S-cone spatial contrast sensitivity can be independent of pre-receptoral factors

Short-wavelength-sensitive (S-) cone-mediated thresholds have been used to study the early stages of visual loss, but due to the effects of non-neural factors (pupil size, lenticular density, macular pigment density) S-cone thresholds are often of limited clinical utility. The current study evaluates four possible effects of non-neural factors on S-cone contrast sensitivity, and shows how these can be minimized by measuring sensitivity for 1-5 c/deg with a range of retinal illuminances for blue test gratings on yellow backgrounds. The data are fit well with a simple four-parameter model which indicates that S-cone contrast sensitivity can be relatively independent on non-neural factors. A simple control experiment is described for evaluating the independence in individual patients.