Color mixture thresholds measured on a color television--a new method for analysis, classification and diagnosis of...

A color television display can be used to determine color and brightness discrimination thresholds using identical adaptation conditions and experimental technique. The color discrimination threshold is measured by using an equiluminous test spot--i.e. one which differs in color from the surrounding screen but has the same luminance. Because there is no brightness clue, the subject is forced to detect such a spot by using color discrimination. It is shown how color and brightness thresholds may be determined from threshold measurements of different color-mixtures even though it is not known beforehand which stimulus will be equiluminous for the subject. Results are shown for normal subjects, congenital color defectives and for two patients having optic nerve disease who show respectively non-selective and selective loss of color discrimination compared to brightness discrimination. Normal control data are presented, illustrating the effect of eccentricity, optical blur, viewing distance, pupil size and age. It is concluded that the technique is relatively insensitive to moderate variations in these factors and that it is more sensitive in detecting selective color loss than a spectral sensitivity technique which has been described previously.