Author's reply

We thank Evans & Allen for their letter regarding our editorial and welcome the opportunity to have an open discussion regarding the issue of coloured filters and their link with reading. We completely agree that children with reading problems are best managed by optometrists (rather than Irlen diagnosticians, for example) as they can determine whether ametropia or binocular vision issues could improve any reading difficulties. In their letter, Evans and Allen comment on our interpretation of the Conway et al. study. However, the results from the Conway et al. study seem very clear: girls much preferred pink, rose and purple lenses (52 of 124, 42%) compared to boys (29 of 120, 24%) and this is not a “relatively minor contribution” as the figure is almost double and contributes nearly half the colour choices for girls. Indeed, while Conway et al. suggest that blue is a male colour preference, much of the recent colour preference literature suggests otherwise, including the two most highly cited papers, both appearing in high quality journals. They suggest a natural universal preference for blue for both sexes perhaps due to associations with clear blue skies and clear water. On top of this universal preference for blue, there is a female preference for pink and possibly purple. It would be interesting if Conway et al. re-analysed their data and determine for all patients except those who chose pink, rose and purple, whether blue colours are more popular than other colours for both sexes. Such analysis would be useful in terms of better understanding this complex area as colour preferences may also be influenced by favourite sports teams and no doubt other factors. Our interpretation of the research evidence supports the assertion by Evans and Allen that the colour required to treat ‘Visual Stress’ does not need to be precise. However, we believe that this is not clear to many clinicians (or academics), particularly given that the lenses linked with the Intuitive system are highly specialised and called ‘Precision Tinted Lenses’. Evans & Allen’s argument that various earlier studies didn’t really include patients with Visual Stress is problematic, given there still seems to be no agreed definition regarding what constitutes ‘Visual Stress’ despite Precision Tinted Lenses being prescribed for at least 15 years. On a positive note, we welcome a recent paper by one of the authors that attempts to develop guidelines for diagnosing ‘Visual Stress’, which suggests that it can be diagnosed if the patient shows three of six typical symptoms and two of three signs. However, two of these signs involve improvements with coloured overlays and diagnoses determined by treatment success are clearly open to placebo effects. In addition, even this limited definition is not definitive: the authors advise that this “diagnostic tool” is “preliminary and it is recommended that experienced clinicians interpret this flexibly” and it “is a starting point for future research to test this, and other variations, using retrospective and prospective clinical data”. This ongoing lack of a definition leads to confusion in the area and makes it challenging to interpret research outcomes, given it could be argued that poor repeatability or poor treatment gains in studies were because the participants involved didn’t really have ‘Visual Stress’. Finally, we concur with Evans & Allen and others conclusion that what is required is a definitive randomised controlled trial, with methodology, analyses and outcome measures agreed by researchers and clinicians from both sides of the argument. This would provide clearer insight into this controversial area and provide the basis for clinicians and patients alike to make informed decisions regarding coloured filters.