Prevalence, Associated Factors, and Inter-Eye Differences of Refractive Errors in a Population-Based Japanese Cohort: The Tohoku Medical Megabank Eye Study

PURPOSE

To investigate the prevalence, associated factors, and inter-eye differences of myopia and astigmatism in an adult Japanese population-based cohort.

METHODS

A total of 4282 participants from the Tohoku Medical Megabank Organization Eye Study (ToMMo Eye Study) underwent comprehensive ocular examinations as well as extensive physiological tests and a lifestyle questionnaire. The spherical equivalent (SE) and cylinder power were obtained as refractive parameters. The age- and gender-stratified prevalences of high myopia (SE < -5D), myopia (SE < -0.5D), hyperopia (SE > 0.5D), astigmatism (cylinder power < -0.5D), and anisometropia (SE difference >1D) were calculated. Multivariable analyses were performed to identify associated factors for refractive error (RE). Distribution and associated factors of the inter-eye difference in RE were also investigated.

RESULTS

The age-adjusted prevalence of high myopia, myopia, hyperopia, astigmatism, and anisometropia was 15.9%, 63.5%, 14.7%, 51.1%, and 14.7%, respectively. Both myopia and high myopia were more prevalent in the younger age group, while astigmatism was more prevalent in the older age group. Age, education, blood pressure, intraocular pressure, and corneal thickness are significantly associated with myopic refraction. Age, gender, intraocular pressure, and corneal thickness are correlated with astigmatism. Older age was associated with against-the-rule astigmatism. Older age, myopia, and longer education showed a significant correlation with large inter-eye differences in SERE.

CONCLUSIONS

This study demonstrated the high prevalence of myopia in young Japanese, which may be caused by a generational shift. This study also confirmed the influence of age and education on both the prevalence and inter-eye differences of RE.

Anisometropia and its association with refraction development in highly myopic children

CLINICAL RELEVANCE

Anisometropia can affect visual development in children. Investigations of anisometropia in high myopes would explore potential causes related to anisometropia, highlighting the management of anisometropia in high myopia.

BACKGROUND

The prevalence of anisometropia ranged from 0.6% to 4.3% in general paediatric population and from 7% to 14% in myopes. Anisometropia is regarded as an associated factor for myopia development, while myopia progression is a stimulus driving anisometropic development. The purpose of this study was to investigate the prevalence of anisometropia and its association with refraction development in Chinese children with high myopia.

METHODS

In the cohort study, a total of 1,577 highly myopic (spherical equivalent ≤-5.0D) children aged 4-18 years were included. Refractive parameters (dioptre of sphere, dioptre of cylinder, corneal curvature radius, and axial length) of both eyes were measured after cycloplegia. The prevalence and degree of anisometropia were compared among refractive groups (non-parametric tests or chi-square tests), and regression analyses were used to determine associated factors of anisometropia. The statistical significance was set to P < 0.05 (two-tailed).

RESULTS

In highly myopic children with a mean (standard deviation) age of 13.06 (2.80) years, the proportions of spherical equivalent anisometropia, cylindrical anisometropia and spherical anisometropia ≥1.00 D were 34.5%, 21.9% and 39.9%, respectively. There was more spherical equivalent anisometropia associated with more severe astigmatism (P for trend <0.001). In the multivariate regression analysis, more spherical equivalent anisometropia, cylindrical anisometropia and spherical anisometropia were associated with higher degrees of astigmatism (standard beta = -0.175, -0.148 and -0.191, respectively). More spherical anisometropia was associated with better spherical power (standard beta = 0.116).

CONCLUSION

The proportion of anisometropia in highly myopic children was high, compared with previously reported general population, and more severe anisometropia was associated with higher degree of cylindrical power, but not spherical power.

Risk factors for anisometropia in schoolchildren: A population-based, longitudinal cohort study

PURPOSE

To investigate the incidence rate and risk factors for anisometropia among young schoolchildren.

METHODS

A population-based cohort study, the Myopia Investigation Study in Taipei, was conducted in primary schools in Taipei City. Children were recruited for biannual comprehensive eye examinations over 2 years. Cycloplegic autorefraction and slit lamp examinations were performed biannually. Data on demographic information, parental history, lifestyle and near-work activities were collected using parent-administered questionnaires at the first and final visits. Anisometropia was defined as ≥1 D difference in the spherical equivalent (SE) refractive error.

RESULTS

A total of 7035 8-year-old children completed the 2-year follow-up evaluations. The average annual incidence of anisometropia was 3.8%. Multivariable logistic regression analysis revealed that baseline SE (odds ratio [OR]: 0.87 95% CI: 0.80-0.95) and female sex (OR: 1.24, 95% confidence interval [CI]: 1.02-1.50) were significantly associated with incident anisometropia. Among lifestyle risk factors, spending <1 h per day in after-school outdoor activities on weekdays (OR: 1.38, 95% CI: 1.08-1.76) and performing near work at a distance <30 cm (OR: 1.33, 95% CI: 1.08-1.64) were significantly associated with an increased risk of incident anisometropia. In the multiple linear regression analysis, the inter-eye difference in SE increased significantly in children performing near work at distances <30 cm (adjusted β = 0.03; p = 0.02).

CONCLUSIONS

This study indicated the annual incidence of anisometropia in Taiwanese schoolchildren. Less time spent outdoors and shorter eye-to-object distances during near work increased the risk of incident anisometropia.

Anisometropia Profile in Elderly Population: Tehran Geriatric Eye Study

PURPOSE

To investigate the distribution and prevalence of anisometropia according to age, gender and ocular biometry in a geriatric population in Tehran, Iran.

METHODS

The present study was conducted on the geriatric population aged above 60 years. The study participants were selected using stratified random cluster sampling. The uncorrected and best-corrected visual acuity, dry objective (ARK510A, Nidek Co. 42 LTD, Aichi, Japan) and subjective refraction and ocular biometry (IOL Master 500; Carl Zeiss Meditec, Jena, Germany) were recorded for each patient. The magnitude and prevalence of anisometropia were evaluated in association with influential factors in cut-points of 0.50, 1.00, 1.50 and 2.00 diopter (D).

RESULTS

The mean age of participants (3237 individuals, 54% were female) was 68.19 ± 6.48 (range: 60-97) years. The mean anisometropia in the whole sample was 0.82 D (95% CI: 0.76 - 0.88 D), which increased from 0.62 D (in those aged 60-64 years old) to 1.36 D (in those above 80 years). The prevalence of anisometropia >1 D in total population, males, and females were 23.81%, 24.9%, and 22.76%, respectively. The odds ratio of anisometropia was higher in cases with cataracts, myopia compared to emmetropia, keratometry asymmetry, axial length asymmetry (P = .001), and corneal diameter asymmetry (all others, P < .001).

CONCLUSION

The results of the present study show a high prevalence of anisometropia in elderly population, which was related to refractive error, cataract, age, gender, and ocular biometry asymmetry.

Frequency of anisometropia in children and adolescents

Background: Our objective was to estimate the frequency of anisometropia at various educational stages, from pre-school to 9th school year, studying its association with gender, study cycle and area of residence. Methods: 749 children and adolescents (from 3 to 16 years old) participated in this study, 46.7% girls and 42.7% living in a rural environment. The refraction was performed with a paediatric, open field autorefractometer (PlusOptix), without cycloplegic and under binocular conditions. Results: The frequency rate of anisometropia in the studied sample was 6.1%, varying from 2.9% in pre-school education to 9.4% in the 3rd study cycle. Myopic anisometropia was the most frequent and hyperopic and astigmatic anisometropia showed identical proportions of occurrence. No statistical evidence was found to state that the occurrence of anisometropia differs between genders or between areas of residence. Regarding the school cycle, a significant association was found with spherical equivalent anisometropia, with an increase in its frequency with school progress (p=0,012), with myopic anisometropia being the main contributor to this variation. Conclusions: The increase in workload for near tasks has been identified as a risk factor for the increase in myopia. This fact may be related to the increase in anisometropia with the educational stage, found in this study. The high rate of anisometropia found in adolescents (9.4%) as well as the progressive increase in this rate throughout school progress (from 2.9% to 9.4%) suggests the need to extend the detection strategies of this condition to beyond childhood.

