RPE65 and Leber congenital amaurosis: Visual cycle modulators have been under development for the last 10 years, with the aim of either decreasing the accumulation of various retinoid derivatives or to supply deficient compounds.62 In RPE65-related and LRAT (OMIM 604863)-related LCA/EOSRD, all-trans-retinal does not get converted back to 11-cis-retinal, interfering with the visual cycle, and ultimately leading to retinal degeneration and visual loss.63 It has been suggested that exogenous supply of 11-cis-retinal may prevent (or slow) photoreceptor degeneration.