Essex University – Professor Wilkins
Colored overlays have been shown to reduce visual stress and increase reading speed on the Rate of Reading Test (meaningless text in which common words are presented in random order). The increase occurs only when a sufficient number of colors is available from which to choose the optimum, which differs from one individual to another. A variety of controlled trials have shown that placebo effects are not a sufficient explanation for the increase in reading speed. Coloredglasses have been shown to reduce headaches in open trials and also in two small-scale trials using a double-masked protocol. The color optimal for overlays differs from that optimal in lenses. Imaging studies of patients with migraine have shown that it is only when the shade is precise that a reduction in an otherwise abnormally large blood oxygenation occurs. Given the general association between elevated blood oxygenation and visual discomfort, this tends to support other evidence that a precise shade may be necessary for a beneficial clinical effect. Visual discomfort and perceptual distortions and the benefit from color are sometimes collectively referred to as ‘visual stress’ (preferred) or ‘Meares-Irlen Syndrome’, and sometimes as ‘Irlen Syndrome’ (USA), or (formerly) ‘scotopicsensitivity syndrome’, a misnomer.