Assessing the prevalence of refractive errors and accuracy of vision screening by schoolteachers in Liberia

Tobi, Patrick ORCID logoORCID:, Ibrahim, Nazaradden, Bedell, Alex, Khan, Imran, Jolley, Emma and Schmidt, Elena (2022) Assessing the prevalence of refractive errors and accuracy of vision screening by schoolteachers in Liberia. International Health, 14 (Supp 1) . i41-i48. ISSN 1876-3413 [Article] (doi:10.1093/inthealth/ihab085)

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Evidence indicates that school-based vision screening by trained teachers is an effective way of identifying and addressing potential vision problems in schoolchildren. However, inconsistencies have been reported in both the testing methods and accuracy of the screeners. This study assessed the prevalence of refractive errors and accuracy of screening by teachers in Grand Kru County, Liberia.
We conducted a retrospective analysis of data from four schools where, in February 2019, children were screened for refractive errors by trained teachers and then re-examined by ophthalmic technicians. One row of five optotypes of the Snellen 6/9 (0.2 logMar) scale (tumbling E chart) was used at a distance of 3 m. The prevalence of visual impairment and associations with sex, age and school were explored. Sensitivity, specificity and predictive values were calculated.
Data were available for 823 of 1095 eligible children with a mean age of 13.7 y (range 5–18) and male:female ratio of 1:0.8. Poor vision was identified in 24 (2.9%) children with no differences by either sex or age but small differences by school. Screening by teachers had a sensitivity of 0.25 (95% confidence interval [CI] 0.077 to 0.423) and a specificity of 0.996 (95% CI 0.992 to 1.000). Positive and negative predictive values were 0.667 (95% CI 0.359 to 0.975) and 0.978 (95% CI 0.968 to 0.988), respectively. The results were influenced by a high number of misclassifications in one of the four schools.
Teachers can be trained to conduct vision screening tests on schoolchildren to an acceptable level of accuracy, but strong monitoring and quality assurance systems should be built into screening programmes from the onset. In settings like Liberia, where many children do not attend school regularly, screening programmes should extend to community platforms to reach children out of school.

Item Type: Article
Keywords (uncontrolled): Liberia, Refractive Error, Schoolchildren, Vision Screening, Humans, Vision, Low, Refractive Errors, Prevalence, Retrospective Studies, Adolescent, Child, Female, Male
Research Areas: A. > School of Science and Technology > Natural Sciences
Item ID: 34979
Notes on copyright: © The Author(s) 2022. Published by Oxford University Press on behalf of Royal Society of Tropical Medicine and Hygiene. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (, which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact
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Depositing User: Jisc Publications Router
Date Deposited: 19 Apr 2022 12:06
Last Modified: 09 May 2022 13:03

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