Comparative Effect of Cylindrical Lenses Versus Spherical Equivalent on Contrast Sensitivity

Abstract

Background: Astigmatism is a common refractive error that affects visual acuity and contrast sensitivity. Cylindrical lenses and spherical equivalents are commonly prescribed to correct these errors, but their comparative effects on contrast sensitivity are not well-documented.Objective: To compare the effects of cylindrical lenses versus spherical equivalents on contrast sensitivity in individuals with astigmatism.Methods: A randomized controlled trial was conducted involving 68 participants with astigmatism, aged 15 to 30 years. Participants were randomly assigned to receive either cylindrical lens correction or spherical equivalent correction. Contrast sensitivity was measured using the Pelli-Robson chart at baseline and during two follow-ups over three months. Data were analyzed using Friedman's Two-Way Analysis of Variance and the Wilcoxon Signed Ranks Test, with p ≤ 0.05 considered statistically significant.Results: The mean contrast sensitivity decreased from 1.95 ± 0.07 to 1.93 ± 0.09 over three months. Cylindrical lenses resulted in higher contrast sensitivity scores (2.00 in 67.6% of cases at final visit) compared to spherical equivalents (44.1%, p < 0.001).Conclusion: Cylindrical lenses significantly improve contrast sensitivity compared to spherical equivalents, particularly in moderate to high astigmatism.