Disease model: photoreceptor degenerations.

Retinal diseases can be caused by genetic or non-genetic factors, and typically involve specific cell layers within the retina. A large number of simple Mendelian gene defects are known to affect the photoreceptor cell layer. As photoreceptor cells cannot be maintained in vitro, the study of animal models is instrumental in understanding the disease process and in testing therapeutic approaches. This review briefly summarizes those animal models of photoreceptor diseases with defined genotypes.