Prevalence of anisometropia in children and adolescents

Background: This research was developed to study the epidemiology of anisometropia. It aims to estimate the prevalence of anisometropia in Portuguese children and adolescents at various educational stages, studying its association with sociodemographic variables. Methods: Observational cross sectional study envolving 749 children and adolescents (from 3 to 16 years old) from the central region of Portugal. The refraction was performed with a paediatric, open field auto refractometer (PlusOptix), without cycloplegia and under binocular conditions, to determine the rate of anisometropia and its association with gender, study cycle and area of residence. Results: The prevalence of anisometropia in the studied sample was 6.1%, varying from 2.9% in pre-school education to 9.4% in the 3rd study cycle. Myopic anisometropia was the most frequent and hyperopic and astigmatic anisometropia showed identical proportions of occurrence. No statistical differences were found between genders or between areas of residence regarding the rate of anisometropia. Regarding spherical equivalent anisometropia, there was a pattern of variation that increased with the cycle of studies (× ²₍₃₎= 10.918; p = 0.012), with myopic anisometropia being the main contributor to this variation. Conclusions: An increase in anisometropia with the educational stage, was found in this study. The high rate of anisometropia found in adolescents (9.4%) as well as the progressive increase in this rate throughout school progress (from 2.9% to 9.4%) suggests the need to extend the detection strategies of this condition beyond childhood.

Late Ophthalmologic Referral of Anisometropic Amblyopia: A Retrospective Study of Different Amblyopia Subtypes

INTRODUCTION

Amblyopia requires a timely diagnosis and treatment to attain maximum vision recovery. Specialty literature is lacking on how early amblyopia is referred. We aimed to understand if there are mean age differences at first referral for ophthalmologic tertiary center consultation among non-amblyopic and different types of amblyopia, in a context of lack of population screening.

MATERIAL AND METHODS

In this retrospective model, the sample corresponded to all children born in Braga Hospital during 1997 - 2012 (3 - 18 years-old), with an ophthalmologic consultation in 2014. Data was collected from the clinical records and children were divided in a non-amblyopic versus amblyopic group. The amblyopic group was subdivided in strabismic versus refractive (anisometropic/bilateral).

RESULTS

The sample had a total of 1665 participants, 1369 (82.2%) without amblyopia and 296 (17.8%) with amblyopia. Among amblyopia: 67.9% (n = 201) refractive, 32.1% (n = 95) strabismic. Within refractive amblyopia: 63.7% (n = 128) anisometropic and 36.3% (n = 73) bilateral. The mean age at first consultation was 6.24 ± 3.90 years-old: 6.39 ± 3.98 for non-amblyopic and 5.76 ± 3.58 for amblyopic. Among amblyopia subgroups, there were significant differences in mean age at first consultation (F3,1250 = 8.45; p < 0.001; η2 = 0.020). Strabismic and bilateral refractive amblyopia were referred earlier, when compared to non-amblyopia or anisometropic amblyopia (p < 0.05). Anisometropic amblyopia had the highest first consultation mean age: 6.92 ± 3.57 years-old.

DISCUSSION

Without specific pre-school screening, children with amblyopia were referred to their first ophthalmologic evaluation significantly later than desired, especially anisometropic amblyopia, with a postschool mean age for first consultation.

CONCLUSION

Recognizing high-risk children is essential for earlier referral and helps minimize future visual handicap.

Prevalence and association of refractive anisometropia with near work habits among young schoolchildren: The evidence from a population-based study

Background

Lifestyle behaviour may play a role in refractive error among children, but the association between near work habits and refractive anisometropia remains unclear.

Methods

We estimated the prevalence of refractive anisometropia and examined its association with near work activities among 23,114 children in the Myopia Investigation Study in Taipei who were grade 2 elementary school students at baseline in 2013 and 2014. Baseline data on demographics, medical history, parental history and near work habits were collected by parent-administered questionnaire survey. Refractive status was determined by cycloplegic autorefraction. Refractive anisometropia was defined as the spherical equivalent difference ≥ 1.0 diopter between eyes.

Results

The prevalence of refractive anisometropia was 5.3% (95% confidence interval [CI], 5.0% to 5.6%). The prevalence and severity of refractive anisometropia increased with both myopic and hyperopic refractive error. Multivariate logistic regression analysis revealed that refractive anisometropia was significantly associated with myopia (odds ratio [OR], 2.98; 95% CI, 2.53–3.51), hyperopia (OR, 2.37; 95% CI, 1.98–2.83), degree of astigmatism (OR, 1.005; 95% CI, 1.005–1.006), amblyopia (OR, 2.54; 95% CI, 2.06–3.12), male gender (OR, 0.88; 95% CI, 0.78–0.99) and senior high school level of maternal education (OR, 0.69; 95% CI, 0.52–0.92). Though anisometropic children were more likely to spend more time on near work (crude OR, 1.15; 95% CI, 1.02–1.29) and to have less eye-to-object distance in doing near work (crude OR, 1.15; 95% CI, 1.01–1.30), these associations became insignificant after additional adjustment for ocular, demographic and parental factors.

Conclusions

The present study provides large-scale, population-based evidence showing no independent association between refractive anisometropia and near work habits, though myopia is associated with refractive anisometropia.

[Investigations on the prevalence of axial and refractive anisometropia]

PURPOSE

The aim of this paper was to describe the prevalence of axial and refractive anisometropia among students 18 years old.

MATERIAL AND METHODS

The study was carried out among high school students 18 years old in Szczecin, Poland. A total of 1040 students including 381 boys and 659 girls were examined. Every student underwent retinoscopy after cycloplegia using 1% Tropicamide. The differences in spherical equivalents in the right and left eye, were calculated. Students who had anisometropia >1.00 Dsph, were qualified to the next part of the studies, in which examinations using an autorefractometer, keratometer, biometric ultrasounds as well as the IOL Master were carried out. In the group of 70 students (which makes up 7% of the examined population), qualified to the next part of the examinations, a total of 20 participants (2%) declined. The remaining 50 students (5%) were divided into two groups. One group consisted of students with axial anisometropia, while the other consisted of students with refractive anisometropia. All of the collected data were stored in an electronic database using the Microsoft EXCEL computer program and analyzed with Statistica 6.1 software. In the analysis of nominal variables the Fisher exact test was used. P values of less than 0.05 were considered statistically significant.

RESULTS

In the conducted studies a higher prevalence of axial anisometropia (60%) compared to refractive anisometropia (40%) was observed, but the difference did not reach statistical significance (p = 0.20). No association between the type of anisometropia and gender was found in the studies. Axial anisometropia was found in 60% of boys and girls in the study group qualified to the second part of the examinations, while refractive anisometropia was found in 40% of boys and girls qualified to the next part of the examinations.

CONCLUSIONS

Anisometropia in students 18 years old is caused more often by different axial length rather than by different refraction of the eye.

Longitudinal follow-up of hypermetropic children identified during preschool vision screening

PURPOSE

Early childhood hypermetropia is an important risk factor for the development of amblyopia and esotropia. Understanding the natural history of these complications aids in management decisions.

METHODS

A retrospective observational review was undertaken of 149 patients referred from a preschool photoscreening program who were determined to have hypermetropia of >or=+3.75 D spherical equivalent on criterion standard examination and were treated/followed by one group of academic pediatric ophthalmologists. The prevalence and incidence of accommodative esotropia and amblyopia were determined.

RESULTS

At presentation 19% of hypermetropic children had amblyopia, 32% had esotropia, and 13% had both. Follow-up data of 108 patients during a mean of 40 months showed that 20 (24%) of 83 initially nonamblyopic patients developed amblyopia and that 22 (33%) of 67 initially nonstrabismic patients developed accommodative esotropia. Of patients initially managed with observation, 38% (6 of 16) developed amblyopia, and 31% (5 of 16) developed accommodative esotropia as compared with 21% (14 of 67) and 33% (17 of 51), respectively, for those given full or partial refractive correction. For patients without amblyopia or strabismus at presentation, only 20% developed amblyopia and 35% esotropia. Strabismic patients responded well to treatment, with no cases developing partially accommodative strabismus requiring surgery during follow-up.

