color vision deficiency, color-blindness

color vision deficiency, color-blindness (In French défaut de vision des couleurs, achromasie) deviation from normal color vision (accurate color daytime vision) among approx. 5% of human beings on account of the differing functioning (anomaly: color pair metamerism) or of the failure (anopia: color pair confusion) of one (dichromatopsia) or two (monochromasy) of the three types of retinal cones. Persons with color vision deficiency are unfit for occupations in which colors play an important role; the required determination of normal vision is effected using the Stilling-Hertel test, and of the type of color vision deficiency with Ishihara plates.