Meta-Analysis of Eye Movements Between Children With and Without Dyslexia or Reading Disability

Abstract

Background: Hundreds of studies have compared eye movement variables in subjects with and without dyslexia or reading disability. Most studied only small sample sizes and the eye movement tasks and targets varied. The aims of this study are to determine which, if any, eye movement variable(s) differ between children with and without dyslexia or reading disability, and, if differences are found, quantify the amount. Methods: Search engines PubMed and Salus/EBSCO Discover Database for key words eye movements OR saccades OR fixation AND dyslexia OR reading disability yielded 728 titles. Following initial study eligibility criteria (objective eye movement variable measures of children age 6-15.5 years in defined case and control groups), 43 studies qualified for in depth review. Eleven studies qualified for data synthesis. Data were extracted, tested for normality by Kolmogorov-Smirnov statistic, standardized, weighted by sample size, tested for homogeneity by Q test, pooled and measured for combined effect. Results: Combined relative risk effect revealed fixation duration, number of fixations, and number of regressions when reading words to be 2.33 (95% CI: 2.12-2.54) times longer, 1.58 (95% CI: 1.52-1.65) times higher, and 1.83 (95% CI: 1.68-1.97) times higher respectively in children with dyslexia or reading disability compared to age normal readers. Differences reading pseudowords were not statistically significant. Conclusions: Significant differences in fixation duration, number of fixations, and number of regressions were found during word reading. Because most reading time is during the fixation duration, children with dyslexia or reading disability need, on average, 2.33 times longer. The results provide objective data to support reading time accommodations for Individual Education Plans. Systematic review suggests that oculomotility ability depends on the amount of cognitive processing rather than purely on extra ocular muscle control.