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Kathryn Hannis, Sowjanya Gowrisankaran, Emily A Swanson, Deborah Waber, Aparna Raghuram; Oculomotor tracking deficits in children with dyslexia. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5428.
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© ARVO (1962-2015); The Authors (2016-present)
Dyslexia is a neurodevelopmental disorder whose hallmarks are unusual difficulties in word recognition, spelling and decoding in the context of normal intelligence and access to standard reading instruction. The research literature implicates multifactorial deficits not limited to the linguistic brain, including disordered eye movements during reading. The aim of our study was to assess the efficacy of the Developmental Eye Movement (DEM) test – a quick clinical tool and Visagraph (VIS) – a low cost eye tracker in evaluating oculomotor (OM) deficits in children with dyslexia.
A prospective observational study was carried out involving 30 typically reading and 29 children with dyslexia (7- 11 yrs). Eye movements during reading were recorded using the VIS, an infrared, limbal-reflection recording system. Reading rate (RR), number of fixations (FIX) and regressions (REG) were analyzed. For the VIS, all participants were tested using reading material at their current reading proficiency grade level, established by pretesting with the Woodcock Reading Mastery Word Identification test. The DEM test is a visual-verbal ocular motor assessment tool that provides four index scores – vertical time (V), adjusted horizontal time (H), errors and ratio.
When reading text at reading proficiency grade level, the dyslexic group had significantly slower RR (Mean±SE of 110.78±7.28; 194.20±12.4), as well as more FIX’s (199.26±13.97; 134.06±7.32) and REG’s (44.56±5.65; 23.47±1.62) relative to the control group (all p=0.01). Between-group differences in the errors (9.79 ±2.04; 2.25±0.79) from the DEM was also statistically significant (p =0.01). There was a significant correlation between the H, V, and errors from the DEM with RR (p=0.05). H, and V from the DEM were correlated with number FIX’s (p=0.01). Performance of a subset of the dyslexic group on texts at one grade below estimated reading proficiency (n=11), did not differ from performance at their grade level of proficiency by paired T-test analysis for RR, FIX or REG (p>0.05).
Tracking deficits are common in children with dyslexia and these deficits may persist even when reading texts at and below their grade level of reading proficiency. The DEM test may be a valid rapid screening tool to identify potential OM tracking deficits in patients with dyslexia.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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