Some studies have also provided estimates as a proportion of relevant IRD subgroups: the aforementioned Spanish study found GUCA1A variants accounted for 3% of families (n = 4) within the autosomal-dominant non-RP IRD subgroup (the fifth family was reported to have RP)11; a previous German study of 251 consecutive unrelated cases of macular dystrophy or cone/cone-rod dystrophy (of whom 185 had a positive genetic diagnosis found) reported 3 families with disease associated with GUCA1A, corresponding to a proportion of 1.2% (or 1.6% of cases with a positive molecular diagnosis).7 Here, GUCA1A is linked to cone-rod dystrophy.