Retinitis pigmentosa is the name given to a group of diseases that affect the retina.

The retina, located in the back of the eye, acts like the film in a camera. It is a delicate layer of cells which picks up the picture and transmits it to the brain - where the "seeing" actually occurs.

In retinitis pigmentosa, the retina begins to degenerate, which first causes peripheral (side) vision and night vision to diminish, and then, usually only decades later, the central vision as well.

There are...