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Charles Bonnet syndrome (CBS) is a disease in which visual hallucinations occur as a result of vision loss. CBS is not thought to be related to psychosis or dementia and people with CBS are aware that their hallucinations are not real. The hallucinations people with CBS experience can be described as simple or complex. Simple hallucinations include shapes and patterns, while complex include images of people, vehicles, animals, and plants. Hallucination episodes can range from a few seconds to hours and may recur over the course of several days to years. The cause of CBS is not well understood, but it is thought to be related to the brain continuing to interpret images, even in their absence. There are many underlying diseases of vision loss that are associated with CBS, such as macular degeneration and stroke. Hallucinations may resolve in instances where the the underlying vision issue can be corrected (such as with cataracts).