A Psychophysical Technique for Testing Explanations of Sensitivity Loss Due to Retinal Disease

Abstract

Although a retinal disease may affect a patient’s ability to differentiate colors and discriminate details, perhaps the most fundamental change is a loss of sensitivity to light. There are many explanations for a disease-related sensitivity loss. For example, a major component of this loss is often attributed to a decrease in quantum catching ability of the photoreceptors. A loss of photopigment, a misalignment of the photoreceptors, or a clouding of the lens or vitreous all decrease the number of quanta caught by the photoreceptors. In this paper, we show how an explanation, like the one above, can be tested using a psychophysical technique. In addition, we reject this particular explanation for the early loss of foveal sensitivity due to retinitis pigmentosa (RP) and suggest instead, that in this disease, and in several other retinal diseases we have studied, sensitivity loss is caused by a decreased responsiveness of individual retinal elements.