Microspectrophotometric demonstration of four classes of photoreceptor in an old world primate, Macaca fascicularis.

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Abstract
Microspectrophotometric measurements reveal 4 classes of photoreceptor in the retina of the cynomolgus monkey, M. fascicularis, which possesses color vision similar to that of a normal human trichromat. Although the eyes were removed in bright illumination, the densities of pigment were comparable to those measured in dark-adapted rhesus retina. The mean wave-lengths of peak sensitivity (.lambda.max) for the 4 classes of photoreceptor were 415, 500, 535 and 567 nm. The band widths of the absorbance spectra decreased linearly as the wave-number of peak sensitivity decreased. Given a reasonable value for the axial density of the rod outer segment and correcting for lens absorption, a spectral sensitivity for human vision reconstructed from the P500 pigment would be systematically broader than the CIE [International Commission of Illumination] scotopic sensitivity function. From the P535 and P567 pigments it is possible to reconstruct human psychophysical sensitivities resembling the .pi.4 and .pi.5 mechanisms of W.S. Stiles. Although the P415 pigment has a .lambda.max much shorter than the psychophysically measured blue mechanisms, the 2 spectral-sensitivity functions are brought into proximity when the microspectrophotometric data are corrected for absorption by the optic media.