Importance of including refractive error tests in school children's vision screening.

BACKGROUND: This study determined the importance of including tests for refractive errors in vision screening. METHODS: In this cross-sectional study, we performed a random cluster sampling of schoolchildren in the city of Dezful, Iran. After sampling and obtaining informed written consents from their parents, children underwent examinations at the school sites. Students underwent tests of visual acuity, cover tests and cycloplegic refractions. Elementary and middle school students who had a visual acuity of 20/20 or better in both eyes were included in the study. RESULTS: From 3673 elementary and middle school students, 2957 (80.5%) had 20/20 vision or better. Of these, 16.1% [95% confidence interval (CI): 14.8 - 17.4] were ametropic, 0.4% had myopia and 10.1% had hyperopia. Mean sphere in those with hyperopia was +2.6±0.7 (range: +2.0 to +7.28) diopter (D). Astigmatism was detected in 6.6% and the mean cylinder was -0.9 (range: -0.75 to -3.25) D. The rate of anisometropia was 1.5% (95% CI: 0.8 - 2.0). CONCLUSION: Screening results of 20/20 vision for schoolchildren does not necessarily indicate normal eye status because hyperopia and astigmatism may still be sources of visual discomfort. To identify these cases and increase the sensitivity of screening tests, measurement of refractive errors by cycloplegic refraction tests might be included in vision screening.