Charles Bonnet Syndrome

Charles Bonnet syndrome is a condition, also described as visual release hallucinations, in which a person with significant vision loss, whether partial or severe, experiences vivid visual hallucinations even though their other mental faculties remain intact and they generally recognize, at least while their thinking stays clear, that what they are seeing is not real. The Swiss naturalist Charles Bonnet first described the condition in 1760, having observed it in his own nearly blind grandfather, though the syndrome was not formally named after him in English-language psychiatric literature until 1982. The leading explanation holds that severe visual impairment deprives the brain's visual processing regions of their normal sensory input, and that this sensory deprivation leads those regions to become disinhibited, generating spontaneous neural activity that the brain then experiences as visual content; brain imaging studies have linked the hallucinations to activity in the ventral occipital lobe. The hallucinations themselves range from simple patterns of shapes, lines or colors to fully detailed, complex scenes involving people, animals or landscapes, with faces and cartoon-like figures reported particularly often, and the condition affects a substantial share of older adults with major vision loss, with studies finding a prevalence of roughly ten to forty percent among people over sixty-five with significant visual impairment, though the true rate is likely undercounted because a majority of affected people hesitate to tell their doctors about the hallucinations for fear of being thought mentally ill.