Abstract
The retinal directional sensitivity, known as the Stiles-Crawford effect, is currently understood to originate in the retinal photoreceptors and to be due (at least in part, if not entirely) to the fact that individual receptors exhibit waveguide properties. The retina as a whole may be compared to a complex fibre optics bundle. In this study, the Stiles-Crawford effect in dichromatic observers was measured using (1) heterochromatic and (2) homochromatic bipartite photometric procedures at both low and high (bleaching level) luminances. The density of the photopigment and the wavelength dependence of the Stiles-Crawford effect in receptors containing a given photopigment were examined.