NPR currently has an article and audio segment available about David Stewart, a man who lost his sight, and subsequently developed Charles Bonnet Syndrome:
Stewart has Charles Bonnet syndrome, a condition that often affects people with macular degeneration or diabetic eye disease. A surprisingly large percentage of people who lose sight start seeing things, says ophthalmologist Jonathan Trobe of the University of Michigan.
“The brain is doing a mash-up of stored visual memories,” says Trobe. When visual cells in the brain stop getting information — which happens when your rods and cones stop working — the cells compensate, he explains. If there’s no data coming in, they make up images. They hallucinate.
Readers of our anthology Darklore Volume 1 will recognise this syndrome – author/researcher Paul Devereux wrote about it at length in his essay “Visions of the Blind”.