Outdoor activity during class recess prevents myopia onset and shift in premyopic children: Subgroup analysis in the recess outside classroom study.

Objective: To investigate whether premyopia is a risk factor for myopia onset and whether outdoor activities can protect against myopia development in premyopic children in the Recess Outside Classroom (ROC) study.

Methods: Nonmyopic schoolchildren aged 7-11 years were recruited from two schools in Taiwan. One school implemented the ROC program, which encouraged children to go outdoors during recess. The control school maintained its usual schedule. A cycloplegic autorefraction was performed. Premyopia was defined as spherical equivalent refraction ≤ +0.75 diopters (D) and > -0.50 D.

Results: After one year of follow-up, multivariate logistic analysis revealed that the ROC program reduced the risk of myopia onset by 61 % (odds ratio [OR] = 0.39, 95 % confidence interval [CI]: 0.21-0.70, P = 0.002). However, premyopia status increased the risk of myopia onset by 14 times compared to hyperopic status (OR = 14.0, 95 % CI: 1.86-105.3, P = 0.010). In the subgroup analysis of premyopic children, the myopic shift was also significantly lower in the ROC group than in the control group (-0.20 ± 0.60 D/year vs. -0.40 ± 0.66 D/year, P = 0.017). Myopia incidence in premyopic children was significantly lower in the ROC group than in the control group (19.6 % vs. 37.8 %, P = 0.001). Multivariate regression analysis showed that participation in the ROC program was significantly associated with a lower myopic shift in premyopic children (-0.22 D/year, 95 % CI: -0.39 to -0.06, P = 0.008)

Conclusions: Premyopia is a risk factor for myopia onset. A school policy that includes more outdoor time can effectively prevent myopia onset and shift in premyopic children.