RPE65 and Leber congenital amaurosis: LRAT encodes Lecithin:retinol acyl transferase, a key enzyme in the vitamin A recycling pathway (visual cycle), with LRAT deficiency associated with a similar phenotype to RPE65-deficiency, although being far less common.9 88 As described for RPE65-deficiency, the synthetic prodrug QLT091001, a precursor to 9-cis-retinal, has been shown in a phase I trial to improve VA and kinetic visual fields in LRAT-LCA, with a phase III trial anticipated in the future.