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PubMed2003

Refractive error and visual impairment in African children in South Africa.

PURPOSE: To assess the prevalence of refractive error and visual impairment in school-aged African children in South Africa. METHODS: Random selection of geographically defined clusters was used to identify a sample of children 5 to 15 years of age in the Durban area. From January to August 2002, children in 35 clusters were enumerated through a door-to-door survey and examined in temporary facilities. The examination included visual acuity measurements, ocular motility evaluation, retinoscopy and autorefraction under cycloplegia, and examination of the anterior segment, media, and fundus. In nine clusters, children with reduced vision and a sample of those with normal vision underwent independent replicate examinations for quality assurance. RESULTS: A total of 5599 children living in 2712 households were enumerated, and 4890 (87.3%) were examined. The prevalence of uncorrected, presenting, and best-corrected visual acuity of 20/40 or worse in the better eye was 1.4%, 1.2%, and 0.32%, respectively. Refractive error was the cause in 63.6% of the 191 eyes with reduced vision, amblyopia in 7.3%, retinal disorders in 9.9%, corneal opacity in 3.7%, other causes in 3.1%, and unexplained causes in the remaining 12.0%. Exterior and anterior segment abnormalities were observed in 528 (10.8%) children, mainly corneal and conjunctival. Myopia (at least -0.50 D) in one or both eyes was present in 2.9% of children when measured with retinoscopy and in 4.0% measured with autorefraction. Beginning with an upward trend at age 14, myopia prevalence with autorefraction reached 9.6% at age 15. Myopia was also associated with increased parental education. Hyperopia (+2.00 D or more) in at least one eye was present in 1.8% of children when measured with retinoscopy and in 2.6% measured with autorefraction, with no significant predictors of hyperopia risk. CONCLUSIONS: The prevalence of reduced vision is low in school-age African children, most of it because of uncorrected refractive error. The high prevalence of corneal and other anterior segment abnormalities is a reflection of the inadequacy of primary eye care services in this area.

Adolescent↗
PubMed2006

Correlations in refractive errors between siblings in the Singapore Cohort Study of Risk factors for Myopia.

BACKGROUND: The prevalence of myopia in parts of South East Asia has risen dramatically over the past 1-2 generations, suggesting that environmental factors may be particularly important determinants of refractive development in these populations. AIM: To assess the contribution of familial factors (shared genes and/or shared family environment) to refractive error and ocular component dimensions of school-aged children in Singapore. METHODS: Data were available for 315 children who had one or more siblings also participating in the Singapore Cohort Study of the Risk factors for Myopia (SCORM). Refractive error and ocular biometric parameters were measured under cycloplegia at baseline when children were 7-9 years, and at yearly follow-up sessions for the next 3 years, using consistent clinical procedures. The time children spent performing a variety of nearwork-related tasks was obtained from questionnaires. Familial influences were assessed by calculating between-sibling correlations. RESULTS: After adjusting for age and sex, the between-sibling correlation in refractive error was 0.447 (95% CI 0.314 to 0.564), suggesting that familial factors account for 63-100% of the variation in the cohort. The between-sibling correlation for 1-year change in refractive error was similarly high, at 0.420 (95% CI 0.282 to 0.543). All ocular component dimensions were correlated significantly between siblings, especially for corneal curvature and vitreous chamber depth--the major structural determinants of refraction. The amount of time siblings spent engaged in nearwork tasks (reading, watching TV, playing video games, computing) and in outdoor activities was also highly correlated between siblings (p<0.001). CONCLUSION: Shared genes and/or shared environment are important factors in the refractive development of children in Singapore. Because the time spent in nearwork tasks is highly correlated between siblings, epidemiological studies will benefit from precise, quantitative measures of refractive error in parents and more distant relatives in order to begin to dissociate genetic and environmental sources of variation.

Biometry↗
PubMed1999

[Predicted versus actual postoperative refractive error after simultaneous vitrectomy and cataract surgery].

PURPOSE: We compared the spread between predicted and postoperative actual refractive errors after simultaneous vitrectomy, phacoemulsification, aspiration, and acryl lens insertion and after cataract surgery alone. METHODS: Cataract surgery and vitrectomy (combined surgery group) were performed in 185 eyes, and cataract surgery only (cataract surgery group) in 63 eyes. Vitrectomy was needed for diabetic retinopathy in 104 eyes, macular hole in 26 eyes, rhegmatogenous retinal detachment in 25 eyes, and other conditions in 30 eyes. RESULTS: The spread between predicted and actual refractive errors were +0.19 +/- 1.24 D (mean +/- standard deviation) in the combined surgery group and +0.91 +/- 1.40 D in the cataract surgery group. Gas tamponade in the combined surgery group increased the myopic change more than anything else. CONCLUSION: Actual refractive errors in the combined surgery group were found to shift to myopia more than in the cataract surgery group. Gas tamponade was considered to press the intraocular lens forward in the combined surgery group.

