Retinitis Pigmentosa or RP is a group of hereditary eye conditions that affect the retina. In RP, sight loss is gradual but progressive although it is unusual for people with RP to become totally blind.
The retina is light sensitive tissue at the back of the inside of the eye. It is made up of cells called rods and cones. Cones allow us to see fine detail and colour. Rods allow us to see when light is dim and peripheral vision beyond the main line of sight. RP causes the retina to its ability to respond to light.
Link to Retinitis Pigmentosa site www.brps.org.uk