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Irlen Syndrome

This is part of my pages on Typeface or Font Readability and in particular the issue of readability of text for people with reading difficulties. This page is not really to do with fonts, it comments on the issue of Irlen Syndrome.
Evidence, see, seems to indicate that many people, not just those with dyslexia but also others who find reading to be a harsh experience, find a passage of text easier to read through a coloured filter or coloured spectacles. This is especially associated with a perceptual condition known as Irlen Syndrome.
Those who treat reading problems using coloured filters or glasses consistently report encouraging results, though it seems that no one yet knows why it should work. One effect of the filter will be to reduce the relative brightness of text against background, and it may be interesting to know whether text in a shade of grey, as opposed to text in black, on white paper has a similar effect, or whether black text printed on grey paper, or even on coloured paper, is equivalent. So far I can find no indication that anyone has asked the question, it’s all believed to be due to colour.
There is an academic study on the use of coloured filters for reading at Ophthal. Physiol. Opt. 2002 22 55–60. As with many academic studies, this one is obsessed with the results of the trials and on being academically rigorous, without seeming to be able to to stand back and ask the question: why?
The assessment for the coloured filters is sometimes done by adjusting the background colour on the computer screen, but looking at text through a filter will adjust the foreground colour too, which adjusting the background colour on the computer screen will not. You can (with modern web browsers) simulate a transparent overlay. You should be able to do that on this page by switching on the font changer which then appears in the leftmost column. That is not doing exactly the same thing as placing a filter in front of a printed page, though the perceptual effect is fairly similar. Of course with the overlay simulation on screen you won’t get any ambient light reflection, which with a physical filter, however anti-glare, there will always be some. More questions then.
All this seems to point to a relative brightness issue, more than one that is specifically related to colour, though obviously if you are a questioning digger like me more research is still to be done.
As anyone knows who has sat and read a newspaper under a tungsten or fluorescent lamp – ie just about everyone – adjusting the colour of the ambient light is something we soon get used to and don’t perceive as especially different from daylight conditions. So the reading through coloured filters is awash with questions. Obviously if it helps, then that’s good, and perhaps it’s only mean logical teeth-grinders such as me who want to question the science.


Anonymous said...


I work in a reprographics unit in a college and we get requests for coloured overlays all the time for use by students with reading difficulties. The most popular colours requested are green, yellow and pink. There doesn't seem to be a universal colour which works well for everyone.

Great article, I would like to know if grey text on white makes any difference too. Next time we get a request in I'll do some research....

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