Positive results from Charles Bonnet study

Posted: Thursday 23 April 2020

A Macular Society-funded study into a potential treatment for Charles Bonnet Syndrome (CBS) in people with macular disease has reported some encouraging early results.

The project, ‘Treating visual hallucinations in people with macular degeneration: a non-invasive stimulation study’, has been carried out by researchers at Newcastle University and King’s College London. It explored whether a technique called transcranial direct current stimulation (tDCS) can be used to treat CBS. The technique involves passing a weak electric current between two pads placed on a person’s scalp and has been found to change activity levels in certain areas of the brain. Researchers were keen to investigate whether this treatment could decrease activity in areas of the brain which may be over-active in CBS and which may be contributing to causing visual hallucinations. It is the first time this technique has been tested on macular disease patients.

CBS hallucinations are experienced by up to half of all people with macular disease. They can be simple unformed flashes of light, colours or shapes, while many people also see geometrical grids and lattices. Other people have reported seeing disembodied heads, Edwardian people, snakes and other disturbing images. Around one third of people with CBS report that hallucinations can be distressing and cause disruption to their daily lives.

Although there is no current treatment for CBS, previous research suggests that loss of information from the eyes results in increased spontaneous activity in the visual areas of the brain, which contributes to the occurrence of visual hallucinations.

In a pilot study, six people diagnosed with CBS who experience continuous visual hallucinations throughout their waking hours were asked to attend King’s College London. They received non-invasive stimulation to the visual parts of the brain, designed to reduce over-activity. They were then asked to report how stimulation at different strengths and over different areas affected their visual hallucinations.

Positive improvements were reported by four out of the six participants, including reductions in the size and intensity of the visual hallucination images. The treatment was also well tolerated by all of the study participants, with no significant side effects reported.

Cathy Yelf, Macular Society chief executive, said: “While this is only the first study to test the effectiveness of tDCS as a possible treatment for CBS, the initial findings from this project do appear to be very encouraging.

“We often hear deeply distressing stories from people who have experienced unpleasant or upsetting CBS hallucinations, so any news of an effective potential treatment is always a positive thing.

“Continuing to invest in research projects like this is one of our top priorities. Research is the only way to build our knowledge and understanding of macular disease so that a cure can be found and this cruel and isolating condition can be beaten once and for all.”

The results of this pilot study have been used to inform further investigations testing the treatment on a larger number of people. The findings of these investigations are currently being analysed and will be announced later this year.

For more information about CBS, see our Charles Bonnet information.