Large-field trichromacy in protanopes and deuteranopes.

Protanopes and deuteranopes do not accept the classical dichromatic matches when field size extends to 8 degrees visual angle. Their unique matches of spectral yellow to a mixture of red and green are then mediated by the photoreceptors of small-field dichromacy interacting with a photoreceptor with the spectral sensitivity of rhodopsin. Our data suggest that large-field trichromacy is a general feature of protanopia and deuteranopia.