Visual Hallucinations and The Charles Bonnet Syndrome
Visual release hallucinations, also known as Charles Bonnet syndrome or CBS, are a type of psychophysical visual disturbance in which a person with partial or severe blindness experiences visual hallucinations.
First described by Charles Bonnet in 1760, The term Charles Bonnet syndrome was first introduced into English-speaking psychiatry in 1982. A related type of hallucination that also occurs with a lack of visual input is closed-eye hallucination.
People with significant vision loss may have vivid recurrent visual hallucinations (fictive visual percepts). One characteristic of these hallucinations is that they usually are "lilliputian" (hallucinations in which the characters or objects are smaller than normal). Depending on the content, visual hallucinations can be classified as either simple or complex. Simple visual hallucinations are commonly characterized by shapes, photopsia, and grid-like patterns. Complex visual hallucinations consist of highly detailed representations of people and objects. The most common hallucination is of faces or cartoons. Sufferers understand that the hallucinations are not real, and hallucinations are only visual, that is, they do not occur in any other senses (such as hearing, smell, or taste).
Even though people of all ages may be afflicted by Charles Bonnet syndrome, those within the age range of 70 to 80 are primarily affected. Among older adults (> 65 years) with significant vision loss, the prevalence of Charles Bonnet syndrome has been reported to be between 10% and 40%; a 2008 Australian study found the prevalence to be 17.5%. Two Asian studies, however, report a much lower prevalence. The high incidence of underreporting this disorder is the greatest hindrance to determining the exact prevalence. Underreporting is thought to be a result of sufferers being afraid to discuss the symptoms out of fear that they will be labeled with unsound minds.
