Validity of Uncorrected Visual Acuity Measured in Vision Screening Programs for Detecting Refractive Errors

Uncorrected visual acuity is the only variable measured in vision screening programs in many countries worldwide. The aim of this study was to calculate the sensitivity, specificity, and predictive value of the uncorrected visual acuity in the screening programs for the diagnosis of refractive errors. In this cross-sectional study, of 4,157 students in the first year of primary school who were selected from seven cities of Iran through multistage cluster sampling, 3,675 students participated in the study. In each school, measurement of corrected and uncorrected visual acuity, cycloplegic and non-cycloplegic refraction, and cover test were performed for all students by an optometrist. Refractive errors obtained by cycloplegic refraction were considered gold standard and the validity of uncorrected visual acuity measured in the screening program for the diagnosis of refractive error was calculated. In students with visual acuity of 20/20, the prevalence of myopia, hyperopia and astigmatism was 1.14%, 8.07% and 11.11%, respectively. The sensitivity of uncorrected visual acuity in the screening program for the diagnosis of myopia, hyperopia, astigmatism, and ametropia was 25.33%, 12.81%, 14.34%, and 12.64%. The area under the ROC curve of uncorrected visual acuity by optometrist and the screening program only showed a significant difference in myopia (p=0.013). The measurement of visual acuity in screening programs is not useful per se in the diagnosis of refractive errors and has a high percentage of false negative results. Adding refractive error examinations to the protocol of screening programs can increase their efficacy.Iranian Journal of Ophthalmology 2014;26(3):121-8 © 2014 by the Iranian Society of Ophthalmology