Time Spent in Outdoor Activities in Relation to Myopia Prevention and Control: A Meta-Analysis and Systematic Review
Outdoor time is considered to reduce the risk of developing myopia.
The purpose is to evaluate the evidence for association between time outdoors and (1) risk of onset of myopia (incident/prevalent myopia); (2) risk of a myopic shift in refractive error and c) risk of progression in myopes only.
Of the 51 articles with relevant data, 25 were included in the meta-analysis and dose-response analysis.
Twenty-three of the 25 articles involved children.
With dose-response analysis, an inverse nonlinear relationship was found with increased time outdoors reducing the risk of incident myopia.
Also, pooled results from clinical trials indicated that when outdoor time was used as an intervention, there was a reduced myopic shift of -0.30 D (in both myopes and nonmyopes) compared with the control group after 3 years of follow-up.
However, when only myopes were considered, dose-response analysis did not find a relationship between time outdoors and myopic progression.
Increased time outdoors is effective in preventing the onset of myopia as well as in slowing the myopic shift in refractive error.
But paradoxically, outdoor time was not effective in slowing progression in eyes that were already myopic.
Further studies evaluating effect of outdoor in various doses and objective measurements of time outdoors may help improve our understanding of the role played by outdoors in onset and management of myopia.