Peripheral Visual Acuity in Myopes and Emmetropes Using Sampling–Limited Optotypes

Abstract

Abstract: : Purpose: Recent psychophysical evidence shows that retinal stretching limits visual performance in the retinal periphery in myopes. This was investigated by measuring recognition and detection acuity using sinusoidal gratings. This suggests a reduction in the sampling density of the retinal ganglion cells in the peripheral retina. The purpose of our research was to investigate whether the suggested low sampling density of the peripheral retina of myopes can be investigated using targets whose performance is related to the density of the retinal ganglion cells in the periphery . Methods: A group of young myopes and emmetropes took part in the study. The optotypes used were single high–contrast tumbling E letters and single high–pass (vanishing) tumbling Es at low contrast. The tasks were to resolve the orientation of the high contrast and vanishing E’s. Measurements were carried out at three different eccentricities (fovea, 5° and 10°) in the central vertical meridian of the inferior visual field. The tested eccentricities and the orientations of the targets were randomised. Results:Results show that visual resolution was significantly lower at 5° and 10° with E letters and was poorer at 10° in the peripheral field with vanishing optotypes in myopes compared with emmetropes (Mann–Whitney U test: p < 0.05). <BR Conclusions: We hypothesised that if ocular elongation is accompanied by increased under–sampling of peripheral images in myopic eyes this should lead to lower visual acuity in the periphery of myopic eyes compared to emmetropic eyes using sampling–limited visual resolution tasks. Our results confirm this hypothesis and show that sampling–limited tests demonstrate differences in peripheral visual function between myopes and emmetropes at 5° and 10° retinal eccentricity.

Keywords: myopia • visual acuity • refraction