Abstract
Purpose. New corrective techniques (“monovision”) for presbyopia correct one eye for near vision and the other for distance vision, creating two different focal distances. Our aim is to investigate relative dominance between a sharp (S) image in one eye and a blurred (B) version of S in the companion eye, mimicking monovision. Casual long observations ([[gt]]8s) under steady fixation reveal that B's dominance increases as eccentricity increases.
Methods. We tested possible binocular rivalry as a function of eccentricity E using two paradigms: (1) We rendered the grey-level images S and B in red-black and green-black (counterbalancing color and spatial frequency content across trials). Observers reported the color of a circular patch at various eccentricities. This effectively indicated the relative dominance of S and B because of the correlation of color and spatial frequency content in the stimuli. (2) Using grey-level images for both eyes, observers detected a probe presented with equal probability to either S or B at various eccentricities. Their performance indicated the relative dominance of S and B, because probes are harder to detect on suppressed images and thresholds increase.
Results. As a rule, S dominated B almost exclusively in the fovea ([[gt]]80%). Paradigm (1): As E increased, the probability of reporting the color of B increased. Paradigm (2): As E increased, it became significantly more difficult to detect the probe on the S image, whereas detectability did not change significantly with E for the B image.
Conclusions. The results in both paradigms are consistent with the following pattern of dominance: The dominance of S and B decreases and increases, respectively, with increasing E. We normally have the illusion of a sharp focused image throughout the visual field. S/B binocular stimulation is a rare case where we are made aware of the low-frequency dominance in the periphery.