Pilot trial to determine the reliability of the snellen chart for assessment of the visual acuity in young people

Abstract

The visual acuity is the main characteristic evaluated to know how a person sees. For the visual acuity measuring it is used the letter chart, in Colombia the most used it is the Snellen Chart. <em><strong>Objective:</strong></em> To determinate the reliability inter e intraevaluator of Snellen Chart to test visual acuity. <em><strong>Methods:</strong></em> With convenience sampling two evaluators tested visual acuity with serif Snellen Chart to 110 subjects (220 eyes) who were university students between 15-30 years old, full distance refractive correction, normal binocular vision, and no pathologies of anterior and posterior of eye. A refractive error (myopia 1.50D) was induced for all the subjects and the trials were carrying out. <em><strong>Results:</strong></em> Visual acuity means was -0.06 (20/20+5), with induced myopia 0.51 (20/63). Wilcoxon sign rank test showed difference between inter evaluators (p=0,0001; p=0,007) in first trial and wearing plus lens +1.50D between inter evaluators in both trials ((p=0,03; p=0,001). Conclusions: Correlation Coefficient and Concordance of Lin showed a poor concordance and a moderated-high variability in the outcomes; then, Snellen chart has a poor concordance and moderate variability, so we suggest achieving researches about the validity of this test in the population with normal and subnormal vision.