Adult↗
PubMed2003

Measurement of refractive errors in young myopes using the COAS Shack-Hartmann aberrometer.

PURPOSE: To evaluate the Complete Ophthalmic Analysis System (COAS; WaveFront Science) for accuracy, repeatability, and instrument myopia when measuring myopic refractive errors. METHODS: We measured the refractive errors of 20 myopic subjects (+0.25 to -10 D sphere; 0 to -1.75 D cylinder) with a COAS, a phoropter, and a Nidek ARK-2000 autorefractor. Measurements were made for right and left eyes, with and without cycloplegia, and data were analyzed for large and small pupils. We used the phoropter refraction as our estimate of the true refractive error, so accuracy was defined as the difference between phoropter refraction and that of the COAS and autorefractor. Differences and means were computed using power vectors, and accuracy was summarized in terms of mean vector and mean spherocylindrical power errors. To assess repeatability, we computed the mean vector deviation for each of five measurements from the mean power vector and computed a coefficient of repeatability. Instrument myopia was defined as the difference between cycloplegic and noncycloplegic refractions for the same eyes. RESULTS: Without cycloplegia, both the COAS and autorefractor had mean power vector errors of 0.3 to 0.4 D. Cycloplegia improved autorefractor accuracy by 0.1 D, but COAS accuracy remained the same. For large pupils, COAS accuracy was best when Zernike mode Z4(0) (primary spherical aberration) was included in the computation of sphere power. COAS repeatability was slightly better than autorefraction repeatability. Mean instrument myopia for the COAS was not significantly different from zero. CONCLUSIONS: When measuring myopes, COAS accuracy, repeatability, and instrument myopia were similar to those of the autorefractor. Error margins for both were better than the accuracy of subjective refraction. We conclude that in addition to its capability to measure higher-order aberrations, the COAS can be used as a reliable, accurate autorefractor.

Adolescent↗
PubMed2002

[Summary of the practice guideline 'Refraction errors' from the Dutch College of General Practitioners].

The practice guideline 'Refraction errors' from the Dutch College of General Practitioners describes the examinations that need to be carried out in patients complaining about a gradual loss of vision. A measurement of vision by means of a Snellen chart is insufficient to determine if the condition is caused by a refraction error or if other pathology of the eye such as cataract, glaucoma or retinopathy is involved. It is therefore recommended that the vision should also be measured with a simple device containing spherical lenses of +0.5 and -0.5 dioptre, so-called diagnostic refraction. Improvement of vision with the negative lens indicates myopia. Improvement or at least a stable vision with the positive lens makes hyperopia very likely. Diagnostic refraction, which can be used in patients of six years and older, enables the general practitioner to distinguish between patients needing glasses or contact lenses, and patients requiring referral to an ophthalmologist.

Diagnosis, Differential↗
PubMed1984

Refractive errors in a Finnish rural population.

Refractive errors in 611 persons living in a rural area were examined. Males numbered 281 and females 330. The age range was from 6 to 85 years. In 73 (11.9%) persons the refraction was myopic (SER less than or equal to 0.5 D) and in 173 (28.3%) hyperopic (SER greater than or equal to + 2 D). Myopia was most frequently detected in persons aged 21-30 years (22.6%), and the proportion of myopia decreased towards both extremes of age. In all age groups females were more myopic than males. In persons aged 21-60 years the most educated proved to have more myopia and less hyperopia than those with less education. In 158 (25.9%) of the eyes, astigmatism was detectable. The degree of astigmatism changed little with advancing age and was independent of sex. In myopic eyes the range of astigmatic error was wider than in hyperopic eyes. The axis of + cylinders was in hyperopic eyes mostly horizontal and in myopic eyes vertical. Anisometropia of 1.25-2.0 D was detected in 24 (4.0%) persons and in 19 (3.1%) persons it was over 2 D.

Adolescent↗
PubMed1988

Refractive error, IQ and reading ability: a longitudinal study from age seven to 11.

