Charles Bonnet Syndrome
Described by the Swiss naturalist and philosopher Charles Bonnet in 1760, this syndrome consists of well-formed (complex), elaborate and often stereotyped visual hallucinations, of variable frequency and duration, in a partially sighted (usually elderly) individual who has insight into their unreality. Hallucinations may disappear on eye closure. Predisposing visual disorders include cataract, macular degeneration, and glaucoma. There are no other features of psychosis or neurological disease, such as dementia. The pathogenesis of the visual hallucinations is uncertain. Reduced stimulation of the visual system leading to increased cortical hyperexcitability is one possible explanation (the deafferentation hypothesis), although the syndrome may occasionally occur in people with normal vision. Treatment consists primarily of reassurance. Pharmacological treatment with atypical antipsychotics or anticonvulsants may be tried but there is no secure evidence base.
Jacob A, Prasad S, Boggild M, Chandratre S. Charles Bonnet syndrome – elderly people and visual hallucinations. BMJ 2004; 328: 1552-1554
Menon GJ, Rahman I, Menon SJ, Dutton GN. Complex visual hallucinations in the visually impaired: the Charles Bonnet syndrome. Survey of Ophthalmology 2003; 48: 58-72