L and M cone relative numerosity and red-green opponency from fovea to midperiphery in the human retina

The relative numerosity of the long-wavelength-sensitive (L) and middle-wav elength-sensitive (M) cones and the red-green color appearance, as assessed by means of unique yellow, are stable from fovea to midperiphery (+/-28 de g nasotemporal). As foveal tests decrease in size, unique yellow progressiv ely shifts toward longer wavelengths, favoring a model of red-green opponen cy carried by cells whose centers receive input from either L or M cones an d whose surrounds receive mixed contributions from both. Individual differe nces in unique yellow over a 20-nm range and the relative numerosity of L a nd M cones can be linked by means of this model, suggesting that the relati ve number of L and M cones is a factor that regulates individual variations in red-green color appearance. (C) 2000 Optical Society of America [S0740- 3232(00)00903-0].