Children from a population sample whose cycloplegic refractive errors included myopia, pre-myopia and hypermetropia were compared on measures of IQ and reading with a group of children without significance refractive errors. At age 11 both those with myopia and with pre-myopia had increased verbal and performance IQ, while those with hypermetropia had slightly reduced verbal and performance IQ, in comparison with the children without refractive errors. The differences in verbal IQ were not attributable simply to earlier differences, but the differences in performance IQ were attributable to earlier differences. No significant differences in reading scores were found at either age. It is concluded that differing abilities of myopic and other children at age 11 are not fully explained by differences in family background or in pre-existing ability.

Child↗
PubMed1984

Screening for refractive errors in 6-9 month old infants by photorefraction.

The method of isotropic photorefraction has been used in a trial of refractive screening of 6-9 month old infants. Data are presented on the calibration of the method against retinoscopic measurements and its reliability. In photorefractive screening of 1096 infants under cyclopentolate cycloplegia 5% were found to be hypermetropic (over +3.5 D), 4.5% myopic, and 1.3% anisometropic (over 1 D). These refractive errors were confirmed on retinoscopic follow-up (with the exception of a few anisometropes). Follow-up of controls shows that one small refractive error was missed in 52 infants. We conclude that photorefraction is a valid and practical screening technique. Longitudinal study of infants with refractive errors will assess the value of early detection, in particular for prediction and prevention of strabismus.

Adult↗
PubMed1983

Variations of refractive error during the first year of contact lens wear.

The variations of refractive errors during both hard, hydrophilic and silicone lens wear were significantly correlated in the 2 eyes of each individual. In each lens group the mean changes of spherical and cylindrical refractive errors were small (-0.458D-+0.250D and -0.325D-+0.056D, respectively). Considerable individual refractive changes occurred (spherical change: -3.0D-+1.5D, cylindrical change: -2.5D-+1.0D). However, only 2 subjects noticed spectacle blur and a normal visual acuity was always obtained by spectacle refraction immediately after lens removal. This indicated that clinically significant distortion of the central cornea did not take place. Hydrophilic lens wearers showed an increasing myopia during lens wear. Otherwise the refractive changes were not significantly influenced by the duration of lens wear. Refractive changes appeared to be significantly correlated to changes of the central anterior corneal curvature, the ratio of dioptric changes being about 1:1.

Adolescent↗
PubMed1999

Studies of intrastromal corneal ring segments for the correction of low to moderate myopic refractive errors.

PURPOSE: Intrastromal corneal ring segments (ICRS) were investigated for safety and reliability in the correction of low to moderate myopic refractive errors. METHODS: Initially, 74 patients with spherical equivalent refractive errors between -1.00 and -4.25 diopters (D) received the ICRS in 1 eye. After 6 months, 51 of these patients received the ICRS in the contralateral eye. The total number of eyes investigated was 125. The outcome measures were uncorrected and best-corrected visual acuity, predictability and stability of the refraction, refractive astigmatism, contrast sensitivity, and endothelial cell morphology. RESULTS: The 89 eyes with 12-month follow-up showed significant improvement with uncorrected visual acuities of 20/16 or better in 37%, 20/20 or better in 62%, and 20/40 or better in 97%. Cycloplegic refraction spherical equivalents showed that 68% of the eyes were within +/- 0.50 D and 90% within +/- 1.00 D of the intended correction. Refractive stability was present by 3 months after the surgery. Only 1 patients had a loss greater than 2 lines or 10 letters of best spectacle-corrected visual acuity, but the patient's acuity was 20/20. Refractive cylinder, contrast sensitivity, and endothelial cell morphology were not adversely affected. The ICRS was removed from the eyes of 6 patients. Three removals were prompted by glare and double images occurring at night; 3 were for nonmedical reasons. All patients returned to within +/- 1.00 D of their preoperative refractive spherical equivalent, and no patients lost more than 1 line of best corrected visual acuity by 3 months after ICRS removal. CONCLUSION: The ICRS safely and reliably corrects myopic refractive errors between -1.00 and -4.50 D.

Adult↗
PubMed1981

Effect of refractive error on the risk of ocular hypertension and open angle glaucoma.

From a case-control study of out-patients attending an ophthalmic clinic no relationship (relative risk = 1) was found between refractive error and ocular tension. The deconfounded effect of refractive error on open angle glaucoma (field loss) increased at higher levels of myopia (relative risk = 1.18; refractive error -0.2) The combined effects of myopia and severe ocular hypertension were found to be synergistic (interactive risk ratio = 2.2).

