Role of near work in myopia: findings in a sample of Australian school children.

PURPOSE: To examine the association of time spent in near work and reading with spherical equivalent refraction (SER) in a population-based sample of 12-year-old Australian schoolchildren. METHODS: Data on the time spent in near-work or outdoor activities per week and estimates for the duration of continuous reading and reading distances, were collected in questionnaires (2353 participants, 75.3% response) in the Sydney Myopia Study between 2004 and 2005; 2339 children underwent a comprehensive eye examination, including cycloplegia. RESULTS: Longer time spent on reading for pleasure and reports of close reading distance (< 30 cm) were associated with a more myopic refraction after adjustment for age, sex, ethnicity, and school type (P(trend) = 0.02 and P = 0.0003, respectively). Time spent in individual near-work activities, however, correlated poorly with SER (all r < or = 0.2) and was not significant in multivariate analyses for myopia (SER < or = -0.50 D), with adjustment for age, sex, ethnicity, parental myopia, school type, and outdoor activity. Children of European Caucasian ethnicity reported spending marginally less time in near work than children of East Asian ethnicity (26.0 h/wk vs. 32.5 h/wk, P < 0.0001). East Asian ethnicity, however, was associated with substantially greater odds of having myopia (odds ratio [OR], 11.0; 95% confidence interval [CI], 7.0-17.4). Near work such as close reading distance (< 30 cm) and continuous reading (> 30 minutes) independently increased the odds of having myopia in this sample of children. CONCLUSIONS: Although myopia was not significantly associated with time spent in near work after adjustment for other factors, there were significant independent associations with close reading distance and continuous reading. These associations may indicate that the intensity rather than the total duration of near work is an important factor.

Myopia and the urban environment: findings in a sample of 12-year-old Australian school children.

PURPOSE: To examine associations between myopia and measures of urbanization in a population-based sample of 12-year-old Australian children. METHODS: Questionnaire data on sociodemographic and environmental factors including ethnicity, parental education, and time spent in near work and outdoor activities were collected from 2367 children (75.0% response) and their parents. Population density data for the Sydney area were used to construct five urban regions. Myopia was defined as spherical equivalent refraction

Outdoor activity reduces the prevalence of myopia in children.

OBJECTIVE: To assess the relationship of near, midworking distance, and outdoor activities with prevalence of myopia in school-aged children. DESIGN: Cross-sectional study of 2 age samples from 51 Sydney schools, selected using a random cluster design. PARTICIPANTS: One thousand seven hundred sixty-five 6-year-olds (year 1) and 2367 12-year-olds (year 7) participated in the Sydney Myopia Study from 2003 to 2005. METHODS: Children had a comprehensive eye examination, including cycloplegic refraction. Parents and children completed detailed questionnaires on activity. MAIN OUTCOME MEASURES: Myopia prevalence and mean spherical equivalent (SE) in relation to patterns of near, midworking distance, and outdoor activities. Myopia was defined as SE refraction < or = -0.5 diopters (D). RESULTS: Higher levels of outdoor activity (sport and leisure activities) were associated with more hyperopic refractions and lower myopia prevalence in the 12-year-old students. Students who combined high levels of near work with low levels of outdoor activity had the least hyperopic mean refraction (+0.27 D; 95% confidence interval [CI], 0.02-0.52), whereas students who combined low levels of near work with high levels of outdoor activity had the most hyperopic mean refraction (+0.56 D; 95% CI, 0.38-0.75). Significant protective associations with increased outdoor activity were seen for the lowest (P = 0.04) and middle (P = 0.02) tertiles of near-work activity. The lowest odds ratios for myopia, after adjusting for confounders, were found in groups reporting the highest levels of outdoor activity. There were no associations between indoor sport and myopia. No consistent associations between refraction and measures of activity were seen in the 6-year-old sample. CONCLUSIONS: Higher levels of total time spent outdoors, rather than sport per se, were associated with less myopia and a more hyperopic mean refraction, after adjusting for near work, parental myopia, and ethnicity.

