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Ian G. Morgan, Fan Xiang, Kathryn A. Rose, Qianyun Chen, Mingguang He; Two Year Results from the Guangzhou Outdoor Activity Longitudinal Study (GOALS). Invest. Ophthalmol. Vis. Sci. 2012;53(14):2735.
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Increased time spent outdoors has been reported to be a protective factor against the development of myopia in both cross-sectional and longitudinal studies. This effect has been shown to be due to time spent out of doors rather than engagement in sports activities, and the postulated mechanism, light-stimulated release of retinal dopamine which inhibits eye growth, has received support from animal studies. We have established a school-based intervention to promote time spent outdoors, and baseline, one and two year data have now been collected.
Schools were matched for unaided visual acuity loss during the primary school years and randomly assigned to the control and intervention arms. All children enrolled in Grade 1 (ages 6-7) were invited to participate. In control schools, children carried out a normal pattern of activity, but in the intervention schools, children received an additional class after school in which they were involved in structured outdoors activities. Cycloplegic refraction, axial length and corneal curvature were measured at baseline and after one and two years. Schools were randomly visited by study staff and inspectors from the Department of Education to ensure compliance.
At baseline, there were no differences between control and intervention groups in mean SER, axial length or prevalence of myopia. Over the two year period, refraction (mean±SD) in the control arm decreased by 0.86±0.77D compared to 0.75±0.69D (p<0.01) in the intervention arm. Changes in AL were also different between arms (0.61±0.35mm vs 0.59±0.33mm, p<0.05). The prevalence of myopia increased from 4.3% in the control arm at baseline compared to 3.5% in the intervention arm (p=0.35) to 12.6% and 9.0% respectively at one year (p <0.05), and 25.2% and 20.7% (p<0.05).
While the differences between groups in changes in mean SER, AL and prevalence of myopia are small, there is a consistent pattern of less axial elongation and development of myopia in the intervention arm which suggests that the intervention is having some effect. However, the effects are very small, consistent with a meta-analysis of studies of the protective effect of time outdoors. These data provide "proof-of-principle" evidence for the effectiveness of the intervention, but suggest that greater exposures will be required to obtain clinically significant effects.
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