• A simple and informative method is described for determining the type and extent of color defects. The subjects' responses are registered automatically on a chromaticity diagram that is based on the newtonian model. Color defects are readily identifiable by a skewing of the normal central gray area toward the defectively perceived color. The examination permits independent variation of hue and saturation for each color and requires less than five minutes for the entire procedure. Unlike conventional color tests, the present method indicates exactly what colors are or are not seen at any level of saturation.
Gunkel RD, Cogan DG. Colorimetry by a New Principle. Arch Ophthalmol. 1978;96(2):331-334. doi:10.1001/archopht.1978.03910050193016