that, while a linear relationship exists between the extent of threshold elevation and the product of residual refractive error and pupil size, the scatter in the results means that accurate predictions cannot be made in individual cases. The threshold elevation was found to be independent of eccentricity (within the central 21 degrees from fixation) and did not increase the variability of results. These last two findings indicate that uncorrected refractive errors are unlikely to affect the sensitivity of the threshold related, supra-threshold strategy to localized visual field defects.

Adult↗