PARC Working Paper Series

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Working Paper

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Hannum, E. & Zhang, Y. 2012. Poverty and Proximate Barriers to Learning: Vision Deficiencies, Vision Correction and Educational Outcomes in Rural Northwest China. World Development, 40(9), 1921-1931. DOI: 10.1016/j.worlddev.2012.04.029


Few studies of educational barriers in developing countries have investigated the role of children’s vision problems, despite the self-evident challenge that poor vision poses to classroom learning and the potential for a simple ameliorative intervention. We address this gap with an analysis of two datasets from Gansu Province, a highly impoverished province in northwest China. One dataset is the Gansu Survey of Children and Families (GSCF, 2000 and 2004), a panel survey of 2,000 children in 100 rural villages; the other is the Gansu Vision Intervention Project (GVIP, 2004), a randomized trial involving 19,185 students in 165 schools in two counties. Results attest to significant unmet need for vision correction. About 11 percent of third to fifth graders in the GVIP and about 17 percent of 13 to 16 year olds in the GSCF had diagnosed vision problems. Yet, just 1 percent of the GVIP sample and 7 percent of the GSCF sample wore glasses in 2004, and access to vision correction shows a sharp socioeconomic gradient in both datasets. Importantly, vision problems themselves are actually selective of higher socioeconomic status children and more academically engaged students, a finding that poses challenges to isolating the causal impact of glasses-wearing. Propensity score matching estimates based on the GSCF suggest a significant effect of glasses-wearing on standardized math and literacy tests, though not on language tests. Analysis of the GVIP intervention shows that those who received glasses were less likely to fail a class. While we cannot firmly rule out all sources of selectivity, findings are consistent with the commonsense notion that correcting vision supports learning. The high level of unmet need for vision correction, together with evidence suggesting that wearing glasses supports learning, indicates the potential value of this simple intervention for students in developing country settings. The selectivity issues involved in the analysis indicate the need for further empirical studies that test the impact of vision correction on learning.


China, Children, Education, Vision, Health, Developing countries, Poverty, Eyeglasses



Date Posted: 05 August 2008