A group of eye charities are funding two research projects at Cardiff University and University of Oxford to investigate the cause of the visual hallucinations associated with Charles Bonnet Syndrome, with the hope of eventually finding a cure.

Charles Bonnet Syndrome is estimated to affect hundreds of thousands of people in the UK, but the condition is often misunderstood and can sometimes be mistakenly confused with the onset of dementia.

Fight for Sight, together with partners Blind Veterans UK, Esme's Umbrella and Health and Care Research Wales, hope to provide insight into the cause of Charles Bonnet syndrome hallucinations, which will help inform larger studies in the future and eventually to test whether there are interventions to help improve the condition.

What is Charles Bonnet syndrome?

Charles Bonnet syndrome is a common side-effect of sight loss in which people experience visual hallucinations. These hallucinations include simple repeated patterns or shapes, such as grids or brickwork patterns or complex hallucinations of people, objects and landscapes.

These can vary from benign to quite alarming and the images appear very suddenly, lasting for just a few minutes or in some cases, several hours.

It can happen to people with good mental health who have no history of psychiatric problems. Usually, people with Charles Bonnet syndrome are aware – or can learn to recognise – that what they’re seeing isn’t real even though it’s very vivid.

New research projects for Charles Bonnet Syndrome

A team of researchers at Cardiff University, funded by Fight for Sight and Health and Care Research Wales has developed a novel method to induce controlled hallucinations in the lab, which will allow them to explore the mechanisms underlying Charles Bonnet Syndrome.

This project will use fully-sighted people to investigate the possibility that peripheral (‘side’) vision is more ‘suggestible’ than central vision. The team are testing a hypothesis that following long-term central vision loss, patients with Charles Bonnet Syndrome pay more attention to their peripheral vision, which is more reliant on expectation and previous experience than central vision, and therefore prone to hallucinatory experiences.

The project at the University of Oxford is funded by Fight for Sight, Blind Veterans UK and Esme’s Umbrella, will use MRI scans to compare the brains of people with and without Charles Bonnet syndrome to look at how they differ. In particular they will measure the levels of chemicals in the visual areas of the brain to see whether they are abnormal in CBS, leading to the hallucinations.

Chief Executive of Fight for Sight, Sherine Krause said: “So much more needs to be done to understand Charles Bonnet syndrome. This is an area of research that little is known about and has largely been neglected, so we are very pleased to fund these two important research studies. With a better understanding of the causes of Charles Bonnet syndrome, we will be one step closer to developing a treatment and eventually a cure for the condition. This is just one area where much greater investment in eye research is needed to ensure we can continue transforming the lives of people with sight loss.”