Charles Bonnet syndrome
What is it?
Charles Bonnet syndrome is a common side-effect of sight loss in which people see things that are not there (visual hallucinations). The hallucinations can be very clear, detailed and consistent and can happen to people with good mental health. More than 100,000 people in the UK are thought to have Charles Bonnet syndrome.
We don't know exactly what causes Charles Bonnet syndrome but it's more likely
- with severe sight loss or blindness, especially in both eyes
- in older people
- when people are socially isolated
- after vision gets worse suddenly
Although eyes are the sensors that respond to light, it's the brain that does the seeing. The brain receives information from the eyes and decodes it into the picture we see.
If the brain stops receiving information, it can fill in the gaps with its own images. So it's possible that Charles Bonnet syndrome is similar to the feeling of having a 'phantom limb' that can be experienced by people who lose an arm or a leg.
If you have Charles Bonnet syndrome it does not mean that you have dementia or a serious mental illness.
Common hallucinations experienced by people with Charles Bonnet syndrome include seeing repeating patterns and shapes, people and faces, animals, landscapes and objects, and cartoon images in bright colours.
Hallucinations may last for seconds or hours over a period of days or years. They may happen less often as time goes on.
People experiencing the hallucinations will usually know that what they are seeing is not really there. Other senses, such as smell, hearing, taste and touch are not affected.
At the moment there is no specific cure for Charles Bonnet syndrome, but it is possible to make it easier to deal with. It can help to understand that the hallucinations are a normal result of sight loss and not a sign of mental illness.
It may also be helpful to talk to family or friends and to your GP or eye doctor, especially if the hallucinations are getting in the way of day to day life. Medications may help if the hallucinations are distressing. There may also be some simple practical things to do when they start such as changing the lighting or what you are doing at the time. Eye movements can help stop a troubling hallucination while it occurs.
Further information on Charles Bonnet Syndrome can be found on the Esme’s Umbrella website: http://www.charlesbonnetsyndrome.uk/.
Last updated November 2016
Approved by Dr Dominic ffytche, King’s College London