Time Outdoors in Reducing Myopia: A School-Based Cluster Randomized Trial with Objective Monitoring of Outdoor Time and Light Intensity

This study evaluates the efficacy of time outdoors per school day over 2 years on myopia onset and shift.

The research focused on a total of 6295 students aged 6 to 9 years from 24 primary schools in Shanghai, China, stratified and randomized by school in a 1:1:1 ratio to control (n = 2037), test I (n = 2329), or test II (n = 1929) group.


An additional 40 or 80 minutes of outdoor time was allocated to each school day for test I and II groups. Children in the control group continued their habitual outdoor time. Objective monitoring of outdoor and indoor time and light intensity each day was measured with a wrist-worn wearable during the second-year follow-up.

Increasing outdoor time reduced the risk of myopia onset and myopic shifts, especially in nonmyopic children. The protective effect of outdoor time was related to the duration of exposure and light intensity. The dose–response effect between test I and test II was not observed probably because of insufficient outdoor time achieved in the test groups, which suggests that proper monitoring on the compliance on outdoor intervention is critical if one wants to see the protective effect.

Publication date

November 2, 2022


Journal of Ophthalmology


Xiangui He PhD; Padmaja Sankaridurg PhD; Jingjing Wang PhD; Jun Chen PhD; Thomas Naduvilath; Mingguang He, PhD; Zhuoting Zhu PhD; Wayne Li MD; Ian G. Morgan MD; Shuyu Xiong PhD; Jianfeng Zhu MD; Haidong Zou MD; Kathryn A. Rose, MD; Bo Zhang MS; Rebecca Weng, GD; Serge Resnikoff MD; Xun Xu M
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