Visual stress and dyslexia for the practising optometrist

11 May 2016
Volume 17, Issue 2

This paper looks at coloured filters, particularly coloured overlays, and their use in helping those with reading difficulties and a range of other disorders.


Visual stress should not be confused with dyslexia. It refers to symptoms of discomfort and perceptual distortion that have a neurological origin. Pattern 2 of the Pattern Glare Test can be used to elicit symptoms of visual stress, but pattern 3 is of relatively little clinical use. The symptoms sometimes remit with tints, but studies consistently show that tinting precision well within 0.07 in the CIE 1976 UCS diagram is necessary for optimal effect (see Precision is necessary – strong evidence is now available, below). An improvement in reading speed with filters (overlays or lenses) can be measured using the Wilkins Rate of Reading Test, and an increase in reading speed of 15% is likely to indicate an improvement that exceeds any due to random variation. Visual stress remains a controversial issue, partly because of the publicity surrounding untrialled methods and partly because of reviews that are partial.

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