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 .
A comparison of two-coloured filter systems for treating visual reading difficulties
Abstract Purpose : Visual disturbances that make it difficult to read text are often termed “ visual stress ” . Coloured filters in spectacles may help some children overcome reading problems that are often caused by visual stress . It has been suggested that for optimal effect each child requires an individually prescribed colour for each eye , as determined in systems such as the “ Harris Foundation ” coloured filters . Alternatively , it has been argued that only blue or yellow filters , as used in the “ Dyslexia Research Trust ” ( DRT ) filter system , are necessary to affect the underlying physiology . Method : A r and omised , double blind trial with 73 delayed readers , was undertaken to compare changes in reading and spelling as well as irregular and non-word reading skills after 3 months of wearing either the Harris or the DRT filters . Results : Reading improved significantly after wearing either type of filter ( t = −8.4 , p < 0.01 ) , with 40 % of the children improving their reading age by 6 months or more during the 3 month trial . However , spelling ability ( t = 2.1 , p = 0.05 ) and non-word reading ( f = 4.7 , p < 0.05 ) improved significantly more with the DRT than with the Harris filters . Conclusion : Education and rehabilitation professionals should therefore , consider coloured filters as an effective intervention for delayed readers experiencing visual stress . Implication s for Rehabilitation Any disability that impacts on a child ’s capacity to read has serious implication s for academic development as well as the ability to participate independently in activities of daily living . One reading disability , generally termed “ visual stress ” , is related to visual disturbances that make it difficult to read text . This research demonstrates the beneficial use of coloured filters for promoting visual reading capacity for children with visual stress . Professionals who are involved in the needs of children with reading delay , may like to consider the benefits that coloured filters can afford children with visual reading problems
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 .