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 .
Reading Disabilities and the Effects of Colored Filters
The efficacy of a controversial treatment , using colored filters to remediate reading disabilities , was measured empirically , with colored overlays placed over reading material on white paper . Irlen 's ( 1983 ) method is to prescribe specific tinted filters as lenses that she cl aims filter specific light frequencies and remove a range of perceptual disorders that adversely affect reading and related learning performance . Irlen calls this condition " scotopic sensitivity " and cl aims it is a significant factor in a high percentage of people with learning disabilities . Ninety-two children with significant reading disabilities were classified as either scotopic or nonscotopic using the Irlen Differential Perceptual Schedule , and were r and omly assigned to one of six treatment groups using colored or clear overlays .  Reading performance ( rate , accuracy , and comprehension ) as measured by the Neale Analysis of Reading Ability ( Neale , 1987 ) and the Formal Reading Inventory ( Wiederholt , 1986 ) improved significantly when the scotopic children read with the preferred colored overlay filter compared to clear or different-colored overlay filters . Nonscotopic children showed no change
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 .