What Associates Charles Bonnet Syndrome with Age-Related Macular Degeneration?

Charles Bonnet syndrome (CBS) is a condition related to patients with visual loss due to age related macular degeneration or glaucoma that are having complex visual hallucinations. The CBS was first described by Swiss physician Charles Bonnet in 1760. Affected patients, who are otherwise mentally healthy people with significant visual loss, have vivid, complex recurrent visual hallucinations (VHs). One characteristic of these hallucinations is that they usually are "Lilliputian hallucinations" as patients experience micropsia (hallucinations in which the characters or objects are distorted and much smaller than normal). The prevalence of Charles Bonnet Syndrome has been reported to be between 10% and 40%; a recent Australian study has found the prevalence to be 17.5%. The high incidence of non-reported CBS is thought to be as a result of patient's fear to report the symptoms as they could be labeled as mentally insane since those type of visual hallucinations could be found in variety of psychiatric and neurological disorders such as drug or alcohol abuse (delirium tremens), Alice in Wonderland syndrome (AIWS), psychosis, schizophrenia, dementia, narcolepsy, epilepsy, Parkinson disease, brain tumors, migraine, as well as, in long term sleep deprivation. VHs can also be presented as the initial sign of the Epstein-Barr virus infection in infectious mononucleosis. Patients who suffer from CBS usually possess insight into the unreality of their visual experiences, which are commonly pleasant but may sometimes cause distress. The hallucinations consist of well-defined, organized, and clear images over which the subject has little control. It is believed that they represent release phenomena due to deafferentiation of the visual association areas of the cerebral cortex, leading to a form of phantom vision. Cognitive defects, social isolation, and sensory deprivation have also been implicated in the etiology of this condition. This study was conducted on 350 patients diagnosed with Age-Related Macular Degeneration (AMD) and shows incidence of CBS in 13% of patients with AMD. Furthermore, we have found higher incidence of CBS in patients with massive loss of vision in peripheral visual field which is not age related.