Abstract

There is evidence suggesting that the spectral positioning of cone photopigments varies among individuals with normal color vision. To examine this we obtained Rayleigh matches from 200 young (mean age = 20.6 yrs) color-normal individuals using large field substitution, a method which enhances color discrimination. The results reveal a discrete variation in color matches between individuals and a striking difference between males and females. The color matches made by males fall into two distributions nearly equal in size. The color matches of the females are trimodally distributed: two modes correspond to the male matches, but a majority of females match in a position intermediate to the male modes. The modal nature of the distributions indicates a stepwise variation in the spectral positioning of the cone mechanisms while the male bimodality indicates that among normals only one cone mechanism varies. The distribution of matches made by females can be accounted for by assuming that this polymorphism is X-chromosome linked. Analysis of the color matches reveals that (a) it is the long-wavelength cone mechanism that varies among normal humans and (b) the difference in λ_max between the two types of long-wavelength mechanisms is ~3 nm. These results may provide insights into the mechanisms that produce inherited color vision defects.

© 1985 Optical Society of America