Article continues below ADVERTISEMENT The comedian lost his sight at age 22 due to a hereditary condition called retinitis pigmentosa. Retinitis pigmentosa (RP) is a group of rare eye diseases ...

One form, retinitis pigmentosa, belongs to a group of eye conditions that affects around 1 in 4,000 people in the United States and 1 in 5,000 people worldwide. This form of retinitis is typically ...