Glaucoma, Open-Angle↗
PubMed1999

Pediatric photoscreening for strabismus and refractive errors in a high-risk population.

OBJECTIVE: To determine the accuracy of the MTI Photoscreener in detecting strabismus and refractive errors in children. PARTICIPANTS: One hundred children underwent MTI photoscreening followed by complete ophthalmologic examination. Six observers graded the photographs for strabismus, according to the location of the corneal light reflexes, and for refractive error, according to the size and location of the light crescent. RESULTS: The sensitivity of the MTI Photoscreener in detecting any amblyogenic factor was 80% to 91%, with a specificity of 20% to 67%. The sensitivity and specificity for particular amblyogenic factors varied widely among observers. The ranges were as follows: strabismus, sensitivity = 23% to 50%, specificity = 76% to 96%; myopia, sensitivity = 89%, specificity = 48% to 76%; hyperopia, sensitivity = 20% to 80%, specificity = 88% to 96%; and astigmatism, sensitivity = 46% to 77%, specificity = 79% to 89%. CONCLUSIONS: These results suggest caution in relying on photoscreening to detect strabismus and refractive errors in children.

Child↗
PubMed1998

Complex refractive errors in pediatric patients: cause, management, and criteria for success.

BACKGROUND: Uncorrected refractive error in children is an important contributor to permanent neurological visual impairment (amblyopia). Spectacles are often inadequate for certain refractive errors that occur in the pediatric population. Therefore, the purpose of this paper is to present the diagnostic and therapeutic considerations of infants and children referred to a hospital specialty contact lens practice during a 30-month period. METHODS: A retrospective cohort design was used to study patients 12 years or younger referred to a hospital-based contact lens service and cared for by the author. Sixty patients were first examined during the enrollment period. Follow-up data were collected after a period of no less than 3 years from the initial visit. Success with the prescribed therapy was assessed by comparing the final method of optical correction with that prescribed at the initial presentation. RESULTS: Aphakia and trauma were the two most common causes for referral, representing 57% of the patients younger than age 12. Contact lenses were prescribed for 51 of the 60 patients (85%) at presentation. Seventy-five percent of patients with unilateral aphakia attributable to congenital cataract were wearing a contact lens at the most recent follow-up examination. This was reduced to 60% with aphakia after trauma and just 50% with bilateral aphakia. The frequency of a visual acuity of 20/40 or better was 67% for bilateral aphakia, 47% after trauma with aphakia, and 25% for unilateral aphakia. CONCLUSIONS: The results presented here suggest that patients with unilateral aphakia attributable to congenital cataract have the most consistent contact lens wear, followed by patients with unilateral aphakia attributable to trauma. Patients with bilateral aphakia were more likely to have changed to spectacle lens wear. Patients wearing contact lenses at the most recent follow-up examination were more likely to have good visual acuity.

Aphakia, Postcataract↗
PubMed2003

Refractive errors in an elderly Chinese population in Taiwan: the Shihpai Eye Study.

PURPOSE: Few epidemiologic data are available on refractive status in elderly Asians. The purpose of the study was to determine prevalence and risk factors associated with refractive errors in a metropolitan elderly Chinese population in Taiwan. METHODS: A population-based survey was conducted in the Shihpai district of Taipei, Taiwan. A total of 2045 residents aged 65 years or more were randomly selected and invited to complete a comprehensive questionnaire and undertake a detailed ocular examination, including best corrected visual acuity and measurements of refractive error, using autorefraction. Of the subjects, 1361 (66.6%) participated in the ocular examination. Spherical equivalent (SE) was calculated in diopters (D), and data from right eyes were reported. RESULTS: The age- and sex-adjusted prevalence rates were determined for myopia (SE<-0.5 D, 19.4%; SE<-1.0 D, 14.5%), high myopia (SE<-6.0 D, 2.4%), hyperopia (SE>+0.5 D, 59.0%; SE>+1.0 D, 44.2%), astigmatism (cylinder<-0.5 D, 74.0%; cylinder<-1.0 D, 45.3%), and anisometropia (SE difference between right and left eyes>0.5 D, 45.2%; SE difference>1.0 D, 21.8%). The prevalence of myopia, astigmatism, and anisometropia significantly increased with age (all P<0.01). The prevalence of hyperopia tended to decrease with age. There was no gender difference in prevalence rates in any type of refractive error, except that women had a higher rate of hyperopia (SE>+1.0 D) than men (P=0.004). Multivariate regression analysis showed that myopia was weakly associated with higher educational level. The severity of lens nuclear opacity was positively associated with the rates of myopia and negatively associated with the rates of hyperopia. CONCLUSIONS: The prevalence of myopia in this elderly Chinese population is not much higher than in similarly aged elderly white populations, compared with a much greater difference in prevalence among younger Chinese versus white people. This suggests that changing environmental factors may account for the increased prevalence of myopia in younger cohorts of Chinese.

