Charles Bonnet syndrome

Overview
Charles Bonnet syndrome (CBS) is named after the Swiss naturalist Charles Bonnet. In 1760 he described a condition in which vivid, complex visual hallucinations (fictive visual percepts) occur in mentally healthy people. One characteristic of these hallucinations is that they usually are "lilliput hallucinations" (hallucinations in which the characters or objects are smaller than in reality). He first documented it in his 87-year-old grandfather, who was nearly blind from cataracts in both eyes but perceived men, women, birds, carriages, buildings, tapestries, and scaffolding patterns.

Most who are affected by this are people with visual impairments due to old age, damage to the eyes or optic pathways. In particular, central vision loss due to a condition such as macular degeneration combined with peripheral vision loss from glaucoma may predispose to CBS, although most people with such deficits do not develop the syndrome.

This syndrome is well portrayed in Vilayanur S. Ramachandran's book Phantoms in the brain.