The effect of rods on perceptive field sizes at 10 degrees eccentricity in the four retinal quadrants

Abstract

Rod contributions to perceptive field sizes were measured for three observers at 10 degrees eccentricity in the four retinal quadrants using the “4+1” color scaling method. In the no-bleach condition, observers dark adapted for 30 min and then assigned hue percentages to the chromatic stimuli. In the bleach condition, observers dark adapted for 10 min, viewed a 20 deg, 7.32 log scot td bleaching field for 10 sec (bleaching 99.8% of the rod photopigment), dark adapted for an additional 4.5 min, and then assigned hue percentages to the stimuli during the cone plateau. Test stimuli were presented at 20 td for 500 msec with an 18 sec ISI and ranged from 440–660 nm in 10 nm steps. A series of test sizes were used in each retinal quadrant in order to calculate perceptive field sizes. Data were then fit by Michaelis-Menten growth functions. Measurements made in the four quadrants demonstrate that perceptive field sizes vary for the four elemental hues (red, green, yellow, blue) and are smaller in the bleach condition than in the no-bleach condition. These results indicate that rod signals increase perceptive field sizes.