Study Design, Setting, and Participants
This unblinded, noninferiority, cluster RCT was conducted in Yudu County, Jiangxi Province, China. Baseline examinations were completed in October 2020, and a follow-up visit at the end of 1 academic year was completed in June 2021. All examinations were performed by the same study examiners using the same protocol and equipment. All study examiners (including D.W., R.X., J.Z., X.H., and S.C.) were qualified optometrists, ophthalmologists, or teachers. The trial protocol is provided in A total of 24 elementary schools (12 rural and 12 urban) with a mean class size of more than 30 children and sufficient conditions for 2 or more classes to play sports at the same time were invited and agreed to participate. One class each in grades 3 and 4 was randomly selected. Children were between ages 7 and 11 years. Children were excluded if they were unable to participate on 2 or more school days or were unsuitable for physical activity due to health or physical restrictions.