Have the child spend at least 2 hours outdoors each day — among unpaid, drug-free options, this is the only myopia-prevention method backed by randomized trials

An extra 40 minutes of outdoor class each day in grade 1 cut new myopia over three years from about four in ten to about three in ten. The health commission’s dose is at least 2 hours of daytime outdoor time a day, or 14 hours a week in total. Cloudy days count.

Cost

No money. But time must be cleared each day, often squeezed from homework and online classes. The hard part is doing it every day, not a few times.

Benefit

Grade-1 students in 12 Guangzhou primary schools were assigned by lot at school level (intervention schools 952 people, control schools 951, mean age 6.6 years). The intervention added one 40-minute outdoor activity class each school day and encouraged parents to take children out more after school. Over 3 years, new myopia was 30.4% in the intervention group (259 of 853 eligible) and 39.5% in controls (287 of 726). Difference −9.1 percentage points (95% CI −14.1 to −4.1, P<0.001); the true gap sits roughly between 4 and 14 percentage points fewer. Over 3 years, refractive progression (spherical equivalent change) was −1.42 D versus −1.59 D, a difference of 0.17 D (P=0.04). The intervention group progressed a little less. D is the unit for refractive power. Axial length (front-to-back eye length) growth did not differ between groups (P=0.07). Ten Core Knowledge Points for Preventing and Controlling Myopia in Children and Adolescents (防控儿童青少年近视核心知识十条) requires at least 2 hours of daytime outdoor activity a day, or 14 hours a week cumulative. It notes that even on cloudy days outdoor activity has a protective effect, and asks to avoid midday high heat and strong sun. Drug prevention of myopia also has lot-assigned trials. In Hong Kong, 474 children aged 4 to 9 without myopia were split into three groups and used eye drops once nightly for two years. With 0.05% atropine, myopia over two years was 28.4%; with placebo, 53.0%. With 0.01% atropine it was 45.9%, not different from placebo

Notes

This trial ran only 3 years, and participating children all started at age 6. A 9.1 percentage-point gap in myopia rates only keeps some children from becoming myopic; it does not guarantee no myopia. The same ten core points also give a few practices. Reading and writing: “one chi, one fist, one cun” (一尺一拳一寸). After 20 minutes of near work, look into the distance for 20 seconds or more. For primary and secondary students, non-study screen use should not exceed 15 minutes at a time or 1 hour a day in total. “Being outdoors” is not the same as “PE class”; standing outside at recess counts. Authors of the atropine trial say more trials are needed to confirm, and long-term safety still needs watching. Whether to use drops and at what strength, ask an eye doctor. The author found no other unpaid, drug-free method with a lot-assigned trial.

Sources · 3

1. He M, et al. (2015). Effect of Time Spent Outdoors at School on the Development of Myopia Among Children in China: A Randomized Clinical Trial. JAMA. doi.org/10.1001/jama.2015.10803
2. Yam JC, Zhang XJ, Zhang Y, et al. (2023). Effect of Low-Concentration Atropine Eyedrops vs Placebo on Myopia Incidence in Children: The LAMP2 Randomized Clinical Trial. JAMA, 329(6), 472-481. doi.org/10.1001/jama.2022.24162
3. 国家卫生健康委办公厅 (2023). 防控儿童青少年近视核心知识十条（国卫办妇幼函〔2023〕278 号）. gov.cn/zhengce/zhengceku/202307/content_68942…