UK researchers have discovered that passing a weak electrical current between electrodes on a person’s scalp may lead to a reduction in frequency of the visual hallucinations experienced by some people living with sight loss.
As vision deteriorates, the visual cortex (the part of the brain responsible for processing sight) experiences a reduction in input from the eyes. It sometimes responds to the relative lack of stimulation by generating hallucinations that may consist of simple repeated patterns or complex images. This phenomenon, known as Charles Bonnet Syndrome (CBS), is caused directly by failing eyesight, not by a mental health problem or dementia, but can be very distressing. You can find out more about CBS by listening to our webinar.
Researchers at Newcastle University and King’s College London investigated whether gentle stimulation of the visual cortex, via electrodes placed on the scalp, might dampen down hallucinations for people experiencing CBS. Their study involved 16 people with CBS, who underwent daily 30 minute sessions of treatment, at home, on four consecutive days.
The study participants generally experienced a significant reduction in the frequency, but not the duration, of their hallucinations in the days following treatment. There were no adverse effects on remaining vision, and no serious side effects – the most common reported side effect was a tingling sensation at the site of the electrodes during treatment.
The researchers believe that their results warrant a further, larger-scale study to confirm the findings and explore factors such as the frequency and duration of treatment sessions. This additional trial data would be needed before the approach could be considered for general use.
Researcher Dr John-Paul Taylor, of Newcastle University, said: “We don’t unfortunately have any good treatments for CBS, and drugs which are typically used are often associated with significant side effects. We are excited by our initial findings that using a form of non-invasive brain stimulation, which was well-tolerated and can be delivered in a person’s own home, may reduce the frequency of visual hallucinations for people with CBS.”
Dr Dominic Ffytche, of King’s College London, highlighted that the intervention is not a cure. “CBS did not stop completely for anyone – but by reducing how often hallucinations occur, the hope is we can shift CBS from a highly distressing and unpleasant experience to something that no longer troubles you,” he said.
The research team published their findings in the journal Ophthalmology; the full paper can be accessed online at: https://www.aaojournal.org/article/S0161-6420(22)00502-4/fulltext.