Abstract
The way citation distortion can create unfounded authority in a subject area is exemplified in the paper “Coloured filters to reduce the symptoms of visual stress in children with reading delay”, published early online in the Scandinavian Journal of Occupational Therapy. The diagnostic criteria for visual stress remain unclear, for which reason the prevalence figures should be viewed with scepticism. Randomized controlled trials with placebo control groups consistently show improvements in experimental and control lenses. This letter is a critical review of the evidence cited in the introduction to the paper. In the light of this the most likely explanation for their results is the placebo effect.
Key words:
I read with interest the early online publication “Coloured filters to reduce the symptoms of visual stress in children with reading delay” (Citation1).
In the introduction it is stated that visual stress occurs in 5–20% of the population. It is surprising that the only citation to support this assertion is to a charity website. Because the diagnosis of visual stress depends on vague and subjective symptoms and because there are no validated diagnostic tests, research on the prevalence of visual stress needs to be viewed with scepticism. In an ideal study the assessors would be blinded to the status of the subjects as poor readers or normal readers. The only such study diagnosed approximately 50% of normal readers and poor readers (Citation2).
Another study published in 2005 using the Wilkins Rate of Reading Test (WRRT) did find a higher prevalence of visual stress in subjects with dyslexia but this did not reach statistical significance and furthermore it was not a masked study and thus at risk of bias (Citation3). The relationship between so-called visual stress and reading difficulties is problematic and proponents have to explain why the overwhelming majority of people with so-called visual stress do not have reading difficulties.
Elsewhere in the introduction the authors state that “this type on intervention has been found to ease the discomfort experienced and improve reading accuracy”, citing two publications in support of this claim (Citation4,5). However, ignoring any issues of “cherry picking”, even these papers do not support these claims. The randomized controlled trial by Wilkins et al. was hampered by a high rate of dropout and showed no improvement in reading speed, accuracy, or comprehension compared with placebo in 45 out of 68 subjects. There was a small difference in terms of symptom diaries; however, data were only available for 36 out of 68 subjects. The study also contained conflicting data. When asked at the end of the study, 26 subjects preferred the control filter and 24 the experimental filter. The study by Robinson and Foreman published in 1999 showed that all groups improved over the study period but there was not a significant difference between experimental filter and blue or placebo filter. High claims of subjective benefit were noted in all groups, suggesting an effective placebo effect (Citation4).
The authors also fail to reference other negative randomized controlled trials (Citation6,7).
In citing the paper by Bouldoukian the authors do not mention that the very modest increase in reading speed was not for naturalistic text but for the jumbled words of the Wilkins Rate of Reading Test (WRRT) and the study did not include “attentional” controls (Citation8). Other studies have shown that increased reading speed of the WRRT produced with coloured overlays is neither sustained nor matched by improvements in reading naturalistic text (Citation9).
It is stated that the American Academy of Pediatrics does not advocate the use of colour. However, this was a combined statement from the American Academy for Pediatrics, Council for Children with Disabilities, American Academy of Ophthalmology, American Association for Pediatric Ophthalmology and Strabismus, and the American Association of Certified Orthoptists (Citation10) and thus carries rather more weight.
Although the authors acknowledge that the use of colour to treat the symptoms of visual stress is a contentious issue they fail to reference the only two systematic reviews on the subject, neither of which supports the use of colour to treat visual stress when it coexists with dyslexia (Citation11,12).
The way citation distortion can create unfounded authority has been well studied (Citation13) and is exemplified in the introduction section of this paper.
In the methods section the authors state “it was ethically unjustified to use a control group as no benefit had been achieved with placebo filters”. The authors cite one of their own publications in support of this (Citation14). However, this study did not even contain a placebo control group. Randomized controlled trials consistently show that placebo control groups do just as well as those with the experimental lens (Citation4-6).
Given that studies consistently show improvements in both experimental and placebo lens groups, the most likely explanation of the results reported in the study is the placebo effect.
Declaration of interest: The author reports no conflicts of interest. The author alone is responsible for the content and writing of the paper.
References
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