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 and Masked Study of Reading Achievement and Perception of Ability
This study investigated the effects of using coloured filters on reading speed , accuracy , and comprehension as well as on perception of academic ability . A double-masked , placebo-controlled crossover design was used , with subjects being assessed over a period of 20 mo . There were three treatment groups ( Placebo filters , Blue filters , and Optimal filters ) involving 113 subjects with “ reading difficulties ” , ranging in age from 9.2 yr . to 13.1 yr . and with an average discrepancy between chronological age and reading age of 1.8 yr . The 35 controls ( who did not use coloured filters ) ranged in age from 9.4 yr . to 12 9 yr . , with an average discrepancy between chronological age and reading age of 21 yr The treatment groups increased at a significantly greater rate than the control group in reading accuracy and reading comprehension but not for speed of reading . For self-reported perception of academic ability , two of the three treatment groups showed significantly greater increases than the control group . The larger improvements for treatment groups in reading comprehension may be related to a reduction in print and background distortions allowing attention to be directed to the processing of continuous text rather than to the identification of individual words . A reduction in print distortion , however , may not be sufficient to generate improved word- identification skills without additional remedial support , and this may be indicated by the nonsignificant increase in rate of reading
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 .