Retinol dehydrogenase 8 is an enzyme that in humans is encoded by the RDH8 gene.

All-trans-retinol dehydrogenase (RDH8) is a visual cycle enzyme that reduces all-trans-retinal to all-trans-retinol in the presence of NADPH (Rattner et al., 2000 [PubMed 10753906]). It is a member of the short chain dehydrogenase/reductase family and is located in the outer segments of photoreceptors; hence it is also known as photoreceptor retinol dehydrogenase. It is important in the visual cycle by beginning the rhodopsin regeneration pathway by reducing all-trans-retinal, the product of bleached and hydrolysed rhodopsin (Rando, 2001 [PubMed 11710234]). This is a rate-limiting step in the visual cycle (Saari et al., 1998 [PubMed 9667000]).[supplied by OMIM, Mar 2008].
Function: Retinol dehydrogenase with a clear preference for NADP. Converts all-trans-retinal to all-trans-retinol. May play a role in the regeneration of visual pigment at high light intensity (By similarity).