Intended for healthcare professionals

CCBYNC Open access

Effect of providing free glasses on children’s educational outcomes in China: cluster randomized controlled trial

BMJ 2014; 349 doi: (Published 23 September 2014) Cite this as: BMJ 2014;349:g5740
  1. Xiaochen Ma, graduate student12,
  2. Zhongqiang Zhou, graduate student3,
  3. Hongmei Yi, professor4,
  4. Xiaopeng Pang, professor5,
  5. Yaojiang Shi, professor6,
  6. Qianyun Chen, research assistant3,
  7. Mirjam E Meltzer, biostatistician3,
  8. Saskia le Cessie, professor78,
  9. Mingguang He, professor3,
  10. Scott Rozelle, professor9,
  11. Yizhi Liu, professor3,
  12. Nathan Congdon, professor310
  1. 1Department of Agriculture and Resource Economics, University of California, Davis, Davis, CA, USA
  2. 2Stanford Center For International Development, Stanford University, Stanford, CA, USA
  3. 3Key Laboratory of Ophthalmology and Division of Preventive Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
  4. 4Center for Chinese Agricultural Policy, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China
  5. 5School of Agricultural Economics and Rural Development, Renmin University of China, Beijing, China
  6. 6School of Economic Management, Xibei University, Xi’an, China
  7. 7Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, Netherlands
  8. 8Department of Medical Statistics and Bioinformatics, Leiden University Medical Center, Leiden, Netherlands
  9. 9Freeman Spogli Institute of International Studies, Stanford University, Stanford, CA, USA
  10. 10ORBIS International, New York, NY, USA
  1. Correspondence to: N Congdon, State Key Laboratory of Ophthalmology, and Translational Research in Equitable Eyecare, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China ncongdon1{at}
  • Accepted 6 September 2014


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.


  • Contributors: XCM and SR designed the study, collected and analyzed the data, and revised the manuscript. ZQZ, HMY, YJS, and QYC collected the data and revised the manuscript. XPP, MGH, and YL designed the study and revised the manuscript. MEM and SlC analyzed the data and revised the manuscript. NC designed the study, collected and analyzed the data, and wrote the manuscript. He is guarantor. All of the authors had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

  • Funding: This study was funded by OneSight (Mason, OH), Luxottica-China (Shanghai), Essilor-China(Shanghai), CLSA (Asia Pacific Markets; Hong Kong), Charity Aid Foundation (Sydney), and an anonymous donor (Hong Kong). NC is supported by a Thousand Man Plan grant from the Chinese government. The study sponsors had no role in study design; the collection, analysis, and interpretation of data; the writing of the report; or the decision to submit the paper for publication.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at and declare: the free glasses used in this study were supplied by OneSight, Luxottica-China, and Essilor-China, producers of frames and lenses in China who also provided financial support for the study; the authors have no other financial relationships with any organisations that might have an interest in the submitted work in the previous three years; and no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: This study was approved by the institutional review boards at Stanford University (Palo Alto, USA) and the Zhongshan Ophthalmic Center (Guangzhou, China). Permission was received from local boards of education in each region and the principals of all schools. The presented data are anonymized and risk of identification is low. The principles of the Declaration of Helsinki were followed throughout.

  • Data sharing: The full dataset and statistical code are available at with open access.

  • Transparency: NC (the manuscript’s guarantor) affirms that the manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 3.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:

View Full Text