While many studies report improvements with coloured lenses , the effect size is generally small and /or similar to the improvement found with a placebo condition .
Consistent with previous review s and advice from several professional bodies , we conclude that the use of coloured lenses or overlays to ameliorate reading difficulties can not be endorsed and that any benefits reported by individuals in clinical setting s are likely to be the result of placebo , practice or Hawthorne effects
PURPOSE There are many anecdotal cl aims and research reports that coloured lenses and overlays improve  reading performance .
Here we present the results of a systematic review of this literature and examine the quality of the evidence .
Computerized screening for visual stress in children with dyslexia.
Visual stress-a condition in which unpleasant visual symptoms are experienced when reading-has been reported to be more prevalent in dyslexic individuals but at the present time the relationship between dyslexia and visual stress remains controversial . ViSS , a computerized visual stress screener that incorporates reading-like visual search , has recently shown promise in studies with unselected sample s of primary and secondary school children . This study investigated the use of ViSS with dyslexic children . Dyslexic children identified as having high visual stress showed significantly higher per cent increases in reading rate with a coloured overlay and reported significantly higher critical symptoms of visual stress , compared to dyslexic children with low visual stress . The same results were found for reading-age controls , indicating that ViSS can be equally effective with normal readers as well as with children with dyslexia . Compared to reading-age controls , dyslexic children were found to have significantly higher susceptibility to visual stress , significantly larger per cent increases in reading rate with an overlay , and significantly higher critical and non-critical symptoms of visual stress . Extrapolated to unselected population sample s , the data also suggest that visual stress is more likely to be found in people with dyslexia than in people who do not have dyslexia . These results , which point to an important link between the two conditions , are discussed in relation to current theories that attribute visual stress to either a magnocellular dysfunction or cortical hyperexcitability
While many studies report improvements with coloured lenses , the effect size is generally small and /or similar to the improvement found with a placebo condition .
Consistent with previous review s and advice from several professional bodies , we conclude that the use of coloured lenses or overlays to ameliorate reading difficulties can not be endorsed and that any benefits reported by individuals in clinical setting s are likely to be the result of placebo , practice or Hawthorne effects
PURPOSE There are many anecdotal cl aims and research reports that coloured lenses and overlays improve  reading performance .
Here we present the results of a systematic review of this literature and examine the quality of the evidence .