GNAT2 and achromatopsia: Achromatopsia (ACHM; synonymous with rod monochromatism; ACHM2, MIM 216900; ACHM3, MIM 262300; ACHM4, MIM 613856; ACHM5/COD4, MIM 613093; ACHM6/RCD3A, MIM 610024; and ACHM7, IM616517) is a rare, autosomal recessive disorder with an estimated prevalence of 1 in 30,000 to 1:50,000.