Effect of Time Spent Outdoors at School on the Development of Myopia Among Children in China: A Randomized Clinical Trial

  • The objective of this study is to assess the efficacy of increasing time spent outdoors at school in preventing incident myopia.

  • The study selected a cluster randomized trial of children in grade 1 (6 year old) from 12 primary schools in Guangzhou, China.

  • The study measured the 3-year cumulative incidence rate of myopia  among the students without established myopia at baseline and the changes in spherical equivalent refraction and axial length among all students.

  • There were 952 children in the intervention group and 951 in the control group with a mean (SD) age of 6.6 (0.34) years. The cumulative incidence rate of myopia was 30.4% in the intervention group and 39.5% in the control group.

  • There was also a significant difference in the 3-year change in spherical equivalent refraction for the intervention group  compared with the control group.

  • Elongation of axial length was not significantly different between the intervention group (0.95 mm) and the control group (0.98 mm).

  • The addition of 40 minutes of outdoor activity at school compared with usual activity resulted in a reduced incidence rate of myopia over the next 3 years.

  • Further studies are needed to assess long-term follow-up of these children and the generalizability of these findings.

Publication date

April 9, 2019


JAMA Ophthalmology


Mingguang He, MD, PhD,; Fan Xiang, MD, PhD,; Yangfa Zeng, MD; et al
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