Before Christmas 2024, I had never heard the term visual stress. It didn’t sound like something I needed to worry about. Then, at a work event, I met Kimberley Harrison, CEO of Cerium Visual Technologies (CVT), a UK company that helps a specific group of children and adults struggling to read due to visual stress.
Kimberley explained, visual stress can make reading black text on a white background uncomfortable and difficult. Smaller text can make things even harder, with words and letters appearing to be moving around. As we were chatting, I had one of those real lightbulb moments: what she was describing sounded exactly like my 10-year-old daughter’s reading habit.
Ever since my daughter started school at the age of four, my husband always felt her reading was different. She would mispronounce words because she sounded them out differently. As time went on, he kept saying to me that she might be dyslexic. I was never fully convinced, because she did not struggle with some of the more typical signs. She could follow steps, her reading comprehension was great, and she always passed her school fluency tests, even though she may not get the top mark but it was still a pass.
What is visual stress? Signs a child may struggle to read black text on a white background
Visual stress is a condition that can affect reading comfort and visual processing. For some children or adult, black text on a white background can feel overwhelming (like my daughter). Words may appear to move, blur or jump around, and small text is even more challenging.
After that conversation with Kimberley, my husband and I started paying much closer attention to our daughter’s reading habits. She had very little interest in reading, and the only books she enjoyed or willing to read were below her age range because the words were bigger. I had assumed that was laziness, but then I started to question everything and question myself a lot as a mother. Why and how did I not pick this up sooner?
How the Intuitive Colorimeter test helped identify visual stress
CVT is licensed to manufacture and distribute the Intuitive Colorimeter, a machine used to test the exact colour a patient needs to eliminate their visual stress. During 100% Optical 2025, I took my daughter with me because she wanted to see what mummy does for work. I knew CVT was exhibiting and they had an Intuitive Colorimeter on the stand, so I asked whether they could do a quick test on her knowing the results would not be accurate because the normal environment for the examination has to be conducted in a dark room.
The brief test was done by Claire Millar, managing director of CVT, who has a degree in clinical optometry. I was told that colorimetry testing is usually carried out by qualified optometrists, orthoptists and other eye care professionals with specific training in visual stress assessment. Even though it was not conducted in the right environment, the result suggested there was a significant likelihood that my daughter was experiencing visual stress.
Honestly, it felt like a huge weight had lifted. We finally had a possible explanation and, more importantly, a way to support her.
How the Intuitive Colorimeter test helped identify visual stress
Visual stress assessment: our next steps after the first test
Soon after the exhibition, I asked Kimberley to recommend a CVT client of hers who could carry out a more thorough examination. Cole Martin Tregaskis was recommended to me as one of the best visual stress specialists in our area. At this point I feel very lucky to work in my field. This makes it so much easier to find the right help.
My daughter had a two-part consultation, with each session about two weeks apart. The first one included a full eye examination, followed by testing with colour filters to see which colours might relieve her visual stress the most. During that session, it was narrowed down to three possible colours. The specialist then did a series of reading tests, first without filters and then with them, to see which colour improved her reading speed the most. The colour she needed was a shade of purple.
After that, we were advised to use an A4-sized plastic purple filter which closely matched to her identified colour, while reading for the next four weeks. This was to help confirm whether she really needed it. The specialist explained that some children may simply pick their favourite colour, which of course gives them no real help at all. She also pointed out that once a child notices the difference, they can become very aware of how much it helps, especially my daughter being 10.
Originally, the specialist suggested four weeks because my daughter was just below the 15% threshold with her reading speed sitting at 14.7%, placing her within the acceptable range for visual stress. However, I wasn’t going to accept that because I saw how much the coloured sheet was helping her; therefore, I asked for a follow-up sooner, and we agreed on two weeks. By then, my daughter was completely reliant on the A4 coloured sheet. So much so, that once she forgot to take it to school and she asked the school to call me to drop it off for her. Her teacher noticed an improvement in her reading fluency, and for the first time in her life, the letters stopped “jumping around”, which meant she could read accurately.
How the Intuitive Colorimeter test helped identify visual stress
Why precision matters with coloured lenses for visual stress
The second part of the assessment used the CVT machine in a more detailed way, based on my daughter’s responses about her experience with the filters. The machine was calibrated to match the colour of her coloured sheet, and then she was tested with slightly different shades of purple to see how her eyes responded.
Some shades were a little more red, others a little more blue, all to pinpoint the exact tone that would give her the greatest result to elevate her visual stress.
The machine then produced a series of codes specifying the exact shades of purple she needed. These were used to select different lens tints from a CVT lens case. They were placed into a temporary pair of plastic glasses, which she wore under normal lighting conditions to assess whether they relieved or worsened her visual stress. She tried five different shades of purple. To the naked eye, they were hard to tell apart, but under light, the differences were there if you look really hard.
