Conflicting theories about Visual Stress

In his comment on my (fairly) recent post on “academic arguments and anecdotal evidence”, Philip Jones referred to the conflicting views of two academics, namely Professors Arnold Wilkins and John Stein, who put forth differing theories on the neurological causes of Visual Stress. I appreciated Philip’s comment: I don’t agree with him, but it’s interesting on a site like this to hear what other people have to say.

I am not a scientist myself – I used to be a  schoolteacher, and now I run a business, and I have to admit that I very quickly feel out of my depth in scientific discussions. As I have already made clear: if a lot of people, with no axe to grind, all report a common experience (in this case that, for some people, reading through colour alleviates distortions and discomfort when reading), then for me that is more real than analysis and more analysis of data. If you fly high enough above a forest to see the whole landscape, you lose sight of the trees that make it up – but it doesn’t mean they are no longer there.

Anyway – conflicting theories. Unfortunately I haven’t got time (no, really!) to explain them at the moment, but Wilkins (Essex University) suggests that Visual Stress is caused by “Cortical Hyperexcitablility”, and Stein (Oxford) theorises that the cause is “Magnocellular deficit”. The Cortical Hyperexcitablility model proposes that the correct tint to alleviate visual stress in an individual can be one from a wide range of colours across the spectrum; the  Magnocellular Deficit model suggests that the only colours that “work” are blue and yellow.

We (Crossbow Education) sell coloured overlays – thousands of them, every year. Our records of colours selected by thousands of customers consistently show, year on year, practically the same percentage of our ten tints sold. The figures are so consistent that they have statistical significance.  By far the biggest number sold are blue and yellow, but the point is that we sell thousands of the others as well – purple, pink, green etc.Visual Stress is perceived as a syndrome (often known as “Meares-Irlen syndrome), that is a collection of signs and symptoms that are observed in, and characteristic of, a single condition. Right now I have an itch on my leg. My skin is in an irritated condition. Is it caused by my varicose vein (yes I am that old)? Am I reacting to the detergent my wife used when she washed these trousers? Do I have an insect bite? These are all real causes of an irritated skin condition, and there are many more.

Generalising very broadly, there are more than twice as many people using blue and yellow overlays that any other colour. Is it possible that there is a condition called Magnocellular Deficit, which causes the symptoms of visual stress and which is remedied by reading through yellow or blue coloured overlays, and another condition called Cortical Hyperexcitability, also causing the same symptoms, and which is remedied by reading through a wide range of colours which also includes blue and yellow?

Arnold Wilkins and John Stein are men of great intelligence and integrity, who have come to their conclusions through thorough and painstaking research. As I said, I am not a scientist; but rather than seeing their conflicting explanations as cancelling each other out – and therefore destroying the scientific validity of using coloured overlays and tinted lenses to improve reading experience – I think that they could both be right. There isn’t just one scientific reason why reading through colour appears to benefit about 20% of the population to varying degrees: there are two.

Bob Hext, 10 Feb 2015

2 thoughts on “Conflicting theories about Visual Stress

  1. Thanks Bob
    As ever, an interesting post.
    While I share your respect for Arnold Wilkins and John Stein there are other highly respected scientists who have reached different conclusions. Sometimes citing eminent scientists is known as ‘eminence based practice’. Although even here I would argue that you are ‘outgunned’. These days evidence based practice is more highly respected. Studies are selected according to methodological criteria that minimise the risk of bias -so called systematic reviews. This is the type of methodology favoured by NICE or the Cochrane collaboration for example.
    Ignoring the issue of whether either of the speculative neuroscientific theories is correct- that is cortical hyperexcitability or abnormal processing of the magnocellular pathways; what is lacking is empirical evidence that the use of colour aids reading or the acquisition of reading among dyslexics who also have visual stress. There have been two systematic reviews (as opposed to narrative reviews) published in the area. Both commented on the methodological shortcoming of much of the research and concluded that it did not support the use of colour lenses and overlays in the overlap group with visual stress and dyslexia(1)(2).
    You argue that the Stein approach and precision tinting approach both work (according to their promoters) because they are converging on the same colours blue and yellow. However, this is not backed up by published series and does not explain why two mutually contradictory theories should both seem to work –according to their advocates.
    Kriss and Evans for example found a preference for mint green overlays(3). On the other hand Ritchie and colleagues found Aqua and blue where most favoured and yellow almost never used(4). I find this lack of consistency across studies odd.
    Once again thanks for your great post. I am reviewing some of the key trials that are said to support the treatment of visual stress in dyslexia at http://visualstresssceptic.blogspot.com I hope you will take a look and perhaps comment.

    1. Albon E, Adi Y, Hyde C, West Midlands Health Technology Assessment Collaboration. The effectiveness and cost-effectiveness of coloured filters for reading disability: a systematic review. Studley: West Midlands Health Technology Assessment Collaboration, Dept. of Public Health and Epidemiology, University of Birmingham; 2008.
    2. Galuschka K, Ise E, Krick K, Schulte-Körne G. Effectiveness of Treatment Approaches for Children and Adolescents with Reading Disabilities: A Meta-Analysis of Randomized Controlled Trials. Lidzba K, editor. PLoS ONE. 2014 Feb 26;9(2):e89900.
    3. Kriss I, Evans BJW. The relationship between dyslexia and Meares-Irlen Syndrome. J Res Read. 2005 Aug;28(3):350–64.
    4. Ritchie SJ, Della Sala S, McIntosh RD. Irlen colored overlays do not alleviate reading difficulties. Pediatrics. 2011 Oct;128(4):e932–8.

  2. Thanks for your post Philip. My thoughts on the convergence of the Stein and Wilkins research are of course totally speculative, and I agree – the lack of consistency between findings on specific colour use is odd. But at the end of the day we live in a wonderful diverse universe: will we ever be able to explain more than a small percentage of its richness? And my problem remains – in fact I met her again when I did a talk for Leicester Dyslexia Association on Wednesday night. Her name this week was Mia: she couldn’t even see the text on my powerpoint, let alone read it, until I put a coloured background behind it…

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