Charles Bonnet syndrome and visual hallucinations

Charles Bonnet syndrome (CBS) is a condition causing visual hallucinations that can happen as a result of sight loss. Named after Charles Bonnet, the 18th century Swiss scientist and philosopher who first described the condition, these hallucinations can be very common in people with macular disease.

Hallucinations are the same experience as really seeing something, but the ‘something’ is not actually there. They can come and go unannounced, lasting for only a few seconds, or they can stay for a day or more. CBS itself can last from days to many years but, for most people, the hallucinations will improve with time and only happen occasionally.

Each person with CBS will experience seeing different things, which may be unsettling, frightening or even humorous. It’s important to remember that these hallucinations are not a sign of mental illness. 

What are the treatments for Charles Bonnet syndrome?

There are no treatments to stop hallucinations happening completely or remove hallucinations that appear. There is research looking to better understand the cause of CBS to find future treatments.

Research has investigated whether non-invasive brain stimulation may help those who have regular visual hallucinations. This project, funded by the Macular Society, tested a therapy called transcranial direct current simulation (tDCS). The research showed that tDCS therapy may help reduce the number of hallucinations patients experience. However, more work is needed to confirm these results.

Researchers are still investigating why some people with vision loss experience CBS, while others do not. There is also lots of research into how to stop hallucinations happening completely, or to get rid of them when they happen.

In rare cases, people with very distressing hallucinations may be offered medication to help with their CBS. These medications are usually prescribed for other conditions but have been shown to work for CBS hallucinations. A specialist doctor will usually prescribe these medications. The doctor will check to see if they are safe to use and rule out other causes of hallucinations.

It is important to make sure you’re well rested and sleeping well at night as hallucinations can be worse if you are stressed or tired.

Ways to stop a Charles Bonnet hallucination

There are a few recommendations on how to help stop hallucinations as they happen. These usually involve changing the visual input going to the brain, or disrupting the hallucinations.

These techniques include:

• Changing light levels i.e. moving from a light room to a dark room or vice versa or by turning on or off the lights
• Trying to touch the hallucination
• Eye movement exercises
• Shining a torch upwards from below the chin, making sure not to shine it into the eyes.

Eye movement exercise

1. Imagine two points about a metre (3ft) apart left and right on a wall in front of you. Stand about a metre and a half away and look from one point to the other once every second or faster for 15–30 seconds. Don’t move your head and keep your eyes open when looking left and right. Have a break of a few seconds.
2. If your hallucinations are still there, try repeating the exercise.
3. If they have not stopped after four or five attempts, the technique is unlikely to work. You may want to try again another time, or for a different hallucination.

When hallucinations may not be Charles Bonnet syndrome

Some characteristics may suggest that hallucinations could be caused by something other than CBS. These can include:

• Hearing voices, or seeing both voices and visions
• Hallucinations only of people and animals, without patterns, colours, shapes and lines
• Very detailed or elaborate explanations of what is seen or heard
• Feeling the need to call the police or an ambulance
• Not realising at the time that the hallucinations are not real
• Confusion or memory difficulties
• An accompanying person noticing the hallucinations more clearly than the person experiencing them.

If you notice any of these signs, please contact your GP or ophthalmologist for advice.

Support for you

We are here for you. While hallucinations can be unsettling, they are not usually a cause for concern. If you find them upsetting, you can speak to your doctor or ophthalmologist, or call our helpline on 0300 3030 111.

If you need further support, our counselling service can talk with you about the options available, including one-to-one support and other ways we can help.

For free, confidential advice and support, you can call our helpline on 0300 3030 111 (9am–5pm, Monday to Friday). You can also email help@macularsociety.org or make a referral for the helpline for yourself or a loved one, with their permission.