Purpose: 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.
Methods: 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.
Results: 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).
Conclusion: 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 201426(3):121-8 © 2014 by the Iranian Society of Ophthalmology