Retinitis Pigmentosa (RP) is the name given to a group of hereditary diseases of the retina of the eye. The retina is located at the back of the eye and acts like film in a camera, receiving and processing all of the pictures that come into view. The retina is a delicate layer of cells that pick up the pictures and deliver them to the brain. In the human retina there are two types of light sensitive cells-rods and cones. Cone cells are located in the center of the retina, the Macula, and are used to see color and precise objects like small print. Rod cells are much more numerous and are necessary for peripheral and night vision. There are about 120 million rods in the human eye, mostly at the outer edge of the retina. In a person with RP, a breakdown has occurred in the function of the rods.
Since the retina is so complex, there are many forms of RP, and as a result, many different symptoms. But the basic deficiencies in all people with RP are a loss of peripheral vision, often called “tunnel vision”, and poor night vision, often referred to as “night blindness”. RP is a degenerative disease, which means that rod cells will continue to dysfunction over time, causing the further loss of peripheral vision but eventually entering the central vision, leading to total blindness. This happens at various times depending on the person, sometimes occurring in young children but many times not until middle-age or beyond. Some people may be diagnosed with RP as a child if their vision difficulties are apparent, and others may not be diagnosed until a much later age.