Visual release hallucinations, also known as Charles Bonnet syndrome (CBS), refers to symptoms of visual hallucinations that occur due to vision loss from any underlying cause. The underlying condition may affect the eye, optic nerve, or the brain. Examples of underlying causes include macular degeneration, glaucoma, diabetic retinopathy, optic neuritis, surgery, and stroke.
CBS is thought to occur due to the interruption or destruction of the afferent connections of nerve cells in the visual system leading to disinhibition of the visual cortex. The subsequent spontaneous firing of neurons causes hallucinations.
Patients with CBS have insight into the unreal nature of their hallucinations. It is not a symptom of psychiatric illness or any other cause of dementia. CBS can occur in all age groups, but is more common in elderly patients. Patients may experience simple hallucinations, such as flashes of light or shapes, or they can be complex hallucinations, such as images of people, animals, landscapes, or cartoons. The hallucinations are commonly pleasant, but may cause anxiety. The duration of the hallucinations generally depends on the underlying cause. In some cases they may only last days to weeks, while in other cases the hallucinations may persist over several years.
The diagnosis of CBS is made in patients with vision loss in the absence of psychiatric disorders or other causes of hallucinations.
CBS is managed by treating the underlying condition causing the visual deficit, and providing reassurance to patients of their sanity. In some cases anticonvulsant or antipsychotic therapy may provide relief from CBS.