Prevalence of hyperopia and associations with eye findings in 6- and 12-year-olds.

PURPOSE: To describe the prevalence of hyperopia and associated factors in a representative sample of Australian schoolchildren 6 and 12 years old. DESIGN: Population-based cross-sectional study. PARTICIPANTS: Schoolchildren ages 6 (n = 1765) and 12 (n = 2353) from 55 randomly selected schools across Sydney. METHODS: Detailed eye examinations included cycloplegic autorefraction, ocular biometry, cover testing, and dilated fundus examination. Information on birth and medical history were obtained from a parent questionnaire. MAIN OUTCOME MEASURES: Moderate hyperopia defined as spherical equivalent (SE) refraction of > or =+2.00 diopters (D), and eye conditions including amblyopia, strabismus, astigmatism, and anisometropia. RESULTS: Prevalences of moderate hyperopia among children ages 6 and 12 were 13.2% and 5.0%, respectively; it was more frequent in children of Caucasian ethnicity (15.7% and 6.8%, respectively) than in children of other ethnic groups. Compared with children without significant ametropia (-0.49 < or = SE refraction < or = +1.99 D), the prevalence of eye conditions including amblyopia, strabismus, abnormal convergence, and reduced stereoacuity was significantly greater in children with moderate hyperopia (all Ps < 0.01). Maternal smoking was significantly associated with moderate hyperopia among 6-year-olds (P = 0.03), but this association was borderline among 12-year-olds (P = 0.055). Early gestational age (<37 weeks) and low birth weight (<2500 g) were not statistically significant predictors of moderate hyperopia in childhood. CONCLUSIONS: Moderate hyperopia was strongly associated with many common eye conditions, particularly amblyopia and strabismus, in older children. Birth parameters did not predict moderate hyperopia.

Variation of the contribution from axial length and other oculometric parameters to refraction by age and ethnicity.

PURPOSE: To compare the distribution of spherical equivalent refraction (SER) and other ocular parameters and to assess the contribution from oculometric parameters to SER in two age-specific, cross-sectional samples of children, and in two ethnic groups (European Caucasian and East Asian). METHODS: A random-cluster design was used to recruit predominantly 6-year-old (1765 participants, 78.9% response) and 12-year-old children (2353 participants, 75.3% response) from schools across Sydney, Australia. Data collection included questionnaires and eye examination (keratometry, biometry, and cycloplegic autorefraction). Results of three analytical methods (Pearson correlation, partial correlation coefficient, and linear regression analyses) are reported for 6- and 12-year-old children. RESULTS: Kurtosis for SER and axial length (AL) in the 12-year-old children (14.3 and 2.1, respectively) was similar to that previously reported for the 6-year-old children (11.3 and 0.5). AL showed high correlation (r) with SER in the 6- (r = -0.44) and 12-year-old (r = -0.61) children. Lower correlations for SER with corneal radius (r

Refractive findings in children with astigmatic parents: the Sydney Myopia Study.

PURPOSE: To examine the impact of parental astigmatism on astigmatic error and ocular biometric parameters in children. DESIGN: Population-based cross-sectional study. METHODS: Six-year-old children (n = 1,741; 78.9% response) and 12-year-old children (n = 2,367; 75.3% response) underwent a comprehensive eye examination, including cycloplegic autorefraction and ocular biometry. Astigmatism was determined in parents from spectacle prescriptions, which were supplied for 468 children. RESULTS: The prevalence of astigmatism in six-year-old children with astigmatic parents was not significantly different from that of those without astigmatic parents (6.8% vs 2.8%); corresponding rates for 12-year-old children were 9.5% and 7.8% (both P > .05). No significant differences in mean cylinder and in ocular biometric parameters were observed between children with astigmatic parents and those with no astigmatic parents. CONCLUSIONS: Parental astigmatism was not associated with a higher prevalence of childhood astigmatism and did not seem to have a significant impact on measures of ocular biometric parameters in children.

