"Neurologist and author Oliver Sacks brings our attention to Charles Bonnett syndrome -- when visually impaired people experience lucid hallucinations. He describes the experiences of his patients in heartwarming detail and walks us through the biology of this under-reported phenomenon."
From Wikipedia: "Sufferers, who are mentally healthy people with often significant visual loss, have vivid, complex recurrent visual hallucinations (fictive visual percepts). One characteristic of these hallucinations is that they usually are "lilliput hallucinations" (hallucinations in which the characters or objects are smaller than normal).
Sufferers understand that the hallucinations are not real and the hallucinations are only visual, that is, they do not occur in any other senses, eg: hearing, smell or taste.
The prevalence of Charles Bonnet Syndrome has been reported to be between 10% and 40%; a recent Australian study has found the prevalence to be 17.5%. Two Asian studies, however, report a much lower prevalence.
The high incidence of non-reporting of this disorder is the greatest hindrance to determining the exact prevalence; non-reporting is thought to be as a result of sufferers being afraid to discuss the symptoms out of fear that they will be labelled insane.
Other symptoms include sufferers, who are predominantly female, complaining of electrical sensations in their perineum.
People suffering from CBS may experience a wide variety of hallucinations. Images of complex coloured patterns and images of people are most common, followed by animals, plants or trees and inanimate objects. The hallucinations also often fit into the person's surroundings."