Bi-allelic RPE65 mutations causing the severe inherited retinal dystrophy, Leber congenital amaurosis (LCA, termed LCA2) or autosomal recessive retinitis pigmentosa (arRP), a somewhat milder disease, albeit with early onset, were first described in the late 1990s [17,18,19,20] and are thought to account for about 7–16% of all LCA cases and 1–2% of those of arRP. Here, RPE65 is linked to Leber congenital amaurosis.