At least a million Britons suffer from a little-known condition that causes terrifying hallucinations.

But this condition is not caused by mental health problems or dementia. This is solely due to a loss of vision that has reduced or stopped regular communications from the eyes to the brain.

This left the brain with nothing to interpret. Consequently, it lights up and creates images of its own, ranging from disturbing to terrifying.

Of those professionals who know about it, a tenth admit that they have very limited understanding, and half (51%) would like to know more.

More than a quarter (28 percent) would not feel confident diagnosing a patient with the disease.

And 78 percent would like to first rule out mental illness or dementia before diagnosing a patient with CBS, even if they believe that’s what they’re experiencing.

But of medical examiners unfamiliar with CBS, one in ten (11 percent) even recalls visits from patients who showed symptoms of the disease.

CBS is widespread among blind and visually impaired people, and studies show that about one in five people with vision loss develop it, meaning that at least one million people in the UK are currently living with the condition.

However, the disease is not taught in medical schools, and more than three-quarters (78 percent) believe it should be given more attention in obtaining a medical degree or qualification.

The study was conducted by Esme’s Umbrella, the only charity in the UK that offers support to those living with CBS and their families.

One of the volunteers, Nina Chesworth, who has yet to be diagnosed after four and a half years, spoke about her experience with the condition.

She said: “I first started experiencing CBS symptoms right after I lost sight in my left eye following a traumatic incident.

“When I woke up after the operation, I saw a lot of bright colors, but they just told me that it was my mind that was playing a cruel joke on me.

“Over time, the colors began to turn into shapes, and then into ghostly images – Picasso-style faces, zombies and animals.

“It got so intense and frightening that I researched what the visions could mean – and it wasn’t until I found out about Esme’s umbrella and contacted them that it started to make sense.

“The charity invited me to meet with Prof Dominic Ffitch, the UK’s lead researcher at CBS, and he told me all about this disease and I was able to talk to other people who had also experienced it.

“But my visions became more and more complex and I couldn’t cope anymore – at this point I was talking to my therapist, but they didn’t hear anything about it.

“That was four and a half years ago and I still haven’t been officially diagnosed.

“My ophthalmologist didn’t make a diagnosis either, and after visiting several specialists, they all had different views on what it could be and what caused it.

“Only one said he would consider CBS after I told them what it was.

“It was Dominic and Esme’s umbrella that gave me a real understanding of why this is happening and what to expect.

“It was a huge relief to learn that this is not a mental health issue, but a possible natural consequence of vision loss. It made me feel confident again to handle my situation.”

The study also found that one in four respondents were unaware of the only CBS specialist clinic in the UK, located in London.

And nearly a fifth (19 percent) do not know where to go for care of a CBS patient outside of the health service.

Another 27% would not feel comfortable suggesting coping strategies for a patient who is experiencing hallucinations.

But when it comes to a condition like CBS, 83 percent think it’s important for the patient’s family to have a complete understanding of what their loved one is going through.

Consequently, 86 percent make an effort to refer families to charities to support them, and 88 percent will refer those who have been diagnosed to specialized organizations.

And overall, eight out of ten (79 percent) think charities can play an important role in supporting patients with illnesses, OnePoll found.

Judith Potts, founder of Esme’s Umbrella, said: “While awareness of CBS is starting to improve, there is still a clear knowledge gap about it.

“And as a result, stories like Nina’s are still all too common in the blind and visually impaired communities where they have a really hard time getting a diagnosis of CBS.

“Especially during times when people are told they may have mental illness or dementia, this can often cause a lot of unnecessary levels of stress.

“That’s why at Esme’s Umbrella, we want to do our part to ensure that everyone living with CBS has access to support, as well as a network of others with life experience to help them cope with the symptoms of the disease.”