Inability to distinguish between some or (usually) all colours; absence, severe impairment, or loss of colour vision; colour blindness, especially monochromatism.
((n.) Color blindness; inability to distinguish colors;
Daltonism.)
Origin:
Mid 19th century; earliest use found in The Lancet. From German Achromatopsie, † Achromatopsia from ancient Greek ἀχρώματος + Hellenistic Greek -οψία.