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 .
Likelihood of Null Effects of Large NHLBI Clinical Trials Has Increased over Time
Background We explore whether the number of null results in large National Heart Lung , and Blood Institute ( NHLBI ) funded trials has increased over time . Methods We identified all large NHLBI supported RCTs between 1970 and 2012 evaluating drugs or dietary supplements for the treatment or prevention of cardiovascular disease . Trials were included if direct costs > $ 500,000/year , participants were adult humans , and the primary outcome was cardiovascular risk , disease or death .  The 55 trials meeting these criteria were coded for whether they were published prior to or after the year 2000 , whether they registered in clinical trials.gov prior to publication , used active or placebo comparator , and whether or not the trial had industry co-sponsorship . We tabulated whether the study reported a positive , negative , or null result on the primary outcome variable and for total mortality . Results 17 of 30 studies ( 57 % ) published prior to 2000 showed a significant benefit of intervention on the primary outcome in comparison to only 2 among the 25 ( 8 % ) trials published after 2000 ( χ2=12.2,df= 1 , p=0.0005 ) . There has been no change in the proportion of trials that compared treatment to placebo versus active comparator . Industry co-sponsorship was unrelated to the probability of reporting a significant benefit . Pre- registration in clinical trials.gov was strongly associated with the trend toward null findings . Conclusions The number NHLBI trials reporting positive results declined after the year 2000 . Prospect i ve declaration of outcomes in RCTs , and the adoption of transparent reporting st and ards , as required by clinical trials.gov , may have contributed to the trend toward null findings
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 .