How the Intuitive Colorimeter test helped identify visual stress
I must admit, that level of care and precision really blew me away. Kimberley later explained why it matters:
“Precision is key because even small deviations in hue or saturation can significantly alter the therapeutic effect of the lenses for some patients.”
I had not realised that generic coloured lenses simply would not do. They need to be tailored exactly to the patient’s needs. The chosen shade was a darker purple with a stronger blue tone, and that proved to be the best colour for my daughter.
I was also told that once the optimal colour is identified using the Colorimeter, it is digitally mapped and matched with over 10,000 possible colour combinations. Each pair of lenses is manufactured using a controlled, spectrophotometrically verified dyeing process to ensure the final tint precisely matches the prescribed specification. That explains why my daughter’s glasses have made such a difference. They are not just purple, they are her purple, for her visual stress.
Visual stress vs dyslexia: understanding the difference
One of the biggest things I learned through this experience is that visual stress is often confused with dyslexia because there can be some overlap. Dyslexia is a language-based learning difficulty, while visual stress affects the processing and comfort of visual input.
With dyslexia, a person may struggle with decoding words, sounding them out, retaining information, organising letters and numbers, and understanding text. People with dyslexia may also experience visual stress, but not everyone with visual stress is dyslexic, and that was very clear in my daughter’s case.
She did not show the broader signs of dyslexia. Her main difficulty was reading smaller words and reading black text on a white background. If the words were larger, she could read them perfectly fine. She also spelt “beautiful” in about five different ways because the letters often seemed to jump around, making it hard to remember the correct spelling. She simply assumed that was how everyone saw words and read, she did not know any difference.
I was keen to share what I had learned with my daughter’s school, especially the difference between visual stress and dyslexia, because so many families may not know visual stress exists. Another girl in my daughter’s class had the same issue and now wears orange-tinted lenses. If parents are unaware of visual stress, they may not realise that optical professionals could actually help.
Advice for opticians and parents: spotting the signs of visual stress early
For eyecare professionals, I really do think there is value in asking a child during a routine eye examination whether they find it hard to read black and white text, or whether letters seem to move around. Those two simple questions could help flag visual stress and open the door to a conversation and where further help can be given.
For parents, I would also say this: if a child seems bright, understands what they read (comprehension), but avoids books, struggles with smaller text or says letters move on the page, it may be worth exploring visual stress further before assuming it is dyslexia, as schools are often quick to make that assumption, often due to their lack of awareness regarding visual stress.
Life after diagnosis: how visual stress glasses changed my daughter’s reading
My daughter has been wearing her glasses for nine months now, and I can honestly say they have made a significant difference. She is now reading books that are appropriate for her age and, even better, she is actually enjoying them. She willingly picks up a book, which is something I had never seen before.
Her schoolwork has improved dramatically too. She can spell better and complete her work quicker than before. I asked the school to test her one month after she got her new glasses, and the results were beyond what I expected. In a two-minute reading test, she not only finished the required passage quickly, but also read beyond what was expected in the fluency test.
Visual stress vs dyslexia: understanding the difference
Recently, as the school prepared for her Year 6 SATs, I requested an assessment of her reading fluency again. She is doing so well that she is now exceeding expectations for her SATs reading paper. It is truly incredible to see and something I didn’t think would be possible a year ago.
Looking back, I wish I had known about visual stress sooner. I cannot help but feel guilty, the mum’s guilt is very real when I think about how long she struggled, it fills me with sadness.
Final thoughts
I am so grateful for that conversation at Christmas with Kimberely, for the support we received from Kimberely’s team and eyecare professionals at Cole Martin Tregaskis, and most of all for the way my daughter now lights up when she reads, does her homework and learns lines for her performing arts class.
This journey has changed everything for her and for us as a family. It has improved her confidence with her learning, and as parents, we can finally stop worrying and stressing because deep down we knew her full potential was not out in force, it wasn’t because she was lazy. She simply cannot read comfortably.
I really hope by sharing our story, it helps open up more conversations between patients, parents, schools and optical professionals. Simple steps can be taken to detect visual stress, and unfortunately, a standard vision test will not pick that up. If you are a parent reading this, ask your child if words or letters seem to jump around when they read. If you are an eyecare professional, you can ask your patient the same question. Starting the conversation is that simple. My daughter believed that the way she saw words and letters moving was how everyone read. She didn’t know any differently after all, that was simply how she had always read and perceived the world.
Notes: We paid in full for the CVT service with no discounts for diagnosis. The only gift we received was a frame from the STEPPER Start range. The total cost for the two consultations, A4 plastic filters and CVT lenses was GBP 380.