Abstracts of Scientific Papers

• Visual stress in adults with and without dyslexia
• Visual factors in reading
• Visual search as a predictor of susceptibility to visual stress in reading
• Computerised screening for visual stress in reading
• Computerised screening for visual stress in children with dyslexia

Visual stress in adults with and without dyslexia

Abstract

The relationship between dyslexia and visual stress (sometimes known as Meares-Irlen syndrome) is uncertain. While some theorists have hypothesised an aetiological link between the two conditions, mediated by the magnocellular visual system, at the present time the predominant theories of dyslexia and visual stress see them as distinct, unrelated conditions, a view that has received some support from studies with children. Studies of visual stress in adults are rare, yet recent reports of a high incidence of this phenomenon amongst university students with diagnosed dyslexia call for further investigation of the issue. This study sought to clarify the relationship between visual stress and dyslexia by comparing the reading performance of dyslexic and non-dyslexic adults with, and without, colour. Degree of susceptibility visual stress was determined by means of a symptom rating scale. Optimal colour was determined using an Intuitive Colorimeter, which was also employed to assess reading speed under the two experimental conditions. Only the dyslexic students with high visual stress showed significant gains in reading speed when using optimal colour. The use of response to treatment (rather than symptomatology) as a diagnostic criterion for visual stress is criticised, especially when applied to adults, as this may give misleading findings. On the basis of reported symptomatology, students who experience high levels of visual stress are more likely to show improvements in reading rate with optimal colour if they also have dyslexia than if they do not have dyslexia. Although not establishing an aetiological link, these findings imply an interaction between the two conditions with major implications for theory, diagnosis and treatment.

Visual factors in reading

Abstract

This article reviews current knowledge about how the visual system recognises letters and words, and the impact on reading when parts of the visual system malfunction. The physiology of eye and brain places important constraints on how we process text, and the efficient organisation of the neurocognitive systems involved is not inherent but depend on the experience of learning to read. Although studies have reported that many children with severe reading difficulties have problems with visual fixation of words, in this context the concept of 'visual dyslexia' remains controversial. Evidence that a significant proportion of children with dyslexia have impairment of the magnocellular component of visual system (which responds to contrast and movement) has led to alternative theories challenging the phonological deficit model of dyslexia. Deficits in the magno system have also been proposed to explain symptoms of visual stress that many people experience when reading, and to account for the alleviation of these symptoms by use of coloured overlays or tinted lenses. However, a competing theory that posits cortical hypersensitivity to pattern glare as the cause of visual stress is generally more favoured at the present time. Our scientific understanding of reading would be much improved if visual factors were better integrated into theories that currently focus almost exclusively on phonological factors, but some progress towards this is being made.

Visual search as a predictor of susceptibility to visual stress in reading

Abstract

Visual stress is the subjective experience of unpleasant visual symptoms during reading. Diagnosis is often based on the immediate improvement in reading speed with a coloured overlay on Wilkins Rate of Reading Test (WRRT). Visual stress sufferers have been found to be impaired on visual search, especially in the presence of repetitive striped geometric patterns. In this study, children whose response times were significantly affected by a visually stressful pattern during reading-like visual search had significant increases in reading rate with an overlay compared to children whose response times were not affected by the pattern. Contrary to expectation, visual stress susceptibility did not affect response times for non-visually stressful visual search. The results suggest that visual search task may provide a more appropriate and objective method for classification of visual stress in children.

Computerised screening for visual stress in reading

Abstract

Visual stress is the experience of unpleasant visual symptoms when reading. There is currently no objective diagnostic test for this condition, which affects a substantial proportion of the population and which can disrupt development of reading skills. The reliability of subjective reports of symptoms has been questioned, especially where children are concerned. Diagnosis by positive response to the preferred treatment method, either the sustained voluntary use of a coloured overlay or immediate improvement in reading rate when using an overlay, is usually regarded as the best option. Recent research has reported that children who are significantly impaired by a visually stressful pattern during reading-like visual search are more likely to show significant improvement in reading speed when using an overlay. This study was designed to evaluate a prototype computerised visual stress screener that incorporated visual search. The results confirmed that primary and secondary school children who were classified by the screener as having high susceptibility to visual stress had larger percent increases in reading rate with an overlay compared to those with low visual stress. The results also indicated that subjective reports of symptoms may not always be diagnostically effective with younger populations. It was concluded that screening for visual stress in reading using a computerised visual search task is an educationally promising development.

Computerised screening for visual stress in children with dyslexia

Abstract

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 computerised 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 percent 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 percent 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.