Enhancement of resolution acuity in a half-binocular viewing condition.

PURPOSE To investigate the effect of interocular stimulus similarity on foveal resolution acuity. METHODS Liquid crystal shutter goggles synchronized with the monitor refresh rate were used to present a Landolt C and surround bars to one or both eyes, in four viewing conditions (monocular, dichoptic, half-binocular, and binocular). Resolution acuity was measured in each condition in 22 normally sighted adults. RESULTS Resolution acuity was significantly better in the binocular condition than in the other three viewing conditions (binocular summation) and was significantly better in the half-binocular condition (with target presented to the test eye and bars presented to both eyes) than in the dichoptic condition (target presented to the test eye and bars presented to the nontested eye only). CONCLUSIONS Monocular resolution acuity depends in part on interocular similarities of the stimulus surrounding the central target. This finding may have implications in the design of stimuli for vision-training therapies.