Reading Between the Lines

Developmental dyslexia (DD) is a common learning disability, estimated to affect between 5 and 10 percent of the US population (1). Although researchers agree on its origins, there are still facets of the disorder that are not fully understood – including whether visual processing deficits are more prevalent in children with DD. Now, an observational study involving 29 school-aged children with DD and 33 typically-developing (TD) children has attempt to provide an answer (2).

“We set out to initially determine whether visual function deficits are in fact more prevalent in children with developmental dyslexia”, says Aparna Raghuram, who led the study. “Establishing that such differences exist would be essential as a basis for any further studies to evaluate whether treating vision makes sense.”

Participants spent two hours undergoing psychoeducational testing, comprehensive eye examinations, and visual function measures – assessing vergence, accommodation, and ocular motor tracking. Ocular motor tracking was evaluated two ways – with a printed test and infrared eye tracking – and all parametric analyses for the vision measures were adjusted for age and sex. 

Children with DD exhibited more deficits in peripheral visual function – specifically vergence, accommodation, and/or ocular motor tracking – than the non-randomized group of TD children: 23 children (79 percent) in the DD group had deficits in one or more domain of visual function, compared with 11 children (33 percent) in the TD group (p<0.001).

“This study provides evidence that visual function deficits are prevalent in children with developmental dyslexia” says Raghuram. “Hence, it would be premature for clinicians and educators to discount a potential role for visual function in some children with developmental dyslexia until more is known. By the same token, however, our findings do not establish that visual deficits are the primary cause of dyslexia, even if visual deficits play a role.”