When Hannah Louise Miller first put on a pair of purple-tinted glasses, her life was immediately transformed.

"It was like my whole world changed completely," she says. "Everything was so much better.

"My Irlen affects how I see the environment. I have depth perception issues and light sensitivity and I get headaches from it.

"It's not nice at all. These glasses help block out the bad light. They let me see everything better. Without the glasses I couldn't cope."

According to Irlen UK, the organisation for which 26-year-old Hannah is an ambassador, Irlen Syndrome is a desperately underdiagnosed "perceptual problem that affects the way the brain processes visual information."

They estimate that 12-15% of the population suffer from the symptoms of Irlen.

Many experience distortion in the environment, have severe difficulty reading, and as a result often develop behavioural problems.

Irlen awareness campaigners say such symptoms can be "easily treated" by wearing coloured filters/glasses "only available through an Irlen Centre" (Irlen UK)

Detractors argue there is little scientific basis for the existence of Irlen and that there is no evidence proving the efficacy of so-called 'Irlen filters'.

In the UK, Irlen diagnosis and treatment can only be received through one of nine nationwide Irlen Centres.

The process, which includes screening and diagnosis followed by yearly "re-tinting", costs thousands of pounds.

Writing for the British Medical Journal, a Consultant Ophthalmologist accused Irlen practitioners of exploiting and misleading patients.

But Irlen patients say their personal experiences beg to differ. They want to see Irlen treated by the NHS and screened for in schools.

"I know it's real because I'm dealing with it"

Hannah, who lives in Cogan, grew up being told she was intellectually disabled.

She attended various schools around Penarth, each of which she says struggled to cope with her inability to concentrate, absorb written information, and behave.

"I was naughty in the classroom because of how the light affected me," she says. "I couldn't handle the environment but didn't know why."

Hannah left school with no GCSEs and severe self-confidence issues.

She was severely bullied throughout childhood and struggled to relate to her peers.

In 2012, a college support worker noticed that Hannah had trouble copying from a whiteboard.

She suggested Hannah might have Irlen Syndrome and arranged a screening for her.

After taking various tests, Hannah was diagnosed and prescribed a pair of glasses with Irlen Spectral Filters.

She is now treated by Alan Penn, an "Irlen Practitioner" based in Derby. None of the UK's nine Irlen clinics are in Wales.

"Before I was diagnosed, I didn't really know that it was a problem because it was all I knew," she says.

"Then I put on the glasses and was like 'wow, I thought everyone saw like that'.

"I was shocked by how much of a difference it made. I finally understood why I was struggling."

Hannah is now taking a BSc (Hons) Top Up Animal Health and Welfare at Coleg Gwent.

She was made an ambassador for Irlen, speaking at a Welsh Assembly event and meeting Helen Irlen, the researcher who discovered the condition.

Receiving an Irlen diagnosis turned her life around.

"I want to help other people get diagnosed and try to get it into schools because they aren't picking it up. People need to be screened.

"Some people say it's not really, but it really is. Optometrists especially keep saying that but I know it's real because I'm dealing with it."

"No scientific evidence"

Hannah is right; Irlen-skeptics are abundant in the scientific community.

In 2011, a trio of researchers studied 47 schoolchildren diagnosed with Irlen for the Official Journal of American Academy of Pediatrics.

They concluded the following:

"We found no evidence for any immediate benefit of Irlen colored overlays as measured by the reading-rate test or the global reading measure."

In 2002, the Royal College of Ophthalmologists stated that "no scientific evidence to support the existence of such a syndrome has been found."

In 2018, the Royal Australian and New Zealand College of Ophthalmologists (RANZCO) reached the same conclusion.

In his aforementioned British Medical Journal opinion piece, Ophthalmologist Gwyn Samuel Williams did not hold back when he wrote:

"This is not harmless. The testimonials on the Irlen website include anxious parents battling with paediatricians over the correct treatment for their child, and patients are beginning to ask for these lenses to be provided on the NHS.

"The medical profession must be united in its stand against pseudoscientific nonsense such as Irlen syndrome."

However, some studies support the existence of Irlen syndrome and the use of lens treatment.

A Japanese study from 1990 urged international health bodies to recognise the syndrome.

The Irlen Institute says "more than 100" studies in reputable journals support "the use of colored overlays and lenses to treat the perceptual processing difficulties associated with Irlen Syndrome".

Among these, a study in the Korean Journal of Ophthalmology showed that reading improved by 20% in Irlen subjects wearing the tinted lenses.

Experience vs evidence

The brain has been described as science's final frontier. The organ responsible for understanding is comfortably the least understood.

No conclusive evidence has yet been found proving the efficacy of lens treatment or even the existence of the syndrome, which is why it is not screened for in schools or treated by the NHS.

In the absence of such evidence, how do we respond to personal experience? Should it alone be enough for the medical profession and policymakers to start taking Irlen seriously?

On the other hand, who are we to tell people like Hannah they are not experiencing that which they say they are?

Without further research, these questions will continue to go unanswered.