Ethnic differences in the impact of parental myopia: findings from a population-based study of 12-year-old Australian children.

PURPOSE: To examine the influences of ethnicity, parental myopia, and near work on spherical equivalent refraction (SER) and axial length (AL) in a population-based sample of 12-year-old Australian children. METHODS: Year-7 children in the Sydney Myopia Study (n = 2353, 75.3% response) underwent an ophthalmic examination including cycloplegic autorefraction (1% cyclopentolate) and ocular biometry (IOLMaster; Carl Zeiss Meditec GmbH, Jena, Germany). Data for parental myopia, ethnicity, near work, and outdoor activities were derived from questionnaires and were available for 1781 children. Optical prescriptions of parents were sought if the spectacles were used. RESULTS: The prevalence of myopia in the children increased with the number of myopic parents (7.6%, 14.9%, and 43.6% for no, one, or two myopic parents). In parallel, the mean SER (+/-SE of the mean) was more negative (0.70 +/- 0.08, 0.34 +/- 0.09, and -0.55 +/- 0.34 D), and the mean AL was longer (23.32 +/- 0.05, 23.44 +/- 0.06, and 23.62 +/- 0.16 mm) after adjustment for demographic and environmental factors. In multivariate analyses, odds of childhood myopia did not change with higher levels of near work (odds ratio [OR] = 1.01; 95% confidence interval [CI] = 0.99-1.03). Interactions between parental myopia and ethnicity were significant for SER and AL (both P < 0.0001), reflecting greater decreases in SER and greater increases in AL with the number of myopic parents in the children of East Asian ethnicity than in the children of European Caucasian ethnicity. In the nonmyopic children, there was no association between parental myopia and AL. CONCLUSIONS: In this sample, parental myopia was associated with more myopic SER and longer AL, with significant ethnic interactions.

Can information on the purpose of spectacle use and age at first use predict refractive error type?

PURPOSE: To assess the sensitivity and specificity of predicting refractive error type using information from a four-item questionnaire on the purpose of spectacle use and age at first use. METHODS: The Sydney Myopia Study examined 1,740 year 1 (78.9% response) and 2,353 year 7 students (75.3% response) from a random cluster sample of 34 primary and 21 secondary schools across Sydney. Parents of participants completed a four-item questionnaire that sought data on parental spectacle use, age at first use, and purpose of use (for clear distant vision, close work, or both). Prescriptions were obtained for 720 of 3,209 (22%) parents (73% of those approached) for validation. A receiver operating characteristic (ROC) curve was used to determine the optimal cutoff age for spectacle use in myopia classification. RESULTS: Using the ROC curve, a cutoff age of 30 years at first spectacle use produced the highest accuracy in determining myopia. We combined information on the purpose for using spectacles (for distant and near vision) and age of first use at 30 years or younger to determine myopia, otherwise hyperopia. Validated against prescriptions, the sensitivity and specificity of these predictions were 0.89 and 0.83, respectively, for myopia. The specificity was 0.92 for hyperopia and 0.80 for astigmatism, though corresponding sensitivities were lower at 0.23 and 0.46, respectively. CONCLUSIONS: In a sample of the parents of Sydney Myopia Study participants, information on the purpose of spectacle use with an age-at-first-use criterion can identify myopic refractive error with reasonable sensitivity and specificity. This four-item questionnaire may assist future epidemiological studies of screening for myopia.

Reproducibility of and effect of magnification on optical coherence tomography measurements in children.

