Progress toward effective treatments for human photoreceptor degenerations.

Mutations in several dozen genes have been shown to cause inherited photoreceptor degeneration in humans and it is likely that mutations in several dozen more will eventually be identified. Careful study of these genes has provided insight into the cellular and molecular mechanisms of human photoreceptor disease and has accelerated the development of a number of different classes of therapy including: nutritional supplementation, toxin avoidance, small-molecule drugs, large-molecule drugs, gene replacement, cell replacement, and even retinal prostheses. The retina is a very favorable system for the development of novel treatments for neurodegenerative disease because of its optical and physical accessibility as well as its highly ordered structure. With several forms of treatment for inherited retinal disease in or near clinical trial, one of the greatest remaining challenges is to educate clinicians in the appropriate use of genetic testing for identifying the individuals who will be most likely to benefit from each specific modality.