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D. O. Mutti, L. T. Sinnott, L. A. Jones-Jordan, S. A. Cotter, R. N. Kleinstein, R. E. Manny, J. D. Twelker, K. Zadnik, CLEERE Study Group; Time Outdoors, Near Work, and the Progression of Myopia in Children. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2968.
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Several studies have shown that myopic children spend less time outdoors than non-myopic children. We have also shown that more time spent outdoors by non-myopic children is associated with a reduction in the risk of myopia onset (Jones et al., IOVS, 2007). We investigated whether time spent outdoors or performing near work is related to the rate of myopia progression in children.
Subjects were 840 myopic participants in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study who returned for at least one subsequent annual visit and had a parent-completed survey of near work and time spent outdoors. Refractive error was measured by autorefraction (Canon R-1, Grand Seiko WR-5100K) under cycloplegia (tropicamide or tropicamide plus cyclopentolate). Multilevel, repeated-measures linear regression models were fitted to determine the effect of time outdoors and near work on the annual refractive error change. Covariates in all models included age, gender, ethnicity, study site, and autorefractor type.
There were no significant main effect model associations between myopia progression and either time outdoors or near work (p = 0.23 and p = 0.65, respectively; the 95% CI for each estimated slope was less than ±0.005). A more detailed analysis showed a significant gender-by-activity interaction for both time outdoors and near work (p = 0.039 and p = 0.0005, respectively, for the interactions). These interactions were comprised of statistically significant but clinically meaningless associations between myopia progression and time outdoors for girls (0.005 D per year less progression per hour spent outdoors each week) and near work for boys (-0.0015 D per year more progression per hour spent in near work each week).
Activities such as being outdoors or performing near work appear to have no meaningful influence on the rate of myopia progression. The protective effects of time outdoors associated with a reduction in the risk of myopia onset may only apply to non-myopic eyes before onset. Alternatively, this protective effect may influence some factor related to the risk of myopia onset that is not directly related to the rate of ocular axial elongation and, therefore, not directly related to the rate of myopia progression.
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