CONCLUSIONS

In this case series we found a high prevalence of amblyopia and strabismus. The results support the importance of early preschool vision screening and spectacle correction of moderate to high hypermetropia (>+3.50 D) to reduce the risk of amblyopia, although more research is needed.

Prevalence of habitual refractive errors and anisometropia among Dutch schoolchildren and hospital employees

PURPOSE

Refractive error (RE) is suggested to cause not only visual impairment, but also functional problems such as aspecific health complaints and lower levels of school achievement. During the last few decades the prevalence of myopia has increased worldwide, especially in Asia. We investigated the prevalence of habitual RE and anisometropia in a Dutch population of children and employees.

METHODS

In a cross-sectional study, RE in both eyes of 520 children (aged 11-13 years) and 444 hospital employees (aged 17-60 years) were measured using an autorefractometer. The measurements were performed without using a cycloplegium. Pearson's correlation coefficient (r) was used to analyse correlations between the right and left eyes. Chi-square tests were used to test the differences between subgroups according to gender and age.

RESULTS

In schoolchildren 28% of right eyes were myopic (> 0.50 D) and 8% hyperopic (> 0.50 D). Pearson's r between right and left eyes for spherical equivalent power (SEP) was 0.93. The mean cylinder deviation in right eyes was 0.26 D (range 0.00-4.50 D). Anisometropia > 1.00 D was present in 4.6% of children; 22% of children were not optimally (> 0.50 D) corrected. In hospital employees, 30% of right eyes were myopic (> 0.50 D) and 10% hyperopic (> 0.50 D). Pearson's r between right and left eyes for SEP was 0.53. The mean cylinder deviation in right eyes was 0.35 D (range 0.00-5.75 D). Anisometropia > 1.00 D was present in 25% of employees. Anisometropia was more frequently present in employees aged 40-60 years, than in those aged 17-39 years (30% versus 18%; p = 0.02, Cramer's V = 0.15).

CONCLUSIONS

Refractive errors are common in children aged 11-13 years and in working adults aged 17-60 years. Distributions of sphere and cylinder deviations are similar for Dutch schoolchildren and hospital employees. Surprisingly, anisometropia proved to be more prevalent with age. In children many eyes are not optimally corrected. Increased attention should be paid to uncorrected and miscorrected REs.

Field testing of the plusoptiX S04 photoscreener

PURPOSE

To evaluate the diagnostic accuracy of the plusoptiX S04 digital photoscreener in a school screening program.

METHODS

Between 2006 and 2007, 1343 information pamphlets/consent forms were sent to all junior kindergarten students in a local school district. Assistants from a local public health unit photographed 307 children. Of these, 271 children received an independent ophthalmic examination by a physician. Photographic results were compared with the those of the ophthalmic examination. Amblyopia risk factors were defined as anisometropia >1 D (sphere or cylinder), astigmatism >1.25 D, myopia >3 D, hyperopia >3.5 D, any manifest strabismus, and any media opacity.

RESULTS

Photographic and examination results agreed in 94% of cases. Sensitivity in detecting amblyopia risk factors was 83%; specificity was 95%. The positive and negative predictive values were 73% and 97%, respectively. The untestable/unusable rate was 1%.

CONCLUSIONS

These results compare favorably with a previously reported (but no longer available) digital photoscreening camera and are superior to results obtained with other off-axis photoscreening devices that require human interpretation. On the basis of these results, in a real-world screening program, the camera would falsely refer 4% of those screened and would fail to correctly refer 2%. The accuracy of the plusoptiX S04 camera in detecting amblyopia risk factors appears sufficiently high to consider its further deployment in a widespread school screening program.

Ocular Dominance, Laterality, and Refraction in Singaporean Children

PURPOSE

To explore the effect of dominance and laterality on refractive error and axial length.

METHODS

Ocular dominance was assessed with the hole-in-the-card test in 543 children during their 2006 follow-up visits for the Singapore Cohort study Of the Risk factors for Myopia (SCORM). Data were compared to cycloplegic refractions and axial lengths measured by ultrasound.

RESULTS

The spherical equivalent refraction was essentially the same between the right and left eyes, although there was a small but statistically significant longer axial length in the right eyes. Right and left ocular dominance was noted in 58% and 30% of the subjects, respectively, with 12% having no eye preference. There was no significant difference in spherical equivalent refraction (2.56 +/- 2.46 D [mean +/- SD] vs. -2.45 +/- 2.52 D, P = 0.22) or axial length (24.36 +/- 1.19 mm vs. 24.32 +/- 1.18 mm, P = 0.05) between dominant and nondominant eyes. In subjects with anisometropia >or=0.5 D, dominant eyes were more myopic in 52%. Dominant eyes, however, had less astigmatic power (-0.88 +/- 0.80 D versus -1.00 +/- 0.92 D; P < 0.001).

CONCLUSIONS

Ocular laterality and dominance have no significant effect on spherical equivalent. All axial length and astigmatic differences were small and clinically insignificant. The study findings suggest that in Singaporean children, bias is not present in those investigations that restrict analyses to right or left eyes. Although there is no apparent association between refraction and ocular dominance in young Singaporean children, more research is needed to resolve the disparate results in existing reports.

Impact of amblyopia on vision at age 12 years: findings from a population-based study

AIMS

To report prevalence of amblyopia and long-term impact of its treatment on vision in a population-based sample of 12-year-old Australian children.

METHODS

Logarithm of minimum angle of resolution (logMAR) visual acuity (VA) was measured in 2353 children (response rate 75.3%); visual impairment was defined as VA<6/12. Amblyopia was defined using various criteria of best-corrected VA, together with an amblyogenic factor and absence of significant organic pathology. Corroborative historical data on previous diagnosis and treatment were obtained from parental questionnaires.

RESULTS

Forty-four children (1.9%) were diagnosed with amblyopia, unilateral in 40 and bilateral in four. Isolated anisometropia was the most frequent cause (41%), followed by strabismus (25%), combined anisometropia and strabismus (23%), and high ametropia (9%). Myopia, hyperopia, and astigmatism were present in 28, 51, and 44% of amblyopic children, respectively, compared to 12, 4, and 9% of non-amblyopic children. Mean best-corrected VA in amblyopic eyes was 44.5 logMAR letters (Snellen equivalent 6/9), range: 11-60 letters. Most children with amblyopia (84%) had been treated. Only 27% were visually impaired in their amblyopic eye.

CONCLUSIONS

This report documents a low amblyopia prevalence in a population of 12-year-old Australian children. Amblyopic visual impairment was infrequent in this sample despite absence of mandatory vision screening.

Validated portable pediatric vision screening in the Alaska Bush. A VIPS-like study in the Koyukon

BACKGROUND

Photoscreening and remote autorefraction showed promise in the urban "Vision in PreSchoolers Study." We transported a comparative screening with confirmation program to a remote part of interior Alaska.

METHODS

Eighty children from villages in the Koyukon region received onsite three-pronged vision screening followed by gold-standard confirmatory exams. Each had patched HOTV acuity, photoscreening and Suresight remote autorefraction.

RESULTS

There was a high prevalence of amblyopia and vision disorders in these villages. Acuity testing was moderately valid but not useful for children under four years old. Suresight has specificity over 90 percent with sensitivity of 60 percent. Photoscreening had specificity over 95 percent and sensitivity of 70 percent and was better than Suresight for children under age four.

CONCLUSION

The Welch Allyn Suresight had similar high validity in the Koyukon as in Vision in Preschoolers (VIPS) and provides immediate, onsite results. Photoscreening, particularly with commercial digital flash cameras and specific interpretation, is a cost effective screening tool particularly for younger children.

Development of astigmatism and anisometropia in preterm children during the first 10 years of life: a population-based study

OBJECTIVE

To assess the development of astigmatism and anisometropia to 10 years of age in preterm children, previously included in a population-based study on the incidence of retinopathy of prematurity.

METHODS

Cycloplegic retinoscopies were performed in 198 preterm children at 6 months, 2(1/2) years, and 10 years of age. We analyzed the development of astigmatism of 1 diopter (D) or more and anisometropia of 1 D or more.