Age Distribution↗
PubMed2004

Longitudinal changes in the refractive errors of children with tears in Descemet's membrane following forceps injuries.

BACKGROUND: Eyes with tears in Descemet's membrane secondary to forceps injuries frequently develop myopic astigmatism. Little is known regarding the longitudinal changes in the refractive errors of these eyes. METHODS: We performed a retrospective review of two children with tears in Descemet's membrane following forceps injuries to their left eyes. The refractive errors were followed longitudinally. RESULTS: Both patients developed myopic astigmatism in their affected eye and received optical correction and occlusion therapy. In both cases there was reduction in the myopic refractive error during early childhood. While the astigmatic refractive error was stable in one patient it decreased in the second patient. CONCLUSION: Myopia decreased in two children with myopic astigmatism secondary to tears in Descemet's membrane. Myopia in children with tears in Desemet's membrane is likely due to deformation of the cornea rather than form-deprivation.

Anisometropia↗
PubMed2005

Family history of myopia is not related to the final amount of refractive error in low and moderate myopia.

BACKGROUND: Previous research has found an association between family history and presence of myopia. It is possible that family history also could be related to the final amount of refractive error developed. If that were true, then family history of myopia could have predictive value for the amount of refractive error a child or young adult would develop after first lens prescription. METHODS: Consecutive myopic adult outpatients were enrolled during the year 2003. They received a refractive examination and a questionnaire concerning age of onset of lens use, academic achievement, and parental history of myopia. RESULTS: In the group of 271 mild and moderate myopes (myopia lower than -6 D) there were 157 subjects with at least one myopic parent and 114 subjects without family history. The presence or absence of a family history of myopia was not associated with either the final myopic refractive error (-3.2 +/- 1.5 D and -2.9 +/- 1.3 D, respectively, P = 0.08) or the age of onset of lens use (17.0 +/- 6.2 years vs 18.1 +/- 6.7 years, respectively, P = 0.15). CONCLUSIONS: In the present retrospective study of a clinical sample of mild and moderate myopic subjects, family history of myopia did not show predictive value for either the age of first prescription, or the final refractive error developed in adulthood.

Adult↗
PubMed1995

Emmetropisation in human infancy: rate of change is related to initial refractive error.

Animal studies show that the rate of recovery from experimentally induced refractive errors is related to the level of ametropia induced. The present study examined the rate of emmetropisation occurring in a sample of 22 human infants refracted by near retinoscopy during the first six months of life and then again between 12 and 17 months old. None of the subjects were myopic. Regression analysis revealed that emmetropisation occurred more rapidly in the presence of high refractive errors (P < 0.005 and P = 0.001 for hyperopia and astigmatism respectively). These data confirm the findings of the animal studies and suggest that non-reducing hyperopia and astigmatism in the second year of life may require correction.

Aging↗
PubMed2000

The influence of age, gender, refractive error, and optic disc size on the optic disc configuration in Japanese normal eyes.

PURPOSE: To investigate the influence of age, gender, refractive error, and optic disc size on optic disc configuration in Japanese normal eyes. METHODS: Ninety-two eyes from 92 visually normal Japanese subjects (mean refractive error+/-SD: -1.26+/-2.25 D, range -8 D to +3 D) were examined using a confocal scanning laser tomograph, TopSS. The following disc parameters were investigated: disc size, total or quadrant C/D area ratio and neuroretinal rim area, half-depth area, volume below, and average cup depth. RESULTS: The disc diameter ( mean+/-SD: 1.84+/-0.16 mm) and disc size showed highly significant correlations with the C/D ratio (p<0.001) and the neuroretinal rim area (p<0.001). No other correlation was observed. CONCLUSION: These results indicate that the optic disc diameter and disc size have higher correlations with the optic disc configuration than age, gender, and refractive error in Japanese. These results are similar to those data reported for eyes of Caucasians or Afro Americans, and should be considered when optic discs are evaluated.

Adult↗