Visual Stress/Irlen Syndrome Research
The causes of visual stress are currently unknown; there is no scientific explanation for the symptoms, however it is commonly agreed to be a visual-perceptual problem. Its perceptual nature means that it cannot be corrected with glasses as it is believed to stem from the visual cortex of the brain.
Using Colour Overlays
As it currently stands, the success of treatment for visual stress is debated. Research has come up with mixed results, with divided opinions on the benefits of using colour overlays on text. Presently some scientists believe colour overlays help those who experience visual stress and dyslexia. Interestingly, one study in 2005 found that 37.5% of children with dyslexia were affected by visual stress, whilst 25% of non dyslexic children were affected by it. There are those who believe dyslexia and visual stress are related in some ways.
According to a 1999 study by Evans et al, 80% of people who used coloured overlays on text found benefits from using them. Another study in 2001 found that children with dyslexia who were allowed to pick their own coloured overlay saw a reading speed increase of 25%. This has been argued however in a recent 2015 study whereby the author discredits the theory that dyslexia is caused by visual problems, meaning that coloured overlays will not reduce the symptoms. They suggest there was very little difference in performance of visual tests between dyslexic and non-dyslexic children.
Despite this, many people and children make use of coloured overlays when experiencing visual stress.
Different Coloured Overlays
It is commonly believed that a particular colour, hue and saturation will work best for each individual, i.e. an overlay that works for one person might not work as effectively for another. However, there appears to be no agreement on which coloured overlay works best as a whole.
What does this mean for treatment?
In essence, if a coloured overlay helps the symptoms of visual stress, the person affected is the best person to judge this. If no difference is experienced, they do not need to continue using them.
Irlen H. (1997). Reading problems and Irlen coloured lenses. Dyslexia Rev. Spring 4–7
Kriss, I. & Evans, B.J.W. (2005). The relationship between dyslexia and Meares-Irlen syndrome. Journal of Research in Reading, 28(3), 350–364.
Evans,B. J. W.,Patel,R.,Wilkins,A. J.,Lightstone,A., Eperjesi,F.,Speedwell,L. and Duffy,J. (1999) A review of the management of 323 consecutive patients seen in a specific learning difficulties clinic.
Wilkins, A.J., Lewis, E., Smith, F., Rowland, E., & Tweedie, W. (2001). Coloured overlays and their benefit for reading. Journal of Research in Reading, 24, 41 – 64.