Retinal pigmentation, visual acuity and brightness levels.

This study investigates the hypothesis that the degree of retinal pigmentation in the human eye is adaptive as it relates to the maintenance of visual acuity in optically stressful environments, deserts and snowfields. Eighty-four subjects were examined, an estimation of their degree of retinal pigmentation made by ophthalmoscopic examination and their binocular visual acuity tested over ten levels of brightness. The general level of retinal pigmentation did not influence mean visual acuity within the levels of brightness used in this study. The hypothesis was, therefore, rejected, but with the proviso that this study should be extended to even higher levels of brightness than were obtained here. There was no difference in mean pupil size at various levels of illumination between individuals grouped by degree of retinal pigmentation.