Color vision in the peripheral retina. I. Spectral sensitivity.

Spectral sensitivity was measured by heterochromatic flicker photometry both in the fovea and at 45 degrees in the periphery, using a 1200 troland standard. At each location, sensitivity functions were obtained using both large and small targets. While the foveal functions were normal, the peripheral ones showed a large enhancement in sensitivity to short wavelengths relative to long wavelengths. Similar results in the past had been criticized on the ground that they might have been due to differential chromatic adaptation of cone mechanisms. In this study such an interpretation was ruled out by additional control experiments including varying luminance and wavelength of the standard light. The possibility of a rod contribution to the peripheral functions could not be eliminated although several different techniques, including the Stiles-Crawford effect, were used to try to isolate cone mechanisms.