PURPOSE: To study safety of children's glasses in rural China, where fear that glasses harm vision is an important barrier for families and policy makers.DESIGN: Exploratory analysis from a clusterrandomized, investigator-masked, controlled trial.METHODS: Among primary schools (n [ 252) in western China, children were randomized by school to 1 of 3 interventions: free glasses provided in class, vouchers for free glasses at a local facility, or glasses prescriptions only (Control group). The main outcome of this analysis is uncorrected visual acuity after 8 months, adjusted for baseline acuity.RESULTS: Among 19 934 children randomly selected for screening, 5852 myopic (spherical equivalent refractive error £L0.5 diopters) eyes of 3001 children (14.7%, mean age 10.5 years) had VA £6/12 without glasses correctable to >6/12 with glasses, and were eligible. Among these, 1903 (32.5%), 1798 (30.7%), and 2151 (36.8%) were randomized to Control, Voucher, and Free Glasses, respectively. Intention-totreat analyses were performed on all 1831 (96.