achromatopsia, achromatopsy

This is the compete form of a., characterized by severe deficiency of color perception, associated with nystagmus, photophobia, reduced visual acuity, and “day blindness”; autosomal recessive inheritance, caused by mutation in the cone photoreceptor cGMP-gated cation channel, alpha-subunit 3 gene (CNGA3) on chromosome 2q. SYN: achromatic vision, monochromasia, monochromasy, monochromatism (2). [G. a- priv. + chroma, color, + opsis, vision]

- atypical a. incomplete a. with normal visual acuity and no nystagmus. Cf.:dyschromatopsia.

- complete a. a. with absent color vision, nystagmus, reduced visual acuity, and light aversion. SYN: rod monochromatism, typical a..

- incomplete a. [MIM*200930] impaired but not absent color vision with less severely reduced visual acuity than in complete a., associated with photophobia and nystagmus; autosomal recessive inheritance. An autosomal dominant [MIM*180020] form and several X-linked [MIM*304020, MIM*300085, and MIM*303700] forms exist.

- typical a. SYN: complete a..