SWS-Cone Letter Identification in Central and Peripheral Vision

Abstract

Abstract: : Purpose: Recent studies have shown that the SWS-cone acuity is limited by the underlying ganglion cell density (sampling limited) in both fovea and periphery while achromatic acuity is sampling limited only in the periphery. Based on these findings we wanted to determine if identification of complex objects such as letters would differ in any respect under SWS-isolating and achromatic conditions between the fovea and the periphery. Methods: Single Sloan letters were presented in random order and size on a computer monitor (90% contrast) in the fovea and at 10 deg eccentricity under achromatic and SWS isolating conditions. Five different sizes were used to cover the range from 0% to 100% correct identification. Results: The identification of SWS-isolating letters at the locations tested was much poorer than that of achromatic letters The SWS letter acuity decreased from fovea (0.82 log MAR) to periphery (1.32 log MAR) but at a lower rate than the achromatic letter acuity (-0.14 log MAR to 0.52 log MAR). Although many factors could contribute to the poor SWS letter identification, the performance is generally consistent with the sampling limits of the ganglion cells with SWS-cone input, i.e. small bistratified cells. Conclusions:SWS-letters identification across the retina varies in accordance with the prediction based on sampling density of small bistratified cells.

Keywords: visual acuity • color vision • ganglion cells