Charles Bonnet syndrome

Understanding Charles Bonnet Syndrome

Charles Bonnet syndrome (CBS) is a common condition among people who’ve lost their sight.

It causes people who have lost a lot of vision to see things that aren’t really there – medically known as having a hallucination.

CBS hallucinations are only caused by sight loss and aren’t a sign that you have a mental health problem.

This page contains a summary of our information on CBS. To read our full information, download our Understanding Charles Bonnet syndrome guide, which is accredited by the Royal College of Ophthalmologists:

Download Understanding Charles Bonnet Syndrome in PDF

You can also download Understanding Charles Bonnet Syndrome in Word.


Quick links
– What causes CBS?
– What kinds of things might I see?
– What's it like to experience CBS?
– How will I know if I have CBS?
– Coping with CBS
– Further help and support



What causes CBS?

CBS is caused by loss of vision and the way your brain reacts to this loss.

When your sight is good and you are seeing real things around you, the information received from your eyes actually stops the brain from creating its own pictures. When you lose your sight, however, your brain isn’t receiving as much information from your eyes as it used to. Your brain can sometimes fill in these gaps by creating new fantasy pictures, patterns or pictures. When this happens, you experience these pictures as hallucinations. 

CBS tends to start in the weeks and months following a big deterioration in your sight.



What kinds of things might I see?

Your hallucinations can be of almost anything you can think of – they can range from simple patterns, shapes or colours, to vivid detailed pictures of people, animals, objects or buildings.

CBS hallucinations only affect your sight, which means that you don't hear, smell or feel things that aren't there. Usually with CBS you’re aware – or can learn to recognise – that what you’re seeing isn’t real even though it’s very vivid. People with CBS don’t usually develop complicated thoughts or ideas about why they are seeing things.

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What's it like to experience CBS?

Bee has glaucoma. She first experienced CBS when she was shopping. She explains the types of hallucinations she gets and how she copes.



How will I know if I have CBS?

If you start to notice any type of hallucination it’s important to make an appointment with your doctor as soon as you can.

There isn’t one test that your doctor can do to find out whether you have CBS or not. Your doctor will want to rule out other causes of hallucinations, usually by talking with you and in some cases, carrying out tests. If there are no signs of any other conditions that might be causing your hallucinations, and you have recently lost your sight, then it’s likely that your hallucinations could be caused by CBS.

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Coping with CBS

Currently there is no medical cure for CBS. Sometimes just knowing that the condition is not a mental health problem or a symptom of another disease can help a lot. Knowing that CBS usually improves with time (even if it doesn’t go away completely) and having information on CBS as well as sharing your experiences with friends or family can also help.

For most people there isn’t just one way to deal with their hallucinations, but there are a few things that you can try to do that may help. 

When you have a hallucination, you can try making some changes to the things around you and to what you are doing, to see if this will make your hallucination stop. Putting the TV or radio on, or standing up and moving around, or going into a different room can sometimes make the hallucination disappear. 

Some people also find that looking directly at the image they are seeing or reaching out to touch it causes it to fade. Sometimes moving your eyes or blinking rapidly can also help. 

Try a type of eye exercise where you move your eyes from left to right every second for 15-30 seconds, without moving your head. If the hallucinations continue, have a rest and try again. It’s unlikely to work if you’ve tried 4-5 times and the hallucination is still there. You might want to try again another time for a different type of hallucination.

Lighting conditions in certain rooms may also mean that you see the hallucinations more often in one room than another. If your hallucinations happen in dim light, then opening the curtains, turning on a light or the television may help. If your hallucinations happen when there’s a lot of light, then switching off a light may also help. 

Some people find that their CBS hallucinations are worse when they’re tired or stressed. Making sure you have enough sleep at night and having time to relax can help with this.



Further help and support

If you have CBS, you’re likely to have very poor vision, but there are a lot of things you can do to make the most of your remaining vision. This may mean making things bigger, using brighter lighting or using colour to make things easier to see. 

A low vision assessment can explore these things with you. Your GP, optometrist (also known as an optician) or ophthalmologist (also known as a hospital eye doctor) can refer you to your local low vision service for an assessment.

You can also find out tips for making the most of your sight by downloading our guide:

Helpful organisations

Esme's Umbrella is a campaign group to build up a greater awareness of Charles Bonnet syndrome, and NHS Choices has information and advice on Charles Bonnet syndrome.

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