Vivid hallucinations experienced by people with sight loss last far longer and have more serious consequences than previously thought, according to new research.
The study: Negative Outcome Charles Bonnet Syndrome, conducted by King’s College London in conjunction with the Macular Society, documented the experiences of 492 visually impaired people who had experienced visual hallucinations.
Charles Bonnet Syndrome is widely considered by the medical profession to be benign and short-lived. However, the research shows that 80 per cent of respondents had hallucinations for five years or more and 32 per cent found them predominantly unpleasant, distressing and negative.
The study published online in the British Journal of Ophthalmology, described this group of people as having “negative outcome Charles Bonnet Syndrome”. The group was more likely to have frequent, fear inducing, longer duration hallucinations, which affected daily activities.
They were also more likely to attribute hallucinations to serious mental illness and less likely to have been warned about the possibility of hallucinations before they started.
Worryingly, 36 per cent of respondents who discussed the issue with a medical professional said the professional was “unsure or did not know” about the diagnosis.
People with macular disease are particularly prone to Charles Bonnet hallucinations. They are thought to be a reaction of the brain to the loss of visual stimulation. More than half of people with severe sight loss experience them but do not tell others in case they are regarded as mentally ill.
The Macular Society is now raising awareness of Charles Bonnet Syndrome, so that people with sight loss know what to expect and why it is happening.
Dr Dominic Ffytche, clinical senior lecturer at King's College London's Institute of Psychiatry led the research. He said: “Charles Bonnet Syndrome has been traditionally thought of as benign. 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, 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.”
Tony Rucinski, Chief Executive, Macular Society, said: “It is essential that people affected by sight loss are given information about Charles Bonnet Syndrome at diagnosis or soon after."