What is Charles Bonnet syndrome (CBS)?

Charles Bonnet syndrome (CBS) is a condition that affects many people with sight loss and blindness, and causes them to experience visual hallucinations. The hallucinations are often distressing and continuous – the exact causes are still unknown.

There’s approximately 100,000 diagnosed cases of CBS in the UK. Up to half of all people with macular degeneration, a gradual loss of central vision, may experience CBS at some time, according to the Macular Society.

Currently, the only available therapy for this condition is medication, but these are not always effective and can cause severe side effects.

Symptoms of CBS

Hallucinations often begin when a person suddenly loses their sight. Visual hallucinations are a normal response the brain has to the loss of vision.

CBS isn’t widely known about, so people often worry that they are losing their mind and developing a serious mental health problem, as well as losing their sight. These hallucinations can often be distressing, and can cause practical problems like extra difficulty getting around as it makes it difficult to judge your surroundings.

Over time, the hallucinations often become shorter and less frequent.

Diagnosis of CBS

Contact your GP if you start to notice any type of hallucinations. There’s no specific test for CBS, so doctors usually diagnose it by:

  • talking to the person affected about their symptoms
  • taking a detailed medical history
  • in some cases, carrying out tests to rule out other possible causes of hallucinations, such as Alzheimer's disease

If a person has recently lost their vision and are experiencing simple or complex hallucinations, with no signs of dementia or mental illness, they probably have Charles Bonnet syndrome.

Treatment of CBS

Currently, there is no cure for CBS. Medication, usually prescribed to treat epilepsy, Parkinson’s disease and dementia, can be effective to reduce the hallucinations. However these can cause serious side effects, so are only recommended to those with severe hallucinations.

It is possible to make the hallucinations easier to deal with. Firstly by understanding that the hallucinations are a normal result of sight loss and not a sign of mental illness.

Talking about your hallucinations and how they make you feel with your friends, family, GP, optician or ophthalmologist can help. Although CBS isn't a mental health condition, many mental health professionals have experience of helping people come to terms with hallucinations.

There are some practical things that have been shown to help some patients, these include:

  • changing the lighting conditions to see if it disappears
  • moving your eyes from side to side once every second for 15 seconds, pause, then repeat up to 4 or 5 times
  • stare at the image, then blink rapidly, or try to touch the vision
  • move around or perform a task to distract your brain
  • getting enough sleep is important, as the hallucinations may be worse if you are tired or stressed
  • some people overcome their fear by getting to know the figures in their visions.

Find out how Assistive Technology helps to manage tasks made difficult by low vision and blindness.

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