Charles Bonnet syndrome (CBS) is a common condition among people who have lost their sight. It causes people who have lost a lot of vision to see things that aren’t really there, known as visual hallucinations.
People who have CBS may have lost a lot of their vision from an eye condition, such as age-related macular degeneration, cataract, glaucoma or diabetic eye disease.
It’s thought that there are more than 100,000 cases of CBS in the UK. Some research suggests that up to 60 per cent of people who are experiencing serious sight loss may develop it.
The main cause of CBS is loss of vision and how your brain reacts to this loss. Current research seems to suggest that when 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 is not receiving as much information from your eyes as it used to. Your brain can sometimes fill in these gaps by releasing new fantasy pictures, patterns or old pictures that it has stored. When this occurs, you experience these images stored in your brain as hallucinations.
There are some medical problems, such as Parkinson’s disease, Alzheimer’s disease, strokes, serious mental illness and other brain conditions, which affect the part of the brain concerned with seeing and these conditions may cause some people to have hallucinations.
Certain things about CBS hallucinations make them different to the hallucinations caused by other conditions. Usually, with CBS you’re aware – or can learn to recognise – that what you’re seeing isn’t real, although it may appear vivid. CBS hallucinations only affect your sight, which means that you don’t hear, smell or feel things that aren’t there. People with CBS do not develop any obvious, complicated non- medical explanation about the cause of their hallucinations (sometimes called “delusions”). For example, someone with CBS wouldn’t have thoughts that the people they were seeing wanted to hurt them.
The visual hallucinations caused by CBS can vary and can range from simple shapes and dots of colours, simple patterns, straight lines or a network of branches, to detailed pictures of people, animals, insects, landscapes and buildings. When you have lost a large amount of your vision it may be difficult to see everyday things, but you may find that your CBS hallucinations are very detailed, and much clearer than your normal vision. The images can appear “out of the blue”, lasting for just a few minutes or in some cases, several hours.
At times, the hallucinations may fit alongside the background you are looking at, making them feel quite real, like seeing cows in a field when the field is actually empty or seeing a fence across the pavement. At other times, they will seem totally unreal, like seeing fantasy images such as dragons.
The kinds of things people see with CBS hallucinations seem to fall into two broad types:
• simple repeated patterns
• complex hallucinations of people, objects and landscapes.
Both kinds of hallucination can vary. Sometimes they may be in black and white and at other times in colour, or they may move or stay still. It’s possible you may have one type of hallucination more than another or have both types of hallucination at the same time or one after another.
Simple repeating pattern hallucinations
Many people with CBS experience hallucinations of repeating patterns. These may be grids or shapes or lines, which can be quite vivid in colour, like bright green dots surrounded by vibrant pink squares. You may also see complicated brickwork or mosaic patterns that grow in size to cover more and more of your vision. People can also see patterns that look like a network of branches or roots from a tree, growing over everything they see.
People usually describe this type of hallucination as being laid on top of everything they see, or growing across any surface they look at. Sometimes people also experience patterns of distorted faces, which appear in their vision and can change shape or move towards them.
The second type of hallucination people can experience are more complicated and include hallucinations of people, places, insects and animals.You may experience hallucinations where whole scenes appear, such as landscapes with waterfalls, mountains or a garden full of flowers. At other times you may see individuals or groups of people. You may see people dressed in costume, like Edwardian families, Roman soldiers or small children in bonnets. The figures of people in your hallucinations may be life size, larger than life sized or very commonly very small. All these types of figures may move or remain still.
At times, the hallucinations may fit with the room that you are in when you experience them, so that you may see animals in your bed or people working in your garden. At other times the hallucinations can appear very odd, such as double-decker buses in your kitchen or hallway.
Dealing with hallucinations of space
You may find you have hallucinations that change the shape of streets and rooms. For instance, your hallucinations might suddenly make it look like there is a wall or fence in front of you and you may have to check if this is real. This can make you lose confidence walking around and it may take you longer to get out and about.
If you experience hallucinations like this, it’s important that you are not afraid to check the area around you. It may be sensible to go slowly, to reach out and feel around for what is real and what is not.
Dealing with hallucinations of people
Hallucinations of people can be frightening, particularly if they’re inside your home. If the images are of very small people or people in costumes then it may be easier to realise that they are hallucinations than if the figure is in ordinary clothes. Having a good idea of when you’re likely to have visitors may make you more confident if you have this type of hallucination and will help in you feeling secure in your home or your surroundings.
Dealing with hallucinations of animals
Hallucinations of animals are also very common. Often people describe animals on their chairs or in their bed. Sometimes this can be very upsetting, especially if you aren’t keen on a particular type of animal.
Using touch to make sure that the animals are hallucinations is not a bad thing and sometimes reaching out towards the hallucination may cause them to stop and disappear.