Spectral sensitivity and wavelength discrimination of the human peripheral visual field

Spectral sensitivity and wavelength discrimination are determined along the nasal horizontal meridian of the human peripheral retina. The target size as a function of eccentricity is varied according to a particular cortical magnification factor. Spectral sensitivity is measured by flicker photometry parameterized for the flicker frequency (10-20 Hz) and is found to be independent of the eccentricity (0-80 degrees) for 20-Hz flicker photometry after correction of the foveal spectral sensitivity for macular pigment absorption. This 20-Hz function is chosen as being representative for the peripheral luminous-efficiency function and is used in the wavelength-discrimination experiments. The peripheral retina can perform wavelength discrimination up to an eccentricity of 80 degrees. If field-size scaling according to the eccentricity-dependent cone density, the cortical magnification factor, or the reciprocal of the interganglion cell distance is applied, then wavelength-discrimination performance from 8 degrees to 80 degrees eccentricity is roughly the same. Foveal wavelength discrimination is considerably better than peripheral wavelength discrimination.