Outdoor activities with relatively low light exposure may reduce myopic shift
The school-based outdoor promotion programme appears to effectively reduce the myopia change in both myopic and nonmyopic children, with longer time outdoors with lower light intensity, such as in hallways or under trees, exerting a favourable effect, according to a study from Taiwan.
A total of 693 grade 1 schoolchildren were randomly assigned to the intervention group (n=267) or the control group (n=426). Children in the intervention group were encouraged to go outdoors for up to 11 hours weekly. Data collection included eye examinations, cycloplegic refraction, noncontact axial length measurements, light meter recorders, diary logs and questionnaires.
Main outcomes investigated were more favourable in the intervention vs control group. Specifically, the children in the intervention group showed significantly less myopic shift and axial elongation (0.35 vs 0.47 dioptre; p=0.002; 0.28 vs 0.33 mm; p=0.003). Moreover, the risk of myopia progression was 54-percent lower (odds ratio, 0.46; 95 percent CI, 0.28–0.77; p=0.003).
The benefits obtained with the intervention were significant in both nonmyopic and myopic children compared with controls.
Regarding spending outdoor time of at least 11 hours weekly with exposure to ≥1,000 lux of light, the number of participants was significantly higher in the intervention group than in the control group (49.79 percent vs 22.73 percent; p<0.001).
In schoolchildren with longer outdoor time in school (≥200 minutes), myopic shift was significantly reduced (measured by light meters; ≥1000 lux: 0.14 dioptre; 95 percent CI, 0.02–0.27; p=0.02; ≥3000 lux: 0.16 dioptre; 95 percent CI, 0.002–0.32; p=0.048).
The findings suggest that longer duration of relatively lower outdoor light intensity activity, such as in hallways or under trees, can be considered in the prevention of myopia, researchers said. Moreover, outdoor activities with strong sunlight exposure may not be necessary.