VARIATIONS IN PHOTORECEPTOR DIRECTIONALITY ACROSS THE CENTRAL RETINA

Cones show a differential sensitivity to light coming from different p ortions of the pupil, typically being most sensitive to light from the center of the pupil. We measured the directional properties of the co nes across the central 6 deg of the retina, using an optical imaging t echnique. We find that the cones in the center of the fovea have the b roadest tuning. The width of the angular tuning changes rapidly ti-om 6 deg to 1 deg retinal eccentricity, with cones at 1 deg being much mo re narrowly tuned than the cones in the center of the fovea. Direction al tuning of the cones remains relatively constant from I deg to 3 deg retinal eccentricity. Receptoral disarray contributes minimally to th e measured directional properties of the foveal cones, and there is no evidence of asymmetry between horizontal and vertical retinal locatio ns. There are only small differences among the five subjects in the ch ange in angular tuning of the cones with retinal location. We find tha t at the foveal center the directional tuning of the cones is limited by the diameter of the cone apertures. (C) 1997 Optical Society of Ame rica.