RP can be diagnosed in a routine eye exam. It is usually diagnosed in young adulthood, although some forms of RP are evident in early childhood and other forms may not appear until later in life. Generally it is most difficult to diagnose in early stages. While gradual degeneration is the common feature of almost all forms of RP, there is not a predictable course for the degeneration, even for people in the same family. The progression is usually quite slow.
Vision sometimes appears to remain stable between annual eye examinations.
Some people with RP, as they grow older, do lose all their sight. A majority of people with RP are legally blind by the age of 40. To date, science has not been able to stop the degeneration of the retina or to restore lost vision. Carefully controlled doses of Vitamin A, for example, has shown promise in slowing the annual decline of remaining retinal function in people taking the supplement. Other measures currently being studied include retinal cell transplantation.