Postscript to -The trials they don't want you to know about (1)

As a follow up to their paper published in 2011 Ritchie and colleagues published a study looking at the subjects of their first trial, one year on.

Ritchie SJ, Sala S Della, McIntosh RD. Irlencolored filters in the classroom: A 1‐year follow‐up. Mind Brain Educ. 2012Jun;6(2):74–80.

Though not as rigorous as their previous study, outlined in my last post, it does contain some fascinating data that does nothing to support the use of of colour to treat the overlap group with poor reading and visual stress. I suspect it was a bit of an afterthought put together following criticisms of their first study - that benefits would not be seen without longer term follow up.
In the first study an Irlen screener diagnosed 47 out of 61 poor readers with 'visual stress'.
Those 47 children were then tested with prescribed overlay and placebo overlay and no difference in the rate of reading using the WRRT or reading naturalistic text measured with the Gray Oral Reading Test (GORT).
After 12 months 22 out of 47 of the original sample were still using colour in some form and 18 of these were still available to study. So this was a highly selected group who passed two criteria for visual stress; the Irlen screening tests and voluntary sustained us of overlays. According to their teachers this group had used overlays or lenses for a substantial part of the time. For this reason, if coloured overlays are effective, you would expect to see real world improvements in reading in this group.
Unfortunately the controls were a group of poor readers without visual stress from the previous study. The authors ackowledge that the ideal control group would have been individuals with visual stress who had been treated with a placebo overlay.
The visual stress group was tested with the WRRT using prescribed filter, placebo filter and clear filter. In short this part of the study was a crossover or within subject design.
The other test used was the Gray Oral Reading test which is a standardised reading test that measures accuracy and rate of reading and crucially, questions to test comprehension are included. The outcome is standardised for age to produce the Oral Reading Quotient (ORQ). This means that  if a subject progresses normally for age the ORQ should remain the same. If there is a catch up in reading, as predicted by proponents of the treatment of visual stress, the ORQ should improve and then perhaps stabilise.
Results
 The WRRT. No surprises here really. There was no significant difference in reading rate between presecribed overlay, placebo overlay and clear overlay.

GORT Oral Reading Quotient ORQ
Figure two on the right shows that for both groups, the Irlen wearers and the controls, the ORQ declined over the study period. This occured in spite of imrovements in WRRT for both groups bringing in to doubt the validity of WRRT as a reading test.



Conclusions
The authors are good scientists who are careful not to over-interpret their study and they also acknowledge its weaknesses. In particular the small sample size and the lack of a visual stress control group. Nonetheless it is one of the few studies to take a longer term look at outcomes in a group where a difference might be expected to be found. That is, those with visual stress diagnosed by an Irlen-screener and who pass the criterion of voluntary sustained use over 12 months. In spite of perceived subjective benefit no improvement in real world reading was seen.