RESULTS

The amount and prevalence of astigmatism declined between 6 months and 2(1/2) years of age and then remained stable. We found no difference in the course of astigmatism at different ages with regard to stage of retinopathy of prematurity. The amount of anisometropia increased, but its prevalence remained unchanged. Multiple regression analyses showed that astigmatism of 1 D or more at 2(1/2) years of age and cryotreated severe retinopathy of prematurity were risk factors for astigmatism at 10 years of age, and that anisometropia of 2 D or more at 2(1/2) years of age was a risk factor for anisometropia at 10 years of age.

CONCLUSIONS

The development of astigmatism and anisometropia showed a similar course, regardless of stage of retinopathy of prematurity. The retinoscopy findings at 6 months of age were of no value in predicting astigmatism and anisometropia at 10 years of age, but the refraction at 2(1/2) years of age was. Retinoscopy at about 2(1/2) years of age in all preterm children may be useful for detecting astigmatism and anisometropia that will persist in children of school age.

Anisometropia in a tropical hospital

BACKGROUND

This was to determine the prevalence and distribution of anisometropia and to study the difference in refraction between the eyes of patients with anisometropia and look for evidence of laterality, if any.

STUDY DESIGN

A prospective study of 1819 consecutive new patients seen in our clinic with no other pathology except refractive error between November 1998 and December 2002 were included in the study. Information obtained included age, sex, visual acuity, type and degree of anisometropic error. Non-parametric statistical methods were used for analysis.

RESULTS

Of 1819 patients seen, 815 (44.81%) had anisometropia. There were 389 males and 426 females with a male to female ratio of 1.00 to 1.1 and a mean age of 35.15 (standard deviation 17.38). Of the 815 patients, 476 (58.40%) had spherical anisometropia and 339 (41.60%) had cylindrical anisometropia. Myopic anisometropia (253 (31.04%) was the most common. Of the spherical anisometropic errors excluding the mixed types, majority (245 (57.65%) had a difference of 0.25 dioptres and 28 (6.59%) had a difference of 2.00 dioptres and above. The highest difference of 8 dioptres was found in only one patient. The mean error degrees were higher on the left in both myopia and hypermetropia.

CONCLUSION

Anisometropia is quite common in this environment. There is a tendency for the left to be higher contrary to previous findings. In order to allow for data comparison between countries and give room for the occasional high difference between eyes, it may be better to use both eyes in data analysis contrary to previous impression.

Longitudinal study of anisometropia in Singaporean school children

PURPOSE

The purpose of this study was to document the incidence rates of anisometropia, year-by-year prevalences, changes in the intereye difference in spherical equivalent (SE), and its association with myopia progression and axial length changes in a cohort of Singaporean school children.

METHODS

This is a prospective cohort study of Singaporean school children (n = 1979) aged 7 to 9 years who were examined annually with cycloplegic refraction and ultrasonography over a 3-year period.

RESULTS

In the 1908 children without anisometropia at commencement, the 3-year cumulative incidence rate of anisometropia (difference in SE at least 1.0 D) was 144 (7.55%; 95% CI: 6.42-8.85). The mean intereye difference in SE in all children at baseline was 0.29 +/- 0.46 D (SD: 0.46) and increased to 0.44 D (0.59) on the last examination. On the initial examination, 3.6% (95% CI: 2.8-4.4) or 71 children had anisometropia. Of the 59 of 71 children who completed all examinations, only 3 (5.1%) had an increase in the intereye difference in SE by at least 0.5 D, whereas 2 (3.4%) had a decrease of at least 0.5D. The mean intereye difference in SE was stable between visits. The change in intereye difference in SE correlated with the change in intereye axial length (r = 0.43). Compared with the isometropic children, each eye of the anisometropic children had a higher rate of progression of myopia.

CONCLUSIONS

The 3-year incidence of anisometropia was 7.55% in these young Singaporean children. Although the frequency of anisometropia increased with time, the difference in SE between eyes tended to remain stable.

Prevalence and associations of anisometropia and aniso-astigmatism in a population based sample of 6 year old children

AIM

To study the distribution of anisometropia and aniso-astigmatism in young Australian children, together with clinical and ocular biometry relations.

METHOD

The Sydney Myopia Study examined 1765 predominantly 6 year old children from 34 randomly selected Sydney schools during 2003-4. Keratometry, cycloplegic autorefraction, and questionnaire data were collected.

RESULTS

Spherical equivalent (SE) anisometropia (> or =1 dioptre) prevalence was 1.6% (95% confidence interval (CI) 1.1% to 2.4%). Aniso-astigmatism (>or =1D) prevalence was 1.0% (CI: 0.6% to 1.6%). Both conditions were significantly more prevalent among moderately hyperopic (SE > or =2.0D) than mildly hyperopic (SE 0.5-1.9D) children. Myopic children (SE < or =-0.5D) had higher anisometropia prevalence. Neither condition varied by age, sex, or ethnicity. In multivariate analyses, anisometropia was significantly associated with amblyopia, odds ratio (OR) 29, (CI: 8.7 to 99), exotropia (OR 7.7, CI: 1.2 to 50), and neonatal intensive care unit (NICU) admission (OR 3.6, CI: 1.1 to 12.6). Aniso-astigmatism was significantly associated with amblyopia (OR 8.2, CI: 1.4 to 47), maternal age >35 years (OR 4.0, CI: 1.3 to 11.9), and NICU admission (OR 4.6, CI: 1.2 to 17.2). Anisometropia resulted from relatively large interocular differences in axial length (p<0.0001) and anterior chamber depth (p = 0.0009). Aniso-astigmatism resulted from differences in corneal astigmatism (p<0.0001).

CONCLUSION

In this predominantly 6 year old population, anisometropia and aniso-astigmatism were uncommon, had important birth and biometry associations, and were strongly related to amblyopia and strabismus.

Anisometropia is independently associated with both spherical and cylindrical ametropia

PURPOSE

To explore the associations between anisometropia and spherical ametropia, astigmatism, age, and sex.

METHOD

Associations between the prevalence and magnitude of anisometropia with age, sex, spherical power, and cylindrical power, were assessed in a group of 90,884 subjects attending optometry practices in the United Kingdom. Logistic regression models were used to assess the independent contribution of each explanatory variable.

RESULTS

Logistic regression analyses that included all subjects or just those aged 20 to 40 years showed that spherical ametropia and astigmatism were independently associated with anisometropia (myopes, P < 1.0E-61; hyperopes, P < 1.0E-11). Anisometropia was relatively stable between the ages of 20 and 40 years, but then became more common with age, in myopes from the age of 40 years onward (P < 0.003) and in hyperopes from the age of 70 years onward (P < 1.0E-6). Sex was not associated with anisometropia to a clinically significant extent.

CONCLUSIONS

This is the first study to show an independent association between anisometropia and both spherical ametropia and astigmatism. The results also suggest that the previously noted increased prevalence of anisometropia with age occurs later in hyperopes than in myopes, once other covariates have been controlled for. However, it could not be ruled out that this latter effect was due to clinical selection bias in our sample. The findings suggest that research projects involving the recruitment of highly ametropic subjects, such as those investigating the genetics of refractive error, may benefit by avoiding the use of stringent inclusion criteria for anisometropia, because otherwise a large proportion of the relevant population will be excluded.

Refractive error and ocular biometry in Jordanian adults

The aim of this study was to establish the prevalence of refractive errors in Jordanian adults of working age, and to study the ocular biometric correlates of refractive error in this population. Refractive error and ocular biometry were measured in 1093 Jordanian adult subjects aged 17-40 years to determine the prevalence of refractive error, and explore structural correlations of ametropia. Refractive error was measured using a Grand-Seiko GR-3100K closed-view infrared autorefractor. Ocular component measurements were made using A-scan ultrasonography and autokeratometry. The prevalence of myopia [spherical equivalent refraction (SER) less than -0.50 DS] and hyperopia (SER greater than +0.50 DS) was 53.71 and 5.67% respectively; 40.62% of the sample was emmetropic (refraction between +0.50 D and -0.50 D inclusive in both principal meridians). The distribution of SER was found to show marked leptokurtosis, exhibiting a peak between plano and 1 D of myopia. Corneal radius, anterior chamber depth, crystalline lens thickness, vitreous chamber depth and axial length (AL) parameters were normally distributed in the population studied. AL to corneal curvature ratio was not normally distributed, and showed marked leptokurtosis. Linear regression analysis showed that AL correlated most closely with spherical equivalent refractive error. This study has established a database of refractive error prevalence and ocular biometric correlates of ametropia in a Middle Eastern population of working age.

