Odd as it sounds, a surprisingly large number of people who lose their sight start seeing things.
Ophthalmologists call it Charles Bonnet Syndrome, a condition that often affects people with macular degeneration or diabetic eye disease.
David Stewart, a former executive with the Corporation for Public Broadcasting, first experienced it when he was listening to a book on tape about sailors crossing the Hudson River.
As Stewart, who is blind, mused about the sailors, one of them appeared in his head - not a dreamy fantasy, but a vivid, highly detailed, very real-like hallucination.
“He had on a cap, a blue cap with a polished black beak and he had a pipe in his mouth.” The sailor gazed right at Stewart. Then the sailor winked.
To learn more about Charles Bonnet Syndrome, Click here to listen to, or read, Robert Krulwich’s story on National Public Radio.