[Complex visual hallucinations in the visually impaired, the Charles Bonnet syndrome]

Charles Bonnet syndrome (CBS) is characterised by recurrent, complex and vivid visual hallucinations in the absence of cognitive dysfunction. Individuals with CBS usually maintain insight into the unreal nature of their hallucinatory experiences. There is a strong association between CBS and acquired visual loss and the most commonly described ocular pathology is age-related macular degeneration. However, CBS has been described in the context of visual impairment due to pathologies anywhere along the visual pathway. It is widely agreed that CBS is an underreported diagnosis caused by patients' reluctance to admit their hallucinatory experience because of fear of being labelled mentally ill. CBS is a diagnosis of exclusion and careful assessment must be made to ensure that other etiologies causing the symptoms are ruled out. Knowledge of CBS is nonetheless important, as it constitutes a benign differential diagnosis to diseases presenting themselves with visual hallucinations. In many patients the hallucinations generate considerable anxiety aggravated by the lack of awareness of CBS. Thus, a major part of the treatment is careful information about the benign nature of the condition. Optimizing visual function also has beneficial effects on the hallucinations. This is conducted by optical means such as visual aids and the employment of different types of surgical procedures.