A study published in the journal JAMA Ophthalmology 2018 set out the assess the frequency of visual deficits in children with developmental dyslexia (DD). They were not looking to see if the children could see 20/20. They were looking for binocular vision problems such as vergence, accommodation and ocular motor skills. The researchers measured the visual functions that we typically measure in a comprehensive eye exam, especially where a patient wants to be assessed for vision therapy:
deficits in vergence (amplitude, fusional ranges, and facility), accommodation (amplitude, facility, and accuracy), and ocular motor tracking (Developmental Eye Movement test and Visagraph eye tracker). These visual functions can be categorized as binocular vision functions.
The researchers found that 79% of children in the DD group had binocular vision problems compared to 33% for the control group. These are not problems that can be corrected with glasses or contact lenses. They are problems what can respond to vision therapy.
The significance of the study was that the researchers concluded that visual function deficits contribute to the problems that children with DD experience in acquiring reading skills. Our take on the results is that children with a DD diagnosis would benefit form a complete binocular vision examination and, if needed, vision therapy, to ensure that that visual functioning is not an obstacle to their reading ability.