Refractive status of indigenous people in the northwestern Amazon region of Brazil

PURPOSE

The purpose of this study was to investigate the refractive status of the illiterate indigenous people of the upper Rio Negro region of the Amazon rain forest in northwestern Brazil.

METHODS

From an overall sample of 486 people, 259 indigenous people and 78 Brazilians between 12 and 59 years of age with no compromising optical opacities were refracted with cycloplegic retinoscopy. Subjects were categorized as indigenous if they had at least three generations of indigenous ancestry with no folklore suggesting other ancestors.

RESULTS

Myopia was rare among the indigenous population. Only 2.7% of eyes showed myopia of -1.00 D or more and 1.6% (four people) had bilateral myopia of -1.00 D or more. Half of this small group were the only educated indigenous people examined. The prevalence of astigmatism and anisometropia equal to or >1.00 D was 15.5% and 8.2%, respectively. Most of the astigmatism in the indigenous people had an against-the-rule axis. Age was not associated with the refractive errors of the indigenous people. Brazilians from the small city in which the study was performed had higher rates of myopia (6.4% of eyes and 5.1% of subjects bilaterally). Older preeducation adults also had a very low prevalence of myopia (3.2% of eyes and 2.0% of subjects), whereas the younger, slightly educated Brazilians had a higher prevalence of myopia (11.3% of eyes and 9.7% of subjects).

CONCLUSION

The low prevalence of myopia in the illiterate indigenous people is consistent with other studies and suggests that myopia is related to literacy. The generational change among the local mixed race Brazilians further supports this conclusion. The relatively high rates of astigmatism and anisometropia in the indigenous people were unusual for a predominantly emmetropic sample.

Prevalence of anisometropia in Taiwanese schoolchildren

BACKGROUND AND PURPOSE

This study investigated the prevalence and distribution of anisometropia in Taiwanese schoolchildren using nationwide data from refractive surveys performed in 1995 and 2000.

METHODS

Complete survey data was obtained for 11,175 students in 1995 and 10,878 students in 2000. The refractive status of each student was measured using an autorefractometer under cycloplegia and rechecked with retinoscopy. The difference in refractive status between each participant's eyes was determined. Chi-squared statistic was used to assess the difference between the 2 surveys. Multiple linear regression was used to determine the trend and effects of covariates.

RESULTS

Most of the schoolchildren (77.6% in 1995, 71.9% in 2000) were not anisometropic. Most of the anisometropic differences were in the range 0.5 to 1.0 D (14.1% in 1995 vs 17.9% in 2000). About 6% of schoolchildren in 1995 and 7.0% in 2000 had anisometropic differences in the range from -1.0 to -2.0 D. Fewer than 4% of students had a level of anisometropia greater than 2.0 D (2.7% vs 3.2%, respectively). The prevalence of anisometropia and the extent of anisometropic difference both increased with age and with maximal myopic refraction (both p < 0.0001). Both the prevalence and extent of anisometropia showed significant differences between the 2 surveys (both p < 0.0001).

CONCLUSIONS

Most of the Taiwanese schoolchildren surveyed were non-anisometropic. The prevalence and amount of anisometropia were significantly increased from 1995 to 2000. The mechanisms responsible for these increases have not been determined, but may be related to increase of myopic refraction.

Epidemiologic study of anisometropia in students of Natal, Brazil

PURPOSE

To perform an epidemiologic study in students in Natal/Brazil, with relation to refractional anisometropia, evaluating criteria such as: gender, age, and association with strabismus and amblyopia.

METHODS

A study of 1,024 students randomly selected from several districts of Natal/Brazil was undertaken by the Department of Ophthalmology of the Federal University of Rio Grande do Norte (UFRN), observing the following criteria of > or =2 spherical or cylindrical diopter refractional anisometropia relating it to sex, age, association with strabismus, amblyopia and anisometropia classification.

RESULTS

We found a prevalence of 2% (N=21) anisometropia in the students. The female gender predominated with 81% (N=17). In students with anisometropia, we observed an association with strabismus in 9.5% of cases (N=2), both with exotropia. The association of anisometropia with amblyopia occurred in 47.6% of the cases (N=10), with 8 cases of unilateral amblyopia and 2 cases of bilateral amblyopia.

CONCLUSIONS

There was a predominance of anisometropia in females, and an increased prevalence of strabismus and amblyopia in students with anisometropia.

An analysis of high myopia in a pediatric population less than 10 years of age

PURPOSE

The purpose of this article is to document a comprehensive clinical profile-including the prevalence of amblyopia, strabismus, and anisometropia-of a pediatric population less than 10 years of age who manifested 6.00 diopters or more of myopia.

METHOD

A retrospective record review was performed on all pediatric patients less than 10 years of age, examined at the State University of New York (SUNY) State College of Optometry between 1998 and 2001, and with a spherical equivalent of 6.00 diopters or more of myopia.

RESULTS

One hundred seventy-eight patients met the criteria. Amblyopia or reduced corrected visual acuity was present in 75.8% of the patients. Strabismus was present in 31.5% of the patients, with essentially equal numbers of esotropes and exotropes. Anisometropia was present in 35.4% of the patients. One hundred forty-five patients had high myopia in the absence of significant ocular or systemic compromising conditions. In this sample of 145, strabismus or anisometropia was an etiology for amblyopia. There was a greater prevalence of bilateral high myopia (64.8%) than unilateral high myopia. Anisometropia was present in 10.6% of the bilateral high myopes, and 78.4% of the unilateral high myopes.

CONCLUSION

Children less than 10 years of age with high myopia have a high risk of having amblyopia, strabismus, and anisometropia.

[Occurrence of anisometropia among students ranging from 6 to 18 years of age]

PURPOSE

To determine the prevalence of anisometropia among students ranging from 6 to 18 years of age.

MATERIAL AND METHODS

5023 students from elementary schools, junior high schools and high schools, aged 6-18 years were examined. Measurements of visual acuity as well as retinoscopy after cycloplegia have been carried out. The data were analyzed using chi-square test and the coefficients of rang Spearman's correlation were calculated.

RESULTS

It was found that 6% of the students suffer from anisometropia. No influence of the students' age on the prevalence of anisometropia was observed. It was found that anisometropia occurs more frequently among boys than among girls.

Occurrence of refractive errors among students who before the age of two grew up under the influence of light emitted by incandescent or fluorescent lamps

PURPOSE

The aim of the study was to determine whether the development of refractive errors could be associated with exposure to light emitted by incandescent or fluorescent lamps.

MATERIAL AND METHODS

3636 students were examined (1638 boys and 1998 girls, aged 6-18 years, mean age 12.1, SD 3.4). The examination included skiascopy with cycloplegia. Myopia was defined as refractive error < or = -0.5 D, hyperopia as refractive error > or = +1.5 D, astigmatism as refractive error > 0.5 DC. Anisometropia was diagnosed when the difference in the refraction of both eyes was > 1.0 D. The parents of all the students examined completed a questionnaire on the child's light exposure before the age oftwo. Data were analyzed statistically with the chi2 test. P values of less than 0.05 were considered statistically significant.

RESULTS

It was observed that sleeping until the age of two in a room with a light turned on is associated with an increase in the occurrence of anisometropia (p < 0.02) as well as with a reduction in the prevalence of emmetropia (p < 0.05). It was also found that light emitted by fluorescent lamps leads to more frequent occurrence of astigmatism (p < 0.01).

Anisometropia in Singapore school children

PURPOSE

To report the prevalence rates of anisometropia in a school population and determine the relative contribution of refractive power and axial length to the measured anisometropia.

DESIGN

Population-based cross-sectional study.

METHODS

Autorefraction, keratometry, and ultrasonography studies were made.

SETTING

Three schools, located on the eastern, northern, and western part of Singapore.

STUDY POPULATION

In all, 1,979 children aged 7 to 9 years were recruited for this study. The study sample included Chinese (n = 1,481), Malay (n = 324), and Asian Indian (n = 174) children; 720 subjects have myopia (spherical equivalent <= -0.5 diopters) in at least one eye.

