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 .
Scotopic Sensitivity/Irlen Syndrome and the Use of Coloured Filters: A Long-Term Placebo-Controlled Study of Reading Strategies Using Analysis of Miscue
This study investigated the long-term effects of using coloured filters on the frequency and type of errors in oral reading . A double-masked , placebo-controlled crossover experimental design was used , with subjects being assessed over a period of 20 months . There were three experimental groups ( Placebo tints , Blue tints , and Diagnosed tints ) involving 113 subjects with reading difficulties , ranging in age from 9.2 yr to 13.1 yr . The 35 controls ( ranging in age from 9.4 yr . to 12.9 yr . ) had reading difficulties but did not require coloured filters . There was a significant improvement for all groups in the accuracy of miscues over the period , although experimental groups over-all did not improve at a significantly different rate than the control group . The failure to find significantly greater improvement for the experimental groups over the control group for the total period , despite subjects ' reports of improved print clarity , may be partly related to the lack of effective letter-sound analysis and synthesis skills and to the use of a word- identification strategy of guessing based on partial visual analysis
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 .