Outdoor Activity and Myopia Progression in Children
Ophthalmology, August 2018
Building on evidence of the benefit of outdoor activity for prevention and control of myopia, Wu et al. implemented a program to encourage young Taiwanese schoolchildren to spend more time outside. After 1 year, those students who had been encouraged to spend at least 11 hours per week outdoors, with exposure to light intensity of at least 1,000 lux, had significantly less myopic shift and axial elongation than did those in the control group.
The study included 693 first graders at 16 schools. The intervention group (n = 267) participated in school-oriented outdoor activities, including fresh-air recess and summer learning assignments, and they were encouraged to spend at least 11 hours per week outside. The control group (n = 426) did not receive these interventions but spent some time outside. Both groups had outdoor exercise initiatives. All participants wore a light meter recorder and, with help from their parents, completed weekly activity diaries and questionnaires. Time outdoors was defined as the period during which light intensity was at least 1,000 lux according to the light meter. Outcomes of interest were changes in spherical equivalent and axial length from baseline to 1 year, as well as intensity and duration of exposure to outdoor light.
The researchers found that more students in the intervention group (50% vs. 23% of controls) spent more than 11 hours per week outdoors. Students who spent at least 200 minutes per week outside during school hours were found to have significantly less myopic shift with lux readings as follows: ≥1,000 lux, 0.14 D; ≥3,000 lux, 0.16 D. The intervention group had significantly less myopic shift than the control group (0.35 D vs. 0.47 D) and axial elongation (0.28 mm vs. 0.33 mm). The risk of rapid myopia progression was 54% lower in the intervention group (odds ratio, 0.46; p = .003). The protective effects against myopia were seen among myopic and nonmyopic children in the intervention group.
The authors concluded that exposure to strong sunlight may not be required for prevention of myopia. Longer periods of relatively low outdoor light intensity, as in the shade of trees, may be sufficient for the protective effect. Larger studies of longer duration are warranted. (Also see related commentary by Ian G. Morgan, BSc, PhD, in the same issue.)
The original article can be found here.