Computerized screening for visual stress in children with dyslexia.

Visual stress-a condition in which unpleasant visual symptoms are experienced when reading-has been reported to be more prevalent in dyslexic individuals but at the present time the relationship between dyslexia and visual stress remains controversial. ViSS, a computerized visual stress screener that incorporates reading-like visual search, has recently shown promise in studies with unselected samples of primary and secondary school children. This study investigated the use of ViSS with dyslexic children. Dyslexic children identified as having high visual stress showed significantly higher per cent increases in reading rate with a coloured overlay and reported significantly higher critical symptoms of visual stress, compared to dyslexic children with low visual stress. The same results were found for reading-age controls, indicating that ViSS can be equally effective with normal readers as well as with children with dyslexia. Compared to reading-age controls, dyslexic children were found to have significantly higher susceptibility to visual stress, significantly larger per cent increases in reading rate with an overlay, and significantly higher critical and non-critical symptoms of visual stress. Extrapolated to unselected population samples, the data also suggest that visual stress is more likely to be found in people with dyslexia than in people who do not have dyslexia. These results, which point to an important link between the two conditions, are discussed in relation to current theories that attribute visual stress to either a magnocellular dysfunction or cortical hyperexcitability.