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Better Vision for Better Learning?: Evidence from a Randomized Controlled Trial in Vietnam
Last registered on September 28, 2020

Pre-Trial

Trial Information
General Information
Title
Better Vision for Better Learning?: Evidence from a Randomized Controlled Trial in Vietnam
RCT ID
AEARCTR-0006533
Initial registration date
September 27, 2020
Last updated
September 28, 2020 11:41 AM EDT
Location(s)
Region
Primary Investigator
Affiliation
Harvard University
Other Primary Investigator(s)
PI Affiliation
University of Minnesota
PI Affiliation
Yonsei University
Additional Trial Information
Status
Completed
Start date
2016-10-14
End date
2017-12-06
Secondary IDs
Abstract
Vietnam is a country where eye health care infrastructure is inferior to its economic growth and income level. The eye health care for children is especially limited in Vietnam: around one-fifth of the children under 15 years old are suffering from uncorrected refractive errors. Uncorrected refractive errors at school age are not only a vision problem, but also may affect school achievement that ultimately may have a significant impact on labor market outcomes and poverty. This paper presents the effect of vision screening and free eyeglasses on children's academic performance at school in Thanh Hoa province, Vietnam. We use a school-level cluster randomized controlled trial to evaluate providing vision screening and free eyeglasses to primary school students in Grades 4 and 5. We find that approximately 10.7 percent and 9.6 percent of grade 4 and 5 students suffer from vision impairment and uncorrected refractive errors in Thanh Hoa province. Furthermore, while 27 percent of students with refractive errors already had eyeglasses, only 29 percent of them had appropriate eyeglasses. We also find that providing vision screening and free eyeglasses successfully increases children's test scores. The magnitude of the impact ranges from 0.16 to 0.22 standard deviations for reading test scores, 0.16 to 0.23 standard deviations for mathematics test scores, and 0.14 to 0.26 standard deviations for total test scores after one year of providing eyeglasses. This paper also provides heterogenous effect of enhancing low vision on students' test score by gender and vision impairment level.
External Link(s)
Registration Citation
Citation
Glewwe, Paul, Jongwook Lee and Sangchul Yoon. 2020. "Better Vision for Better Learning?: Evidence from a Randomized Controlled Trial in Vietnam." AEA RCT Registry. September 28. https://doi.org/10.1257/rct.6533-1.0.
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Experimental Details
Interventions
Intervention(s)
All grade 4 and 5 students in 140 schools in Vietnam receive free school-based vision screening. Vision-impaired students, who need eyeglasses, in the treatment schools receive a pair of free eyeglasses immediately while those in the control schools receive free eyeglasses after one year.
Intervention Start Date
2016-10-14
Intervention End Date
2017-12-06
Primary Outcomes
Primary Outcomes (end points)
Reading (Vietnamese) and mathematics test scores
Primary Outcomes (explanation)
Secondary Outcomes
Secondary Outcomes (end points)
Secondary Outcomes (explanation)
Experimental Design
Experimental Design
140 primary schools in Thanh How province in Vietnam are randomly selected proportionally based on the number of schools in each district. The 140 schools are paired based on the school size in each district. One school in each pair is randomly assigned to the treatment group, and the other school in each pair is assigned to the control group. Thus, 70 treatment schools and 70 control schools are randomly selected, stratified by district and school size.

A two-step school-based vision screening is implemented for all students in 140 primary schools. Vision-impaired students, who need eyeglasses, in grades 4 and 5 in 70 treatment schools receive a pair of free eyeglasses after the vision screening, and those students in 70 control schools receive a pair of free eyeglasses after one year of the screening. Baseline reading and mathematics tests are conducted with the school-based vision screening, and endline tests are administered one year later.

This study estimates the effect of providing eyeglasses using intention-to-treat (ITT) analysis by comparing the mean outcomes of students in the treatment schools with the mean outcomes of those in the control schools.
Experimental Design Details
Randomization Method
Randomization done in office by a computer from a list of all primary schools in Thanh Hoa province, Vietnam. First, 140 schools were randomly selected. Second, schools were paired based on the school size within each district. Third, one treatment school and one control school were randomly selected from each pair.
Randomization Unit
School-level clustered randomization is used.
Was the treatment clustered?
Yes
Experiment Characteristics
Sample size: planned number of clusters
140 schools
Sample size: planned number of observations
4,200 students
Sample size (or number of clusters) by treatment arms
70 treatment schools and 70 control schools
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
With a sample of 140 schools (70 treatment schools and 70 control schools) and 30 students per school, ensuring power=0.8 and alpha=0.05, the standardized minimum detectable effect size is 0.1706 SD with ICC = 0.1, 0.2253 SD with ICC = 0.2, and 0.2691 SD with ICC = 0.3, assuming 100% take-up rate.
IRB
INSTITUTIONAL REVIEW BOARDS (IRBs)
IRB Name
Study has received IRB approval. Details not available.
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
December 06, 2017, 12:00 AM +00:00
Is data collection complete?
Yes
Data Collection Completion Date
December 06, 2017, 12:00 AM +00:00
Final Sample Size: Number of Clusters (Unit of Randomization)
140 schools

All 140 schools received free school-based vision screening and free eyeglasses, but one treatment school was refused to participate in the data collection. The refused treatment school was excluded from the analysis, and one paired control school was also excluded from the analysis. Thus, the final sample size used in the data analysis is 138 schools (69 treatment schools and 69 control schools).
Was attrition correlated with treatment status?
No
Final Sample Size: Total Number of Observations
23,474 students were participated in the vision screening, and 3,520 students participated in the data collection (baseline and endline reading and mathematics tests).
Final Sample Size (or Number of Clusters) by Treatment Arms
69 treatment schools and 69 control schools
Data Publication
Data Publication
Is public data available?
No
Program Files
Program Files
No
Reports, Papers & Other Materials
Relevant Paper(s)
REPORTS & OTHER MATERIALS