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Posted 29th April, 2011 by admin

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A diagnosis of dyslexia is significant, for all concerned. As specialist assessors, we already know that full diagnosis is compromised, if the functionality of vision is impaired. However it seems to me that lots of us have never been given the opportunity to understand in more detail. Only through better understanding can we really inform and improve our practice, and articulate these issues to learners and often cynical bystanders. Even the medical profession are often unaware of the implications of visual interference, with regard to reading efficiency, whether or not any individual is dyslexic.

I recently visited Aston University’s Vision Sciences Department, during a learner and vision clinic. They specialise in finding and treating eye problems associated with specific learning difficulties and headaches. As a not-for –profit operation, they offer an excellent referral point, throughout the academic year. Most of us, as part of assessment, look for the symptoms of visual stress and experiment with overlays, to diagnose. Aston Vision Sciences would generally suggest a 3 tiered approach, which I would advocate we translate into our own practice;

  1. Does the candidate need reading glasses? …..Assessment loses validity if reading glasses are lost or forgotten. It may be inconvenient, especially if working for an external client, but the assessment should not proceed. Patoss, as voiced by Anwen Jones, recommends these standards.
  2. If print distortion and/or reading fatigue are apparent, with reading glasses worn if prescribed, binocular co-ordination rather than visual stress may be the issue. This would be remediated by eye exercises, not coloured overlays. Therefore we still need to refer to a specialist optometrist, but we need to make it clear that colour is not always the way forward. We also need to take on board that reading scores would be compromised, even with experimental acetates. Covering one eye may elucidate diagnosis.
  3. Only at this stage should visual stress, Meares Irlen Syndrome, be investigated further. The alternative term, scotopic sensitivity, now seems to be considered a misnomer. Visual Stress refers to reading difficulties, light sensitivity and headaches from exposure to disturbing visual patterns.

Our readers may complain of symptoms; however they may also be unaware that others do not suffer the same interference, or degree of interference. We need to be proactive and look for signs:

The Golden Rules…

v  Ask open questions… ‘Are the letters moving or still?’  Don’t prejudice assessment.

v  Recognise that people who suffer visual stress may have poor assimilation of reading   content, tire quickly and the quality of their work may deteriorate rapidly. Concentration may be poor. Co –morbidity with dyslexia is high, but the behaviours may be similar, resulting in an increased chance of misdiagnosing the degree of visual processing difficulties associated with dyslexia.


Blurred/ dancing print, misty/coloured surrounds, rivers/worms through words, fading/darkening letters, resizing/shifting letters and letters falling off the page/line.


Frequently pulling away from the page, or changing position, tracking with fingers, rubbing eyes and blinking excessively, yawning and fatigue after reading, slow halting reading, a reluctance to read and even low self- esteem.

If the reader is more fluent and comfortable when the page is covered by a coloured sheet of acetate, we recognise that visual stress may well be impacting. Generally referral to a specialist optometrist would involve normal and binocular tests, followed by acetate testing, several weeks of experimental use and finally working with an intuitive colorimeter machine, to determine the precise optimum shade of remedial glasses. Because of the distances between script and the eyes, overlays and computer background colours are likely to match, it is therefore reasonable for us to recommend such intervention for normal study and examination access arrangements. However as visual stress is related to the processing of the written and other external visual stimuli, glass lens colour may well be a very different colour.  Overlays provide a surface colour whereas lenses bring about a change in the colour of a light source.

In conclusion, most practitioners would argue that visual stress is a different condition to dyslexia. We may not have all the answers, but we know enough to recognise that it is also higher amongst dyslexics. Informed estimates seem to lie around it affecting, to varying degrees, about 20% of the general population, but 35-40% of dyslexics. This comorbidity is likely to result in a ‘double whammy’ effect. If we think about it, we already take on board that poor reading efficiency, with a lack of automaticity, means that a dyslexic reader will often have to look longer and harder. This extended effort is likely to make them more sensitive to the physical characteristics of print.

And a closing thought. We can remain confident in the assessment process; if we work holistically. If we look to identify dyslexia as a pervasive condition, impacting on working memory, the manipulation of words and a variety of information processing tasks, reading efficiency (whether or not visual stress impacts) provides only one perspective in the assessment process.

Yvonne Gateley

April 2011

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  • Jocelyn Gronow

    Working with adults and children who are dyslexic, it became apparent, that many had unrecognised difficulties of maintaining a clear image of text on a page, during a reading session.
    During the assessment process, it was disturbing to realise that not only were they unable to use their visual strengths due to the visual stress caused by looking at a page of black text on a white background, but some were also unable to distinguish sounds accurately, because they had additional auditory processing problems.
    The fact that these individuals had learnt to read at all was remarkable; a tribute to their hard work and determination. Sadly, the combined difficulties resulted in a lack of fluency when reading and an ability to read only in short bursts, severely hampering their educational development and achievement.
    So, it is important that assessment by a specialist optometrist be combined with an assessment by a specialist teacher which identifies strengths and weaknesses and recommends appropriate support. Multi-sensory assistive technology can be extremely beneficial, particularly when it is part of a personal learning package.

  • Andylittleford

      I have been “diagnosed” with Irlens syndrome and benefited greatly from some lenses, after MANY years of problems, due to an RTA.

      I now cannot afford further lenses and so am in search of help, any ideas please? xx

    • suepartridge

       Andy – thank you for your comment. I will email you with some ideas of where you can get help.  In the meantime, check out the link to a list of specialist optometrists.  You can find it in the news item on our home page.

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