The effect of response biases on resolution thresholds of Sloan letters in central and paracentral vision

Abstract

PurposeLetter resolution depends on three factors: perceivability, response bias, and similarity. The aim of the present study was to investigate the effect of response bias (the sensory-independent factor) on resolution thresholds of Sloan letters in central and paracentral vision. MethodsNine subjects with normal ocular health were recruited for this study. Using the method of constant stimuli, individual Sloan letters resolution thresholds were measured at 0{degrees} (central) and at {+/-}3{degrees} eccentricity along the vertical meridian of the visual field. Response biases and letter similarities were computed using Luces choice model. ResultsResults showed that the differences in resolution thresholds of individual Sloan letters were significant at the central (F (9, 80) =5.02, p<.001), the upper ({chi}2 (9) = 50.38, p<.05) and the lower ({chi}2 (9) = 56.32, p<.05) visual field locations. Unlike letter similarity measures, response biases showed significant correlations to the differences in thresholds at the central (r = -0.83, p<.05), the upper (r = - 0.73, p<.05) and the lower (r = -0.70, p<.05) visual field locations. ConclusionsOur findings suggest that response biases have a significant effect on resolution of Sloan letters that could result in overestimating resolution acuity in central and paracentral visual field locations.