achromatopsia a·chro·ma·top·si·a (ə-krō'mə-tŏp'sē-ə) or a·chro·ma·top·sy (ə-krō'mə-tŏp'sē)
n.
A severe congenital deficiency in color perception, often associated with nystagmus and reduced visual acuity. Also called achromatic vision, monochromatism.