Comparison of cone directionality determined by psychophysical and reflectometric techniques

We measured the directionality of the cones with both a psychophysical (Sti les-Crawford I) technique and an optical technique. The two sets of measure ments were made in the same subjects, with stimuli as similar as possible u sed. The two types of measurements gave similar estimates of the location i n the pupil toward which the cones were optimally aligned. However, the two measurements gave quite dissimilar estimates of the width of the direction al sensitivity. On average, optical measurements were half as broad as psyc hophysical measurements in the fovea, but there were substantial individual differences. At 2-deg retinal eccentricity the difference between techniqu es was even more marked. (C) 1999 Optical Society of America [S0740-3232(99 )01710-X].