Subjects present at birth or early infancy with nystagmus, reduced visual acuity, photoaversion, and reduced or absent color vision.1,2 Disease-causing sequence variants in the genes encoding the alpha and beta subunits of the cone-specific cyclic nucleotide gated ion channel (CNGA3 and CNGB3, respectively) account for approximately 70% of all cases of ACHM,3 although variants in genes encoding for other components of the cone phototransduction pathway (GNAT2, PDE6H, PDE6C)4, –6 have also been associated with ACHM. This evidence concerns the gene CNGB3 and achromatopsia.