Refinement of Checkerboard Targets for Measurement of Visual Acuity Limens

Abstract

Checkerboard targets to be used in the precise measurement of visual acuity have been validated with the aid of a chi-square statistic.Secondary cues which lead to spurious data have been eliminated in some targets by using a black border, and accurate acuity measurements were obtained. For the conditions under which we worked we estabblished the interchangeability of varying visual angle in small ranges (a) by changing target size and (b) by changing target distance. The range of stimuli required to establish an acuity limen is approximately 12 sec of visual angle.