RDH8 and retinal degeneration: Mouse models of Stargardt’s disease: single gene knockouts: abca4-/- and particularly rdh8-/-, or double knockout abca4(-/-)rdh8(-/-) mice exhibit delayed clearance of all-trans-retinaldehyde after exposure to light and increased susceptibility to retinal degeneration manifesting itself as loss of photoreceptive neurons, which is accelerated when animals are raised in cyclic light as opposed to when rearing in the dark [2,64,82,83,84,85,86,87,88].