Physiology of Normal and Abnormal Colour Vision

Abstract

The physiology of colour vision is reviewed in the light of recent neurophysiological and anatomical studies in vertebrate retinas. The physiological correlate of trichromasy is the existence of three classes of cone cells, each possessing exclusively one of three photopigments with maximum spectral sensitivity at either 440 nm, 540 nm or 570 nm. The electrical responses of single cells of the various types within the retina and lateral geniculate nucleus exhibit both spatial and chromatic coding which is opponent in character. The horizontal and amacrine cells show sophisticated responses which demonstrate their important roles in the processing of information about colour vision. Human abnormal colour vision is reviewed in the light of recent psychophysical studies. Red-green dichromasy is due to the absence of one of the two photopigments normally active in the red-green range of the spectrum. In the red-green anomalous trichromasies one of the photopigments active in that range is replaced by an abnormal photopigment although the spectral loci of the peak sensitivity of these photopigments and the shape of their absorption curves have not yet been accurately identified. The traditional association of mono-chromasy with a rod-only retina has been challenged by the finding of cone cells in histological preparation of eyes of achromats, and the psychophysical evidence that more than one receptor type participates in visual function. One of these receptor types is the normal rod but the other may be a normal blue-sensitive cone or a cone filled with rhodopsin, the rod photopigment. Language: en