Interestingly, these data which support a common mechanism of photoreceptor degeneration in rd3 and GC double knock-out mice [43] are consistent with the phenotypic overlap between LCA12 and LCA1. Indeed, the review of the natural history and clinical data of our patients and that of the two original RD3 families [21], [35] delineate a homogeneous phenotype unambiguously consistent with the diagnosis of congenital and dramatically severe cone-rod dystrophy (LCA type I) originally described in LCA1 patients harboring GUGY2D mutations [3]. This evidence concerns the gene GUCY2D and Rod-cone dystrophy.