Visual Activity before and after the Onset of Juvenile Myopia

2011 
An association between near work and juvenile-onset myopia has long been theorized, but data in support of the association have shown small effects. Conflicting results have also been reported among studies and within individual studies using various measures of near work,1–4 leaving the issue unresolved. For example, the Singapore Cohort Study of Risk Factors for Myopia (SCORM) reported a significant difference in the number of books read per week by high myopes compared with low myopes and nonmyopes; however, the number of hours of reading per day did not differ among the three groups.1 An earlier cross-sectional report from the Orinda Longitudinal Study of Myopia (OLSM) found that more time was spent in near work (diopter-hours) by myopic children.3 Interestingly, while both SCORM and OLSM reported significant associations between various forms of near work and myopia in cross-sectional analyses of prevalent myopes, neither found any significantly increased risk of myopia onset associated with any form of near work in longitudinal analyses.5,6 The question arises as to whether children's near work activities change near or at the time of myopia onset, with different levels of activity for the premyope compared with that of the prevalent myope. There has not been a year-by-year longitudinal analysis of visual activity data before and after the onset of myopia. This question is relevant because selecting a single point in time, while informative, may miss pertinent information or a trend that depends on the time point(s) selected. Recent work showing less outdoor/sports activity in those who become myopic and in those whose myopia progresses makes assessing visual activity in this manner informative.6–8 Using methodology that we have applied in studying ocular component growth and myopia,9,10 we investigated differences in the visual activity profile between data from myopes and emmetropes before, at, and after the onset of myopia, by using growth curve models.
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