In August 2019 researchers from China published the results of their review of the medical scientific literature to assess whether spending time outdoors helps protect against near/short sightedness. A total of 5 studies, involving 3,014 children (aged 6-12 years), met the inclusion criteria of accepting that outdoor activity was a preventative measure for near/short sightedness and were included in the review. The degree of near /short sightedness was assessed at the beginning and end of the studies which had a follow up period of between 9-36 months. At the start of the studies the degree of near/short sightedness was greater in the outdoor groups compared to the control groups. Results showed that at the end of the study periods, the changes in near/short sightedness were smaller and that there were fewer new cases in the outdoor groups than in the control groups.
Cao K et al. Significance of Outdoor Time for Myopia Prevention: A Systematic Review and Meta-Analysis Based on Randomized Controlled Trials. Ophthalmic Res. 2019 Aug 20:1-9.