MAIN OUTCOME MEASURE

Anisometropia.

RESULTS

The prevalence rates of anisometropia, in terms of spherical equivalent (SE) difference of at least 1.5 diopters and 2.0 diopters were 1.57% (95% confidence interval [CI]: 1.1, 2.2) and 1.01% (95% CI: 0.6, 1.6), respectively. The prevalence rate of anisometropia (at least 2.0 diopters) among the children with at least one myopic eye was 2.4% (95% CI: 1.4, 3.8), whereas in those without any myopic eyes, the prevalence rate was only 0.2% (95% CI: 0.06, 0.8). The spherical equivalent difference between the right and left eyes was positively correlated with the difference in axial lengths (P <.001). The difference in corneal refractive power is not statistically different between the anisometropic and the nonanisometropic children.

CONCLUSIONS

The anisometropia prevalence rate in a childhood population with a relatively high prevalence of myopia was reported. The origin of the anisometropia is axial, and these results suggest that the differential rate of elongation between the two eyes of nonmyopic subjects results in anisometropia.

Prevalence of refractive errors in teenage high school students in Singapore

We aimed to study the prevalence of refractive conditions in Singapore teenagers. Grade 9 and 10 students (n = 946) aged 15-19 years from two secondary schools in Singapore were recruited. The refractive errors of the students' eyes were measured using non-cycloplegic autorefraction. Sociodemographic data and information on risk factors for myopia (such as reading and writing) were also obtained using an interviewer-administered questionnaire. The prevalence of refractive conditions was found to be: myopia [spherical equivalent (SE) at least -0.50 D] - 73.9%, hyperopia (SE at least +0.50 D) - 1.5%, astigmatism (cylinder at least -0.50 D) - 58.7% and anisometropia (SE difference at least 1.00 D) - 11.2%. After adjusting for age and gender, currently doing more than 20.5 h of reading and writing a week was found to be positively associated with myopia [odds ratio 1.12 (95% CI 1.04-1.20, p = 0.003)], as was reading and writing at a close distance and a better educational stream. The prevalence of myopia (73.9%) in Singapore teenagers is high. Current reading and writing habits, reading at close distances and a better educational stream are possible risk factors for myopia.

Asymmetric refraction in an older population: the Blue Mountains Eye Study

PURPOSE

To describe prevalence and associations of asymmetric refraction in an older population.

METHODS

All participants in the Blue Mountains Eye Study had comprehensive eye examinations, including refraction. Spherical equivalent (SEq = sum sphere +.5 cylinder), in diopters, defined refractive error. Refractive asymmetry was assessed in phakic participants; anisometropia was defined as > or =1.0 diopters SEq difference between eyes.

RESULTS

Anisometropia was present in 14.7% of participants. Mean refractive asymmetry (in diopters) in persons aged <60 years was 0.43; 60 to 69 years, 0.51; 70 to 79 years, 0.72; and 80+ years, 0.88. Prevalence and severity of anisometropia increased with age (P <.001), increasing ametropia or astigmatism. Associations included older age, cataract, and increasing ametropia. Myopic participants >-3.0 diopters had the highest anisometropia prevalence.

CONCLUSIONS

Refractive asymmetry was associated with age, increasing ametropia, and cataract.

[Epidemiology of refraction disorders]

THE PURPOSE OF THIS STUDY

Is to appreciate the prevalence and incidence of the refraction disturb among the children aged 7-11 years old.

MATERIAL AND METHOD

Using the descriptive study method, we examined 3562 children aged between 7 to 11 years old, a representative group for Bihor Country.

RESULTS

Among the studied children batch, hypermetropy represents 89.8%, myopia 1.4%, astigmatism 4.9% and anisotropy 4%. The amblyopy was diagnosed in 474 cases (13.3%). The medium amblyopy is predominant.

CONCLUSIONS

The refraction disturb incidence is 9.5@1000 and their prevalence is 82.4@1000. In the studied group, the hypermetropy is predominant. In the group of children with 10 years old, we encountered the greatest number of myopia and emetropy. Amblyopic represents 13.3% from all cases. It is required an ophthalmological health program that will include the refraction disturb with children, as well.

Distribution of refractive error in healthy infants

PURPOSE

Few data exist regarding the upper limits of refractive error distributions in healthy infants; the data that do exist are biased because they were selected from the records of pediatric ophthalmology practices. We sought to obtain these data to validate examination failure criteria for vision screening.

METHODS

We reviewed records from all children age birth to 5 years seen at the Tennessee Lions Eye Center at Vanderbilt Children's Hospital with a billing diagnosis of nasolacrimal duct obstruction and no comorbid ocular diagnoses except for refractive error. This was to avoid referral bias for any condition that could have influenced refractive error. All patients received a complete eye examination and cycloplegic refraction. Cumulative probability distribution (CPD) plots and means for spherical and cylindrical refractive error and anisometropia were prepared.

RESULTS

One hundred thirty patients were studied; mean age was 15.5 +/- 9.9 months (range, 2 days to 66 months). The mean refractive error (spherical equivalent) was +1.4 D +/- 1.1 D. CPD plot analysis showed 95% of hyperopia to be < +3.25 D. Two children had myopia </=-1.00 D. The mean astigmatism was +0.2 D +/- 0.4 D, and 74% of patients had no astigmatism. Seven children had astigmatism > +1.00 D in one eye. CPD plot analysis showed 95% of astigmatism to be < +1.50 D and 95% of meridional anisometropia to be < 1.50 D. Six children had anisometropia >/=1.50 D, and 3 children had anisometropia > 3.00 D.

CONCLUSIONS

At least 95% of children have hyperopia < +3.25 D, astigmatism < +1.50 D, and anisometropia < 1.50 D. This information will prove useful in identifying the natural history and prevalence of amblyogenic factors identified during preschool vision screening.

On the age-related prevalence of anisometropia

Data on the prevalence of non-amblyopic anisometropia amongst adults throughout the world were tabulated and plotted as a function of age. The global picture reveals a systematic rise in the prevalence of anisometropia with age, the fitted linear regression having a significant positive slope of 1% (p < 0.0005) for every 7 years. The distribution may embrace a juvenile rise and a later, post-presbyopic one, perhaps due to neuro-senescence.

Prevalence rates of refractive errors in Sumatra, Indonesia

PURPOSE

To determine the prevalence rates of myopia, hyperopia, astigmatism, and anisometropia in a prevalence survey of adults in Sumatra, Indonesia.

METHODS

A population-based prevalence survey of 1043 adults 21 or more years of age was conducted in five rural villages and one provincial town of the Riau Province, Sumatra, Indonesia. A one-stage household cluster sampling procedure was used wherein 100 households were selected from each village or town. Refractive error measurements were obtained with one of two handheld autorefractors. Household interviews were conducted to obtain information on relevant lifestyle risk factors.

RESULTS

The age-adjusted overall prevalence rates of myopia (SE [spherical equivalent] at least -1.0 D), hyperopia (SE of at least +1.0 D), astigmatism (cylinder of at least -1.0 D), and anisometropia (SE difference of +1.0 D) were 26.1% (95% confidence interval [CI]: 23.4-28.8), 9.2% (95% CI: 7.4-11.0), 18.5% (95% CI: 16.2-20.8), and 15.1% (95% CI: 12.9-17.4), respectively. The age-adjusted overall prevalence rate of high myopia (SE at least -6.0 D) was 0.8% (95% CI: 0.2-1.5). In a multiple logistic regression model, myopia rates varied with age and increased with income. Hyperopia, astigmatism, and anisometropia rates were independently higher in older adults.

CONCLUSIONS

The prevalence rates of myopia in provincial Sumatra are higher than the rates in white populations, but lower than the rates in other urbanized Asian countries such as Singapore. The prevalence rate of high myopia is lower than in most other populations, and other refractive errors are common.

Pediatric Eye Disease Investigator Group. The clinical profile of moderate amblyopia in children younger than 7 years

OBJECTIVE

To describe the demographic and clinical characteristics of a cohort of children with moderate amblyopia participating in the Amblyopia Treatment Study 1, a randomized trial comparing atropine and patching.

