CNGA3 and achromatopsia: Variants in 6 genes are implicated in achromatopsia, which together likely explain more than 90% of cases.5,6 Most prevalent are pathogenic variants in the 2 genes that encode the α and β subunits of the cone cyclic nucleotide-gated (CNG) channel, CNGA3 (found in approximately 25%-28% of European and US cases) and CNGB3 (50% of cases).7 CNG channels are essential components of the phototransduction process in cone photoreceptors, which enable daylight vision, high spatial and temporal resolution, color discrimination, and stable fixation.