What is Visual Stress

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Visual stress (sometimes called 'Meares-Irlen Syndrome' or 'Scotopic Sensitivity Syndrome') is the experience of unpleasant visual symptoms when reading, especially for prolonged periods. Symptoms include illusions of shape, movement and colour in the text, distortions of the print, loss of print clarity, and general visual irritation. Visual stress can also cause sore eyes, headaches, frequent loss of place when reading, and impaired comprehension.

Simulation of one sympton of visual stress

Visual stress can have an adverse effect on the development of reading skills, especially reading fluency - i.e. the ability to recognise words quickly and to read longer passages text of text in a smooth and efficient way so that good comprehension is maintained. Visual stress makes reading an unpleasant and irritating activity that children will tend to avoid as much as possible. Research has shown that 15 - 20% of people suffer visual stress to some extent, and they also tend to be hypersensitive to fluorescent lighting and flicker on computer monitors.

The condition of visual stress was first discovered independently by Olive Meares, a teacher in New Zealand, in 1980, and by Helen Irlen, a psychologist in the United States in 1983. They did not use the term 'visual stress', but they recognized that the problem contributed significantly to reading difficulties and that coloured overlays can help to overcome the unpleasant symptoms. The use of tinted lenses or coloured overlays to treat visual stress was formerly regarded with scepticism by the medical and education professions. However, scientific studies in the 1990s by Professor Arnold Wilkins of the University of Essex have shown that this treatment is generally the most effective and simplest solution.

For more information on research by Professor Arnold Wilkins on visual stress visit:

or consult:
'Reading Through Colour:
How Coloured Filters Can Reduce Reading Difficulty, Eye Strain, and Headaches' by Arnold Wilkins. Wiley, 2003. ISBN: 0-470-85116-3.


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