Charles Bonnet syndrome affects people who've lost most or all of their eyesight.

Who's affected and why?

Charles Bonnet syndrome affects people who've lost most or all of their eyesight.

It's more likely to occur if the loss of vision affects both eyes.

According to the Macular Society, up to half of all people with macular degeneration – a gradual loss of central vision – may experience Charles Bonnet hallucinations at some time.

It's thought there are more than 100,000 cases in the UK.

People of any age can be affected by Charles Bonnet hallucinations, but they tend to occur later in life after a person starts to lose their sight. The hallucinations often begin when a person's sight suddenly deteriorates.  People who may have lost a lot of their vision from an eye condition such as cataract, glaucoma or diabetic eye disease

The main cause of Charles Bonnet syndrome is thought to be vision loss and how the brain reacts to it. It's not clear how loss of vision leads to hallucinations, but research is beginning to help us better understand the relationship between the eyes and the brain. 

When a person starts to lose their sight, their brain doesn't receive as much information as it used to. It's thought the brain sometimes responds by filling in the gaps with fantasy patterns or images that it's stored. These stored images are experienced as hallucinations.

Many of these conditions are more common in older people so many people who have CBS are older. However, anyone of any age, including children, may develop this condition as any eye condition that causes sight loss can trigger CBS.

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.