PURPOSE: To determine the reproducibility of optical coherence tomography (OCT) measurements of macular thickness, peripapillary nerve fiber layer (NFL) thickness, and optic disk parameters and to investigate the effect of axial length and refractive error on these measurements in children with healthy eyes. DESIGN: Cross-sectional study. METHODS: The Sydney Childhood Eye Study examined 2,353 year 7 students (75.3% response) from a random cluster sample of 21 secondary schools across Sydney. A consecutive subsample of 120 children had OCT (StratusOCT, Carl Zeiss, Dublin, California, USA) performed by a single operator, which was repeated with a brief rest between the two sessions. Scans of the NFL, macula, and optic disk were performed. RESULTS: Intersubject variability of measurements of macular thickness, NFL thickness, and optic disk parameters assessed using intraclass correlation coefficients accounted for >85%, >62%, and >38% of total variability of measurements, respectively. Corresponding coefficients of variability were <5%, <8%, and <13%. Magnification effects attributable to axial length and refractive error on the measurement of these parameters were statistically not significant. CONCLUSION: The StratusOCT demonstrated reproducible measurements of macular and NFL thickness. Measurement of most optic disk parameters were also reproducible. Magnification attributable to axial length and refractive error had minimal impact on measurements of macular and NFL thickness.

Prevalence of eye disorders in young children with eyestrain complaints.

PURPOSE: To determine whether eyestrain symptoms predict eye conditions in 6-year-old children. DESIGN: Cross-sectional population-based study. METHODS: Reports of eyestrain symptoms were sought in parental questionnaires; 1740 children (79% response) underwent eye examinations (visual acuity, cover testing, cycloplegic autorefraction, and fundus examination). RESULTS: Eyestrain information was available for 1448 children; 220 (15.2%) reported eyestrain symptoms, including 60 (3.4%) who reported near work-associated headaches. Most children (82.3%) had a normal eye examination, while refractive errors, amblyopia, and strabismus were found in 15.0%, 3.6%, and 7.3%, respectively. Corresponding rates for children without eyestrain were 9.9%, 1.4%, and 1.8%, respectively. Moreover, 78.7% of children with refractive errors, 68% with amblyopia, and 58% with strabismus reported no eyestrain. CONCLUSIONS: Most children complaining of eyestrain had a normal eye examination; whereas most children with refractive error, amblyopia, or strabismus were free of eyestrain, making this complaint a poor marker of eye conditions in young children.

Factors associated with childhood strabismus: findings from a population-based study.

PURPOSE: To describe strabismus prevalence and associated factors in a representative sample of 6-year-old Australian children. DESIGN: Population-based cross-sectional study. PARTICIPANTS: One thousand seven hundred thirty-nine predominantly 6-year-old children resident in Sydney examined in 2003 and 2004. METHODS: Cover testing was performed at near and distance fixation, and with spectacles if worn. Logarithm of the minimum angle of resolution visual acuity was measured in both eyes before and after pinhole correction, after correcting any cylindrical refraction >0.50 diopters and with spectacles, if worn. Cycloplegic autorefraction (cyclopentolate) and detailed dilated fundus examination were performed. Each child's medical and perinatal histories were sought in a detailed parental questionnaire. MAIN OUTCOME MEASURES: Strabismus was defined as any heterotropia at near or distance fixation, or both, on cover testing. Microstrabismus was defined as a deviation of fewer than 10 prism diopters. RESULTS: Strabismus was diagnosed in 48 children (2.8% of the population), 5 of whom had previously undergone surgical correction; 26 children (54%) had esotropia, 14 (29%) had exotropia, 7 (15%) had microstrabismus, and 1 child had VIth cranial nerve palsy. Prematurity was associated with a 5-fold increase in the risk of esotropia (odds ratio, 5.0; 95% confidence interval, 1.8-14.1). Visual impairment (with presenting correction) was significantly more common in children with (22.9%) than without (1.3%) strabismus (P<0.0001). The presence of strabismus was significantly associated with hyperopia, astigmatism, anisometropia, and amblyopia (P<0.0001). CONCLUSIONS: This report documents the prevalence of strabismus and its relation to other ocular signs and visual impairment in a representative sample of Australian school children. Presence of strabismus was significantly associated with prematurity.