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The Impact of Eyeglasses on the Academic Performance of Primary School Students in China
Last registered on June 27, 2016

Pre-Trial

Trial Information
General Information
Title
The Impact of Eyeglasses on the Academic Performance of Primary School Students in China
RCT ID
AEARCTR-0001336
Initial registration date
June 27, 2016
Last updated
June 27, 2016 1:19 PM EDT
Location(s)
Primary Investigator
Affiliation
University of Minnesota
Other Primary Investigator(s)
PI Affiliation
Hong Kong University of Science and Technology
PI Affiliation
University of Tokyo
Additional Trial Information
Status
Completed
Start date
2004-06-01
End date
2005-06-01
Secondary IDs
Abstract
About 10% of primary school students in developing countries have poor vision, but very few of them wear glasses. Almost no research examines the impact of poor vision on school performance, and simple OLS estimates could be biased because studying harder may adversely affects one’s vision. This paper presents results from a randomized trial in Western China that offered free eyeglasses to rural primary school students. Our preferred estimates, which exclude township pairs for which students in the control township were mistakenly provided eyeglasses, indicate that wearing eyeglasses for one academic year increased the average test scores of students with poor vision by 0.16 to 0.22 standard deviations, equivalent to 0.3 to 0.5 additional years of schooling. These estimates are averages across the two counties where the intervention was conducted. We also find that the benefits are greater for under-performing students. A simple cost-benefit analysis suggests very high economic returns to wearing eyeglasses, raising the question of why such investments are not made by most families. We find that girls are more likely to refuse free eyeglasses, and that parental lack of awareness of vision problems, mothers’ education, and economic factors (expenditures per capita and price) significantly affect whether children wear eyeglasses in the absence of the intervention.
External Link(s)
Registration Citation
Citation
Glewwe, Paul, Albert Park and Meng Zhao. 2016. "The Impact of Eyeglasses on the Academic Performance of Primary School Students in China." AEA RCT Registry. June 27. https://doi.org/10.1257/rct.1336-1.0.
Former Citation
Glewwe, Paul, Albert Park and Meng Zhao. 2016. "The Impact of Eyeglasses on the Academic Performance of Primary School Students in China." AEA RCT Registry. June 27. https://www.socialscienceregistry.org/trials/1336/history/9081.
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Experimental Details
Interventions
Intervention(s)
Intervention Start Date
2004-09-01
Intervention End Date
2005-06-01
Primary Outcomes
Primary Outcomes (end points)
Average Test Scores (Both Counties)

Average Test Scores (County 1)

Average Test Scores (County 2)

Subject Test Scores (County 1 only): Chinese

Subject Test Scores (County 1 only): Math

Subject Test Scores (County 1 only): Science
Primary Outcomes (explanation)
Secondary Outcomes
Secondary Outcomes (end points)
Secondary Outcomes (explanation)
Experimental Design
Experimental Design
A randomized control trial was administered in two counties in rural China in 2004 to examine the impact of providing eyeglasses to students in grades 4-6 with poor vision. The townships were randomly divided between treatment and comparison groups, in which either all or none of the township' s schools received eyeglasses. At the end of the 2003-2004 school year, a baseline survey was conducted which collected data on student characteristics, academic test scores, and visual acuity in both treatment and comparison schools. Free eyeglasses were offered to students with poor vision in treatment schools who would be entering grades 4-6 in the fall of 2004. At the end of 2004-2005 academic year, grades for the fall and spring semesters were collected to evaluate the impact of the eyeglasses on test scores.
Experimental Design Details
Randomization Method
In County 1 and County 2, all included townships were ranked by income per capita in 2003. Starting with the first two townships (the two wealthiest), one was randomly assigned to be a treated township and the other was assigned to the control group; this was repeated for all subsequent township pairs. In county 1, the 19th township (the poorest) was not paired with another township; it was randomly assigned to the treatment group. In each township primary schools were either all assigned to the treatment group or all assigned to the control group.
Randomization Unit
individual townships
Was the treatment clustered?
Yes
Experiment Characteristics
Sample size: planned number of clusters
19 townships in County 1

18 townships in County 2
Sample size: planned number of observations
approximately 29,000 schoolchildren
Sample size (or number of clusters) by treatment arms
Control:

9 townships in County 1

9 townships in County 2

Treatment:

10 townships in County 1

9 townships in County 2
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
IRB
INSTITUTIONAL REVIEW BOARDS (IRBs)
IRB Name
University of Minnesota Institutional Review Board
IRB Approval Date
Details not available
IRB Approval Number
Details not available
Post-Trial
Post Trial Information
Study Withdrawal
Intervention
Is the intervention completed?
Yes
Intervention Completion Date
June 01, 2005, 12:00 AM +00:00
Is data collection complete?
Yes
Data Collection Completion Date
June 01, 2005, 12:00 AM +00:00
Final Sample Size: Number of Clusters (Unit of Randomization)
25 townships (12 dropped due to implementation problems)
Was attrition correlated with treatment status?
No
Final Sample Size: Total Number of Observations
18,902 students
Final Sample Size (or Number of Clusters) by Treatment Arms
12 townships treatment 12 townships control
Data Publication
Data Publication
Is public data available?
Yes
Program Files
Program Files
Yes
Reports and Papers
Preliminary Reports
Relevant Papers
Abstract
About 10% of primary school students in developing countries have poor vision, but very few of them wear glasses. Almost no research examines the impact of poor vision on school performance, and simple OLS estimates could be biased because studying harder may adversely affects one’s vision. This paper presents results from a randomized trial in Western China that offered free eyeglasses to rural primary school students. Our preferred estimates, which exclude township pairs for which students in the control township were mistakenly provided eyeglasses, indicate that wearing eyeglasses for one academic year increased the average test scores of students with poor vision by 0.16 to 0.22 standard deviations, equivalent to 0.3 to 0.5 additional years of schooling. These estimates are averages across the two counties where the intervention was conducted. We also find that the benefits are greater for under-performing students. A simple cost-benefit analysis suggests very high economic returns to wearing eyeglasses, raising the question of why such investments are not made by most families. We find that girls are more likely to refuse free eyeglasses, and that parental lack of awareness of vision problems, mothers’ education, and economic factors (expenditures per capita and price) significantly affect whether children wear eyeglasses in the absence of the intervention.
Citation
Glewwe, Paul, Albert Park, and Meng Zhao. 2016. "A Better Vision for Development: Eyeglasses and Academic Performance in Rural Primary Schools in China." Journal of Development Economics 122:170-182.