Interocular difference in Rayleigh matches of color normals

The Rayleigh match typically is used to assess whether an individual has normal or red/green-defective color vision. There is substantial variation, however, in the Rayleigh matches of color-normal observers, and even differences in the matches from the left eye and right eye of a single observer. We confirmed this interocular difference in two independent samples of normals, and measured additional color matches to seek the cause of the difference. Color matches that varied the wavelength in the mixture field or the field size (i) fail to provide any evidence of an interocular difference in the wavelength of peak sensitivity of photopigment (Xmax) and (ii) suggest the difference often is due to effective optical density of photopigment. We conclude that an interocular difference in Rayleigh-match midpoint (but not range) is common, and due to effective optical density and/or pre-receptoral spectrally selective filtering.