Significant correlation found between visual deficits, dyslexia
Deficits in visual functioning are more prevalent in children affected by developmental dyslexia, according to a group comparison observational study conducted on 62 children with a mean age of 9 to 10 years.
Patients for the trial were divided in two groups. Twenty-nine children who received a diagnosis of developmental dyslexia (DD) were recruited from a hospital-based clinic, while a control group of 33 typically developing (TD) readers were recruited from patients of the same age who received standard eye examinations in the same hospital.
Participants underwent psychoeducational testing, comprehensive eye examination and visual function measures. Psychoeducational testing included measurement of IQ and single-word reading and spelling. Vision testing included a standard eye examination with detailed assessment of vergence, accommodation and ocular motion tracking using the Developmental Eye Movement test (DEM) and the Visagraph (Reading Plus) infrared eye tracking test during reading activities.
Median cycloplegic refractive error and eye alignment did not differ between the DD and the TD group. Individual vergence, analyzed with a convergence test and near fusional convergence ranges, demonstrated a significant difference between the two groups, with reduced results for the DD group.
Accomodation deficiency was higher in the DD group. Patients in the DD group performed poorly in the error and horizontal DEM, with a failure range of 45% compared to the 3% of the TD group. In the Visagraph test they performed more poorly than the TD group on all parameters, with a greater proportion of impairments in the DD group.
Findings suggest that visual function deficits are far more prevalent in school-age children with developmental dyslexia than in typically developing children. Despite this correlation, the contribution of visual deficits in developmental dyslexia is still uncertain and will require further studies.
“Although this comparative study does not address any causal association of these deficits with reading performance, the findings support further investigation of visual function in dyslexia,” the authors wrote. – by Michela Cimberle
Disclosure: The authors reported no relevant financial disclosure.