Meares-Irlen or Scotopic Sensitivity Syndrome ' refers to visual perceptual disorder(s) affecting primarily reading and writing based activities.
Its existence is not recognized by some major medical organizations including the American Academy of Pediatrics, the American Academy of Ophthalmology, and the American Optometric Association.
However, it has been studied in the former Applied Psychology Unit, Cambridge, UK. The Scottish Parliament has also funded a research and treatment centre at the Glasgow Caledonian University.

People who have Irlen Syndrome see the page differently because of distortions of the print or white background

Some people who are labelled "dyslexic/dyspraxic" may actually be sufferers from Irlen

For those with dyslexia however....
What all good web designers are aware of is that creative use of colour and contrast can dramatically enhance the accessibility of a website.

It can be as important for people with sight problems as it is to people who have dyslexia or whose first language is not the main language of the site.

Everyone benefits from text which is both easy on the eye and that is easy to follow.

For example, people with dyslexia benefit from good contrast I find black or dark blue on white the best) as this can help make the structure of words and sentances easier to understand.

This is very true for me as I have a food intolerance and sometimes have had to request shop staff to read some food labels printed in coloured inks on coloured backgrounds - embarassing :)

As for those road atlas that print road numbers in yellow on green - arghhhhhhhhh! :)