Current Status of Treatments for Dyslexia: Critical Review

Ann W. Alexander, MD; Anne-Marie Slinger-Constant, MD

Disclosures

J Child Neurol. 2004;19(10):744-758. 

In This Article

Treatments Involving the Visual System

Stein and Talcott showed that a subset of subjects with dyslexia might have abnormal magnocellular systems, causing decreased visual motion sensitivity, with poor visual guidance of the eye movements that result in inferior binocular vergence control.[47] This problem with vergence control results in difficulty fixating on near targets and might explain why the children reported trouble with letters moving around on the page. This visual motion sensitivity has been found to be a predictor of orthographic skill, accounting for more than 15% of the variance in the reading accuracy of irregular sight words.[54] Stein et al. reported on a large intervention study (two groups of 70 children, average age 8 years, 9 months, of normal intelligence, with reading skills more than 2 SD below the mean).[55] The subjects met the criteria for severe dyslexia and unstable binocular vision and were randomly assigned to wear yellow-tinted glasses with or without occlusion of the left lens (because most of the children were right handed). Yellow tinting was chosen because the magnocellular system, felt to be deficient in these children, gets a boost in the yellow range. Stein et al. reported that short-term monocular occlusion helped the children to overcome their binocular fixation instability, and, while using only one eye to read, visual inconsistency and confusion resolved. The children were seen every 3 months for 9 months and were assessed for binocular stability and reading ability. Both groups began treatment reading at the 6.8- to 6.10-year-old level. At the end of 9 months, the group with monocular occlusion had gained 16.1 months in reading ability but still remained significantly behind (at the 8.1-year-old reading level at the age of 9.5 years). The children who made the greatest gains were those achieving binocular stability. In fact, when a child demonstrated inconsistent stability over time, the reading gains for the 3-month period of instability were 1.2 months per month, in contrast to an average of 2.1 months per month when stability was present. The group with tinted lenses alone manifested only an 8-month gain over the 9-month period. Stein et al. noted that the group treated with tinted glasses alone achieved a greater than expected rate of binocular stability over the 9 months (54%, in contrast to a similar study using clear glasses, with a rate of 20 to 24%). They wondered if this difference could be due to the color giving a boost to the magnocellular system. They noted that most children with dyslexia have a core deficit in the phonologic system of language but proposed that in a subset of subjects with dyslexia, visual processing difficulties might account for orthographic mapping problems owing to the inconsistency of the visual input.

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