Animal models in research on retinal degenerations: past progress and future hope.

The retinal degenerations (RDs) are a family of inherited retinal degenerative diseases (dystrophies) that lead to vision loss. Although phenotypically very different, the RDs have several characteristics in common. They all are caused by gene mutations or at least have a genetic component in the etiology. They all lead to photoreceptor dysfunction, many leading to the death of both rod and cone photoreceptors. The mechanism of cell death in most of the RDs seems to be through the process of apoptosis. It is estimated that more than fifteen million people around the world have vision loss due to an inherited RD. Many of these are patients with the dry form of age-related macular degeneration (AMD) who retain partial functional vision. However, some have other degenerative conditions such as retinitis pigmentosa, Leber congenital amaurosis or wet AMD and can suffer from severe vision loss or total blindness.