Charles Bonnet Syndrome Hallucinations more Common than was Thought


Vivid hallucinations in Charles Bonnet Syndrome last much longer and have more serious consequences than formerly believed, researchers from King’s College London have found.

The study, involving 492 visually impaired people who had experienced visual hallucinations, show there is a serious divergence between medical opinion and the condition’s actualities.

Charles Bonnet Syndrome is generally thought by medical professionals to be relatively benign and short-lived. But, the new study demonstrates that 80% of respondents had hallucinations for five years or more and 32% found them mostly unpleasant, distressing and negative.

What is Charles Bonnet syndrome?

Charles Bonnet syndrome is the experience of complex visual hallucinations in a partially or severely sighted person. Patients are mentally healthy but often have considerable visual impairment. They experience vivid and complex recurrent visual hallucinations, and the most common hallucination is of faces or cartoons. Sufferers do understand that the hallucinations are not real,

The disease is named for the Swiss naturalist Charles Bonnet, who documented the condition in 1760. He first saw it in his 89-year-old grandfather who was nearly blind from cataracts in both eyes but saw men, women, birds, carriages, buildings, tapestries, physically impossible circumstances and scaffolding patterns.

The study described people as having “negative outcome Charles Bonnet Syndrome” because the group was more likely to have recurrent, fear inducing, longer duration hallucinations, which affected everyday activities. They were more likely to think hallucinations were due to serious mental illness, and less likely to have been warned about the possibility of hallucinations before they started.

Startling, Terrifying and Frightening

38% of the subjects said their hallucinations were startling, terrifying or frightening when they first occurred. 46% said the hallucinations had an effect on their ability to complete daily tasks. 36% of people who discussed the issue with a medical professional said the professional was “unsure or did not know” about the diagnosis.

“Charles Bonnet Syndrome has been traditionally thought of as benign”, said lead researcher Dr Dominic ffytche. “Indeed, it has been questioned whether it should even be considered a medical condition given it does not cause problems and goes away by itself. The results of our survey paint a very different picture. With no specific treatments for Charles Bonnet Syndrome, the survey highlights the importance of raising awareness to reduce the distress it causes, particularly before symptoms start. All people with Charles Bonnet Syndrome are relieved or reassured to find out about the cause of their hallucinations and our evidence shows the knowledge may help reduce negative outcome."

Those with macular disease are especially prone to Charles Bonnet hallucinations. Neurologists believe the hallucinations are a reaction of the brain to the loss of visual stimulation. More than half of people with severe sight loss experience them but many do not tell others for fear they will be thought to have a serious mental illness.

Age-related macular degeneration affects the central vision. It is the most common cause of sight loss in the UK, and more people will become affected as the population ages. Around half will have hallucinations at some stage.

“It is essential that people affected by sight loss are given information about Charles Bonnet Syndrome at diagnosis or as soon after as possible”, said Tony Rucinski of the Macular Society. “Losing your sight is bad enough without the fear that you have something like dementia as well. We need medical professionals to recognise the seriousness of Charles Bonnet Syndrome and ensure that people don’t suffer unnecessarily. More research is also needed to investigate Charles Bonnet Syndrome and possible ways of reducing its impact."


Thomas M Cox & Dominic H ffytche
Negative Outcome Charles Bonnet Syndrome
British Journal of Ophthalmology doi:10.1136/bjophthalmol-2014-304920

Last Updated on October 31, 2022