Retinal blindness is a degenerative condition in which the detectors in the retina (light, shape, colour) do not function. Retinal blindness comes in two main types - retinatis pigmentosa, a hereditary condition that can strike in youth and gradually causes the sufferer to lose their eyesight; and macular degeneration, which usually, but not always, strikes late in life. Age-related macular degeneration is one of the two main causes of legal blindness.
Retinal blindness afflicts roughly 1 million people in the USA - roughly one-third of all blind people.