A survey by research charity Fight for Sight has found that almost one in five respondents with sight loss and half of those with severe sight loss have experienced visual hallucinations.
Known as Charles Bonnet syndrome (CBS), visual hallucinations are a common side-effect of sight loss, in which people see things that are not there - it can often be mistakenly confused with the onset of dementia.
The condition is currently being featured as a storyline on Coronation Street with character Johnny Connors experiencing hallucinations as his eyesight slowly deteriorates.
Chief Executive of Fight for Sight, Sherine Krause, said: "Charles Bonnet syndrome is a complex and devastating side effect of sight loss. It is an area of research that little is known about and has largely been neglected."
Fight for Sight surveyed 290 UK adults in the survey and discovered that of those that experienced CBS, 20% said it impacts their mental health, and four in ten people said it affected their lives daily. There is currently not enough data to show how many people in the UK have CBS, but it is estimated to be hundreds of thousands.
Karren, realised she was experiencing CBS about four years ago, after a period of significant sight loss. She said: "I will be walking down the street and I'll see a small dog in the road – to me it will be a very clear image of a dog. I'll start to panic because I think the dog might be in danger of getting hit by a car, and it'll take a few seconds for my brain to click that there's no dog, I'm having a hallucination. I am mindful of not going outdoors and navigating traffic if I am tired because this can make my CBS worse and impact on my judgement when crossing a busy road or getting out of the way for cyclists."
Fight for Sight is urgently calling for more funding to be invested in research for CBS, and are working together with other organisations to investigate the cause of visual hallucinations associated with CBS, in the hope of eventually finding a cure.