Therapeutic regimes for improving visual function in a subject having a deficiency in endogenously produced 11-cis retinal comprising administering the synthetic retinal derivative as a divided dose over 2-7 days then providing a resting period of 7-28 days after which the second dose of the synthetic retinal derivative is administered. Preferred synthetic retinal derivatives are 9-or 11-cis-retinyl esters. Disorders associated with deficiency in endogenously produced 11-cis retinal include retinitis pigmentosa and Leber congenital amaurosis
