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 .
Application of ChromaGen haploscopic lenses to patients with dyslexia: a double-masked, placebo-controlled trial.
BACKGROUND Many patients with dyslexia report distortion to text when they are reading . After a successful pilot trial of an improvement in reading rate using ChromaGen haploscopic filters in comparison with the Intuitive Colorimeter , a full-scale , r and omized , cross-over , double-masked , placebo-based trial was undertaken . METHOD The Wilkins rate of reading test was used to produce a baseline score , against which scores with ChromaGen lenses , placebo lenses , and a control were compared .  Exclusion criteria included no formal dyslexia diagnosis , contraindications to contact lens wear , and uncorrected visual causes for reading difficulty . RESULTS Forty-seven individuals successfully completed the trial , of which 41 reported distortion to the text ( e.g. , words appeared to move , were blurred , or patterns or spaces seemed to form in the text ) when the patients were reading , and nine were color deficient . A comparison trial of ChromaGen lenses with placebo lenses demonstrated a significant improvement in the reading rate with ChromaGen lenses in individuals who reported distortion to text ( p = 0.05 ) and a highly significant improvement in non-color-deficient individuals who reported distortion ( p = 0.006 ) . T-tests of the repeated measures showed that ChromaGen lenses produced a highly significant improvement in the rate of reading -- over and above the placebo -- in non-color-deficient individuals who reported distortion ( p < 0.0001 ) . CONCLUSION The significant increase in the reading rate amongst those who reported distortion suggests that by decreasing the distortion to text , a substantial proportion of dyslexic patients --in combination with their normal reading programs -- would benefit from this aid
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 .