Coloured filters improve exclusion of perceptual noise in visually symptomatic dyslexics

Previous studies of visually symptomatic dyslexics have found that their contrast thresholds for pattern discrimination are the same as non‐dyslexics. However, when noise is added to the stimuli, contrast thresholds rise markedly in dyslexics compared with non‐dyslexics. This result could be due to impaired noise exclusion in dyslexics. Some dyslexics report a reduction in discomfort experienced while reading and show increased reading speed when using coloured lenses. We hypothesised that coloured lenses work by aiding noise exclusion. Thus the coloured lenses should help performance best under conditions of high visual noise. We measured contrast thresholds for discriminating symbols in the absence and presence of visual noise. The results showed that visually symptomatic dyslexics, who otherwise had elevated contrast thresholds for discriminating symbols in visual noise, had thresholds similar to non‐dyslexics when wearing coloured filters. These findings provide evidence that in visually symptomatic dyslexics coloured filters can improve noise exclusion to normal levels.