Binocular summation of astigmatism with reference to monovision

Abstract

Binocular summation is the basic mechanism underlying the use of monovision correction. In this experiment we have investigated the effect of uncorrected astigmatism (1.00DC) on binocular visual acuity with and without monovision. Low levels of uncorrected astigmatism have only a small effect on binocular visual acuity under normal binocular viewing conditions. However under monovision conditions, low levels of uncorrected astigmatism have a significantly greater effect on binocular visual acuity. This presumably occurs because of the diminished opportunity for binocular summation under monovision conditions. To conduct this experiment we designed a new acuity chart (the Donut chart), based on circular targets, which provided a gap resolution task which was not orientation dependent.