Related Experiment Video
Updated: Apr 23, 2026
Binocular Dynamic Visual Acuity in Eyeglass-Corrected Myopic Patients
Published on: March 29, 2022
Effect of providing free glasses on children's educational outcomes in China: cluster randomized controlled trial
Xiaochen Ma1, Zhongqiang Zhou2, Hongmei Yi3
1Department of Agriculture and Resource Economics, University of California, Davis, Davis, CA, USA Stanford Center For International Development, Stanford University, Stanford, CA, USA ncongdon1@gmail.com.
Objective:
To assess the effect of provision of free glasses on academic performance in rural Chinese children with myopia.
Design:
Cluster randomized, investigator masked, controlled trial.
Setting:
252 primary schools in two prefectures in western China, 2012-13.
Participants:
3177 of 19,934 children in fourth and fifth grades (mean age 10.5 years) with visual acuity <6/12 in either eye without glasses correctable to >6/12 with glasses. 3052 (96.0%) completed the study.
Interventions:
Children were randomized by school (84 schools per arm) to one of three interventions at the beginning of the school year: prescription for glasses only (control group), vouchers for free glasses at a local facility, or free glasses provided in class.
Main Outcome Measures:
Spectacle wear at endline examination and end of year score on a specially designed mathematics test, adjusted for baseline score and expressed in standard deviations.
Results:
Among 3177 eligible children, 1036 (32.6%) were randomized to control, 988 (31.1%) to vouchers, and 1153 (36.3%) to free glasses in class. All eligible children would benefit from glasses, but only 15% wore them at baseline. At closeout glasses wear was 41% (observed) and 68% (self reported) in the free glasses group, and 26% (observed) and 37% (self reported) in the controls. Effect on test score was 0.11 SD (95% confidence interval 0.01 to 0.21) when the free glasses group was compared with the control group. The adjusted effect of providing free glasses (0.10, 0.002 to 0.19) was greater than parental education (0.03, -0.04 to 0.09) or family wealth (0.01, -0.06 to 0.08). This difference between groups was significant, but was smaller than the prespecified 0.20 SD difference that the study was powered to detect.
Conclusions:
The provision of free glasses to Chinese children with myopia improves children's performance on mathematics testing to a statistically significant degree, despite imperfect compliance, although the observed difference between groups was smaller than the study was originally designed to detect. Myopia is common and rarely corrected in this setting.Trial Registration Current Controlled Trials ISRCTN03252665.
