Visual resolution in the periphery

Visual acuity thresholds were determined for two Os with a 3-deg square grating target presented for 0.2 sec within a steadily illuminated surround field matched in luminance to the test field. Measurements were made in the fovea, and at 10, 20, and 30 deg along the horizontal meridian of the temporal retina, at luminances between ?3.5 and 3.0 log mL. The foveal acuity-luminance functions showed a large increase in acuity up to 1 or 2 log mL, but at peripheral locations very little increase occurred above 0 log mL. The maximum acuity reached at photopic luminances dropped sharply with increasing eccentricity. Visual acuities were two to four times higher than those previously reported for the periphery; methodological and target differences are presented to account for this result.