Heterochromatic flicker photometry (HFP) was employed to estimate how the h
uman long-wave sensitive (L) to middle-wave sensitive (Mj cone ratio varies
with retinal location in five color-normal males. Measurements were made a
t 0 degrees, 25 degrees, and 40 degrees in the temporal retina. The HFP spe
ctral sensitivities were fitted with a linear combination of L and M cone s
ensitivity functions derived from the Stockman and Sharpe(1) cone fundament
als, according to genotype. For the white (6500 K, 3 log Td) adapting field
conditions, the deduced UM cone ratios of each subject were nearly constan
t at all measured eccentricities, with individual values ranging from 0.9:1
to 3.4:1. (C) 2000 John Wiley & Sons, Inc.