What is Charles Bonnet syndrome (CBS)?

Charles Bonnet Syndrome (CBS) is not an eye condition in itself, but develops when someone of any age – including children - has lost over 60% of sight. CBS causes vivid, silent, visual hallucinations which range from disturbing to frightening. Images seen can be of simple patterns, animals, plants, insects, furniture, buildings, water, fire, humans – often in elaborate costumes – or whole scenes.

It is important to remember that CBS is not a mental health condition and that it is entirely due to loss of sight.

There are, at least, 1 million people in the UK who live with CBS. It is reported that up to half of all people with macular degeneration – a gradual loss of central vision – may experience CBS at some time.

CBS is now recognised in the World Health Organisation’s taxonomy of diseases and conditions. This means that it is considered a condition in its own right and not just a side effect of sight loss.

Why does it happen?

As sight diminishes, the regular messages from the eye to the brain slow down or stop. When this happens, the brain is left with nothing to interpret and, consequently, fires up to create its own images. What is seen depends on which part of the brain is firing at that moment.

The loss of sight can be caused by any eye disease (not just macular degeneration), or from a stroke, cancer, accident, diabetes, multiple sclerosis, or any other condition which damages the optic nerve.

Diagnosis of CBS

Awareness of CBS is growing but, currently, too few healthcare professionals have heard of the condition and mis-diagnosis can occur.

Most people with diminishing sight receive no warning about CBS from their ophthalmologist or optometrist, which can cause them significant distress when they start to experience hallucinations as a result of their sight loss. 

GPs should be contacted if any type of hallucination develops. The vivid, visual hallucinations caused by CBS are completely silent and no other sense is involved. If there are no other signs of dementia or mental illness, the diagnosis is most likely CBS. By contrast, if the hallucinations are accompanied by sound, taste, smell, or touch, hallucinations are being caused by another reason. 

As yet, there is no specific test for CBS so, sometimes, tests will be carried out to establish definitely that no other condition – such as  dementia – is present.

Diagnosis of CBS can be made by the GP, with help from an ophthalmologist, optometrist, neurologist, psychiatrist, eye clinic liaison officer or rehabilitation officer for the visually impaired.

Living with CBS

Sight loss itself can cause anxiety, fear and loneliness, but when CBS is added, the isolation – even from family members – can further worsen a person's quality of life. Living in a world of unpredictable, uninvited images – even if they are pleasant – can impact negatively on everyday life.

Researchers have proved that isolation, stress, and fever increase the number of CBS episodes and make the images more frightening. Judging surroundings – what is real and what is not – may become more difficult and caution is advised when moving or walking.

It is reported that medication taken for other conditions can also make CBS worse. It is therefore advisable for the GP to review all medication being taken by the patient.

Treatment of CBS

Currently, there is no cure for CBS, but researchers are working to learn more about this condition.

Coping strategies*

The coping strategies below have been reported as useful by some patients. They serve to distract the brain and keep it active. They do not work for everyone but hallucinations are often worse during a quiet time – sitting in a chair, as a passenger in a car or just before sleep.

  • Clap your hands.
  • Click your fingers.
  • Reach out to the hallucination.
  • Sing.
  • Whistle.
  • Stand up or sit down.
  • Walk about to a different room or part of the room.
  • Change the lighting.
  • Stare at the image.
  • Shine a torch upwards from the chin (not into the eyes).
  • Tip your head slowly to one side and then the other.
  • Blink a few times.
  • Switch on/off the tv, radio or music.
  • Move your eyes from side to side once every second for 15 seconds; pause; then repeat up to 4 or 5 times.

* Reproduced courtesy of Esme’s Umbrella’s, a CBS specialist charity. Additional advice is available on their website.

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