METHODS

The children enrolled were younger than 7 years and had strabismic, anisometropic, or combined strabismic and anisometropic amblyopia. Visual acuity, measured with a standardized testing protocol using single-surround HOTV optotypes, was 20/40 to 20/100 in the amblyopic eye, with an intereye acuity difference of 3 or more logMAR lines. There were 419 children enrolled, 409 of whom met these criteria and were included in the analyses.

RESULTS

The mean age of the 409 children was 5.3 years. The cause of the amblyopia was strabismus in 38%, anisometropia in 37%, and both strabismus and anisometropia in 24%. The mean visual acuity of the amblyopic eyes (approximately 20/60) was similar among the strabismic, anisometropic, and combined groups (P =.24), but visual acuity of the sound eyes was worse in the strabismic group compared with the anisometropic group (P<.001). For the patients randomized into the patching group, 43% were initially treated for 6 hours per day, whereas 17% underwent full-time patching. Patients with poorer visual acuity in the amblyopic eye were prescribed more hours of patching than patients with better acuity (P =.003).

CONCLUSIONS

In the Amblyopia Treatment Study 1, there were nearly equal proportions of patients with strabismic and anisometropic amblyopia. A similar level of visual impairment was found irrespective of the cause of amblyopia. There was considerable variation in treatment practices with regard to the number of hours of initial patching prescribed.

[A research of infant refraction in Kunming Municipality]

OBJECTIVE

To study the infant refraction, detect ametropia in mass screening refraction and correct the ametropia properly for the treatment and prevention of amblyopia and strabismus as early as possible.

METHODS

The refraction status of 1 146 children (2 291 eyes, aged 1 month -3 years) were determined with retinoscopy after tropicamide cycloplegia.

RESULTS

The results of statistics showed that 89 eyes (3.88%) had emmetropia, 2 139 eyes (93.37%) hypermetropia, 38 eyes (1.66%) myopia, 560 eyes (24.44%) astigmatism and 25 eyes (1.09%) mixed astigmatism. In cases with ametropia, most of them were mild, and 97 eyes (4.23%) were moderate and severe. Anisometropia occurred in 34 infants (2.97%), and 7 infants (11 eyes, 0.48%) had strabismus. The degree of hypermetropia decreased with the increase of age. The percentage of astigmatism decreased with the age increase (chi(2) = 7.46, P<0.01), and the degree of astigmatism also decreased with the age increase (chi(2) = 26.1l, P < 0.01). Myopia increased with the age increase (chi(2) = 4.06, P < 0.05).

CONCLUSIONS

The prevention of amblyopia and strabismus in children should begin at the infant period, and the cases with moderate and severe ametropia should wear eye glasses as early as possible.

Prevalence of amblyopia and associated refractive errors in an adult population in Victoria, Australia

The study aimed to describe the prevalence of amblyopia and associated refractive errors among an adult Australian population. The Visual Impairment Project (VIP) is a population-based study of age-related eye disease in the state of Victoria, Australia. Data were collected through standardised interviews and orthoptic and ophthalmic dilated examinations. Amblyopia was defined as best-corrected visual acuity of 6/9 or worse in the absence of any pathological cause. The participants were 3,265 urban residents and 1,456 rural residents of the VIP ranging in age from 40-92 years (mean = 59 years; 53% female). The prevalence of unilateral amblyopia was 3.06% (95% C.I. 2.59, 3.53). Amblyopia was not found to be statistically different by age group (p=0.096), gender (p=0.675), or place of birth (p=0.14). Anisometropia was statistically more common (p<0.001) in amblyopic cases (51.1%) compared to the normal population (9.7%), and 54% of amblyopic eyes had visual acuity of worse than 6/12. Amblyopia is a significant cause of unilateral reduced visual acuity in a population aged 40 years and older. Anisometropia was more prevalent and the degree of anisometropia was greater in the amblyopic group compared with the normal population. Oblique astigmatism was more prevalent in the amblyopic group compared with the normal population.

Stimulus deprivation myopia in human congenital ptosis: a preliminary report of 50 unilateral cases

OBJECTIVE

To investigate the frequency of hyperopia and suspected stimulus deprivation myopia in human congenital ptosis.

METHODS

Ametropia was evaluated in both eyes of 50 patients with congenital ptosis. The age at investigation was one year and older, average 6 years and 10 months. The amount of refraction was documented as the spherical equivalent (100% cycloplegia). Differences between the paired eyes of 1.0 dpt or more were defined as anisometropia. Statistical analysis was performed using the chi-square and sign tests.

RESULTS

The frequency of myopia was lower (7/50: 14%) than that of hyperopia (43/50: 86%) in the ptotic eye (p<0.001). However, myopia occurred more often in the ptotic eye (7/50: 14%) than in the fellow eye (3/50: 6%, p>0.3). Myopic anisometropia was found only in the ptotic eye (5/50 vs. 0/50, p = 0.06), but was not more frequent than hyperopic anisometropia: (5/50 vs. 9/50, p>0.4). A covered center of the pupil in 27 out of 50 eyes was not associated significantly with myopia (2 of 27 versus 5 of 23, p>0.2). Altogether, we found a significantly higher rate of myopia <-1 dpt and hyperopia > 2 dpt: 10% vs. 1.4% and 40% vs. 10.2% (p<0.001) in comparison with normal school children.

CONCLUSION

In summary, the following three findings were noted, of which the first two were expected and the third was not. 1. Compared with the normal population, there was an overall higher frequency of myopia in unilateral congenital ptosis. 2. There was a higher frequency of myopia in the ptotic than in the fellow eye. 3. Compared with the normal population, there was also a higher frequency of hyperopia. The clinical presentation of human congenital ptosis may be influenced by compensating head posture, strabismus, accommodation and biochemical effects, and the condition may therefore differ from the classical well-defined animal model of stimulus deprivation myopia.

Refractive errors in Singapore and Xiamen, China--a comparative study in school children aged 6 to 7 years

PURPOSE

To compare and contrast the prevalence of myopia and other refractive errors in Xiamen city, Xiamen countryside (Southern China), and Singapore.

METHODS

One hundred thirty-two schoolchildren aged 6 to 7 years from Xiamen city, 104 from Xiamen countryside, and 146 from Singapore city were recruited to join the study. Cycloplegic autorefraction, keratometry, and biometry measurements were performed on all children.

RESULTS

The prevalence of myopia was 12.3% in Singapore city, 9.1% in Xiamen city, and 3.9% in Xiamen countryside. The prevalence of astigmatism was higher in Singapore compared with Xiamen. The rates of hyperopia and anisometropia were similar in all three locations.

CONCLUSIONS

The myopia rate in Singapore city was higher than in Xiamen city; the lowest rates were found in Xiamen countryside. As the Chinese population from all three sites is of similar genetic stock (predominantly from Southern China), it is postulated that the differences in myopia rates in these three localities may be related to environmental factors.

The development of myopia in Hong Kong children between the ages of 7 and 12 years: a five-year longitudinal study

The purpose of this work was to characterize the development of refractive error in Hong Kong children between the ages of 7 and 12 years. A non self-selected sample of 7-year old children was recruited and followed for 5 years, non-cycloplegic refractions being carried out annually. A life-table was used to determine myopia incidence and prevalence. The mean annual change in the spherical equivalent refraction (SER) was -0.32 D; 75 out of 83 subjects followed for 5 years became less hyperopic or more myopic, the maximum progression occurring between 9 and 11 years of age. The mean change in SER over the 5 years in children who were myopic at age 12 years was significantly greater than that in children who remained non-myopic. The incidence of myopia at age 7-8 years was 9% and at age 11-12 years was 18-20%. At age 7 years the prevalence of progressive myopia was 1.6% and 2.5% of subjects had anisometropia. Any treatment to prevent myopia should start by the age of 6 years and treatment to retard development should commence before age 9 years.

Epidemiologic study of ocular refraction among schoolchildren in Taiwan in 1995

PURPOSE

In order to understand and update the prevalence of myopia in Taiwan, a nationwide survey was performed in 1995.

METHODS

We stratified the cluster sampling by developmental grading of the city, using a size proportional to the population. Two cities were randomly selected from each city grading. The total number of students enrolled was 11,178, including 5,676 boys and 5,502 girls. The refractive status and corneal radius of each student were measured with an autorefractometer under cycloplegia and checked with retinoscopy. Axial length was measured with biometric ultrasound.

