Retinoblastoma is a cancerous tumor of the retina, the thin nerve tissue lining the back of the eye which senses light and forms images. The disease occurs most commonly in younger children, usually before the age of five. About 300 children are diagnosed with retinoblastoma each year in the United States. The disease accounts for about 3 percent of childhood cancers.
Adults can develop retinoblastoma too, but it is extremely rare.
Retinoblastoma may be hereditary or nonhereditary. The hereditary form generally affects younger children and may occur in one or both eyes. A child who has tumors in both eyes almost always has the hereditary form of the disease. Retinoblastoma that occurs in only one eye usually is the nonhereditary form, which is more often found in older children. About 75 percent of cases occur in only one eye, and about 25 percent occur in both eyes.