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Kathryn A. Rose, Amanda French, Ian G. Morgan, Paul Mitchell; School-based Variation In The Prevalence Of Myopia: The Sydney Myopia Study. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2493.
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Numerous studies have shown that myopia prevalence varies between schools and academic streams. This relationship is explored in the Sydney Myopia Study(SMS).
SMS is a randomly selected cross-sectional study of 2 age samples from 34 primary and 21 high schools. All Year 1 (mean age 6.7 years) and Year 7 (mean age 12.7 years) students were invited to participate and 4,108 families gave informed consent. A comprehensive ocular examination included cycloplegic (1% cyclopentolate) autorefraction and spherical equivalent was calculated for the right eye. Details of lifestyle and environmental factors were ascertained by questionnaire. Measures of a school’s academic achievement were obtained from the National Assessment Program for Literacy and Numeracy, an exam performed by students across Australia and from the average percentage of high school students obtaining a mark in the top 10% of the state-wide Higher School Certificate over a 3 year period.
The prevalence of myopia in high schools ranged from 2.7-59.2% (mean 11.87% ±12.1) and in primary schools 0-7.1% (mean 1.5% ±2.04). The two high schools with the highest prevalence of myopia were academically selective and measures of academic achievement were strongly correlated with the prevalence of myopia in the high schools (all correlations, r >0.78), but not primary schools. Mean time spent in near work within a school was correlated with academic achievement (r = 0.78) and myopia (r = 0.69), while mean time spent outdoors was negatively correlated with the proportion of children in the school who had myopia (r = -0.69). The proportion of children in a school who were from outside the normal geographical enrollment area of that school was also correlated to the prevalence of myopia in the high schools (r = 0.61) but not primary schools.
Previously we have shown that for individuals time spent on near work was not significantly correlated with myopia yet at the school level this association was strong. These results suggest that the variation of the prevalence of myopia found between schools is, in part, linked to the aspirations of students and their parents for high academic achievement, associated with study habits involving both high levels of close work, and little time spent outdoors. It is likely that the patterns of behavior are established prior to entry to high school. These findings emphasize that care must be taken to obtain a representative population when sampling from schools.
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