RESULTS

The myopic rate was from 12% at the age of 6, it increased to 56% at the age of 12, and then to 76% at the age of 15. A myopic rate of 84% was found for the age range of 16 to 18. The prevalence of high myopia (over -6.0 D) at the age of 18 was 20% in girls and 12% in boys. The mean refractive status became myopic at the age of 9, then increased to -3.92 D in girls and -2.71 D in boys at the age of 18. The increase of axial length is correspondent with the progression of myopia. The anterior chamber depth (ACD) was deeper with age and the severity of myopia, whereas the corneal curvature remained unchanged. The lens thickness became thinner from age 7 to 13, then it became thicker with age and the severity of myopia after age 15. The prevalence and degree of myopia in girls was more severe than in boys.

CONCLUSIONS

The prevalence of myopia in Taiwan increased year by year. The increase in severity and prevalence of high myopia may be due to earlier onset.

Prevalence of amblyopia with anisometropia or strabismus among schoolchildren in the Sultanate of Oman

PURPOSE

The purpose of this study was to investigate the prevalence of common eye disorders in a nationwide school survey conducted in the Sultanate of Oman. The results presented here are those involving amblyopia induced by strabismus or anisometropia.

METHODS

A random selection of primary schools provided a sample that included 49 schools with 6541 children in Grades 1 and 6. Examinations of the eyes of 96%, of these children were conducted doing visual acuity screening to 0.5. All 6292 children had an external eye examination. All children failing the visual acuity test had a complete eye examination.

RESULTS

Amblyopia was found in 0.92%, strabismic amblyopia in 0.48%, anisometropic amblyopia in 0.44% and strabismus with or without amblyopia was seen in 0.9%. There was statistically significantly (p<0.05) more amblyopia in 11-12 year olds (Grade 6) when compared with the 6-7 year olds (Grade 1). This difference was only found among the strabismic children.

CONCLUSION

When compared to Europe or North America the prevalence of strabismic amblyopia is lower, whereas anisometropic amblyopia occurs with approximately the same frequency. The increase of strabismic amblyopia in the older children indicates a development of amblyopia after the age of 6 to 7 years in an untreated population.

Ophthalmological long-term follow up of preterm infants: a population based, prospective study of the refraction and its development

BACKGROUND

Numerous studies have reported an increased risk of refractive errors in prematurely born infants, but only few have been long-term and strictly population based.

METHODS

A 3.5 year ophthalmological long term follow up of 248 preterm infants was performed. The infants had been included in a previous epidemiological study of retinopathy of prematurity (ROP) (birth weight < or = 1500 grams). The incidence of refractive errors and development of refraction were studied, based on retinoscopies at 6 and 30 months of corrected age.

RESULTS

The overall incidence of myopia was 8% at 6 months, of which 35% was transient, and 10% at 30 months. Of the cryotreated infants, 30-40% were myopic at both retinoscopies. The incidence of astigmatism was 52% at 6 months and 26% at 30 months. Astigmatism was associated with ROP, but not with cryotreated ROP itself. Astigmatism "against the rule" was commoner than astigmatism "with the rule". Anisometropia occurred in 6.5% of the infants at 6 months and in 8.4% at 30 months. The incidence of anisometropia was higher in eyes with ROP, particularly in cryotreated eyes, which tended to have high and persistent anisometropia.

CONCLUSION

The risk of refractive errors is higher in preterm infants than in infants born at term, and also prematurely born infants without ROP do run an increased risk of having myopia and anisometropia. We recommend follow up examinations with retinoscopy for all infants included in screening programmes for ROP.

[Correctional aspects of anisometropia in railway machine operators]

The authors assessed occupationally significant visual functions in anisometropy varying in type and degree. Disorders of occupationally significant visual functions depend reliably on anisometropy degree. Correction of anisometropy with recovered vision and binocular functions restores all parameters of night and color vision. Optic and operative correction of anisometropy could be used for rehabilitation of railway machine operators with long length of service. The article provides recommendations to use intraocular lenses for artiphakia in railway machine operators.

Natural history of infantile anisometropia

AIMS/BACKGROUND

In a previous study longitudinal changes of anisometropia were investigated. It was shown that anisometropia arises and vanishes during the emmetropisation process and that the associated risk for amblyopia is low. The aim of this study was to follow acuity and refraction longitudinally in children with marked anisometropia at 1 year of age.

METHODS

Refractive errors and visual acuity were estimated every sixth month for a selected group of 20 children with marked anisometropia > or = 3.0 D (spherical equivalent) at 1 year of age from approximately 3 to 10 years of age.

RESULTS

The children could be classified into three groups. In six subjects the anisometropia increased (mean 1.4 D) and they all developed amblyopia. The remaining children could be classified into two groups of equal size. One group developed no amblyopia and the anisometropia decreased with a mean of 3.0 D. The seven remaining children developed amblyopia and/or strabismus; the mean anisometropia decrease was 1.2 D.

CONCLUSION

Anisometropia at 1 year of age that is larger or equal to 3.0 D will in 90% of the cases still be there at 10 years of age. There is a substantial risk of this group developing amblyopia (60%).

[A survey of the prevalence and causes of eye disorders in primary school children in Antananarivo]

To assess the prevalence and causes of ocular abnormalities in children, we performed a cross-sectional survey with cluster sampling in Madagascar in Antananarivo primary schools in October 1994. Our other aim was to sensitize the sanitary authorities and the students of ophthalmology to the notion of public health ophthalmology in a country where a national blindness prevention program is being established. 1,081 children aged from 8 to 14 years (mean age 10.6 years) were examined. 51, or 4.7%, were diagnosed as having ocular abnormalities. These abnormalities were distributed as follows: 22 cases or 2% of the sample had refractive errors including 0.74% with myopia of less than 6 dioptrics, 0.18% with myopia of more than 6 dioptrics, 0.83% with hypermetropia of less than 6 dioptrics, and 0.28% with hypermetropia of more than 6 dioptrics; 15 cases or 1.4% of the sample had unilateral amblyopia including 0.9% with anisometropia, 0.37% with strabismus, and 0.09% with macular pathology; 8 cases or 0.74% of the sample had strabismus without amblyopia; and 6 cases or 0.57% of the sample had simple medical pathology. The results showed that 29 children were supposed to have an optic correction, including surgical treatment for 12 and medical treatment for 6. The same low frequencies of ocular abnormalities, mainly concerning refractive errors, were found in the literature. However, children suffering from important visual impairment do not attend school, and we cannot generalize the above results for the whole population.

Refractive errors in preterm babies

Fifty preterm neonates were followed up at the age of 6 months and 1 year. In addition to developmental assessment, a complete ophthalmological examination was done on both visits. The largest (62%) gestational age group was of 34-36 weeks. At 6 months, none of the infants had normal vision. At 1 year of age, 64% of the babies had normal vision while incidence of myopia and hypermetropia was 16% and 20%, respectively. There was an inverse relationship noted between gestation and incidence of refractive errors. It was also noted that with decreasing weight, the incidence of myopia increased. Myopia was seen exclusively among infants of birth weight of 2000 g or less. Birth weight had a significant positive correlation with astigmatism. No correlation of asphyxia with refractive errors was observed. It is recommended that all preterm babies should have an ophthalmological examination at one year of age with follow up later on.

A study of amblyopia in 18-19 year old males

During a vision screening of 6,556 National Service pre-enlistees aged 18-19 years at the Medical Classification Centre of Central Manpower Base, 48 subjects were found to have visual acuity of 6/12 or less in one or both eyes in the absence of ocular pathology. The prevalence of amblyopia in this population is 0.73%. Amblyopia was due to anisometropia in 24 cases (50%), strabismus in 9 cases (18.7%), high astigmatism (meridional) in 7 cases (14.5%) and other causes or a combination of factors in 8 cases (16.7%). Strabismic amblyopia is most commonly associated with esotropia. There is a positive association between the severity of amblyopia and the degree of strabismus in strabismic amblyopes. Meridional amblyopia tends to be less severe than most other types of amblyopia. The amblyopes were detected late (average 7-10 years of age) and orthoptic treatment of a small minority of them upon diagnosis was unsuccessful.