Early on, dyslexia and other reading challenges were believed to be caused by visual deficits. The belief was that struggling readers were unable to visually process what they were seeing and that that interfered with their reading fluency and comprehension. To combat this, opticians began offering “vision therapy,” an intervention aimed at correcting visual deficiencies and strengthening optical function. While uncorrected visual impairments (such as myopia, or “near-sightedness”) can interfere with reading and academic performance in general, they are not the cause of dyslexia. As such, vision therapy has not been proven as an effective intervention for dyslexia.
Instead, dyslexia is a disorder of phonological processing, meaning it relates to sounds and language rather than the visual component of reading. Brain imaging studies have found differences in left hemisphere activation, which is the area of the brain responsible for language, as well as auditory processing. Multiple regions in the brain show differences between those with and without dyslexia. While there are some differences in the occipital (or vision center) area, these are just one of many regions involved.
Given the importance of phonological awareness in reading development, interventions for dyslexia typically involve increasing a child’s knowledge of letter sounds, how those sounds blend to become words, and how those sounds are represented by letters. Reading fluency, building vocabulary, and increasing comprehension are also components of reading intervention. Each of these areas is heavily focused on auditory processing and language development, and reading interventions that do not include these components (such as vision therapy) are not likely to be sufficiently successful.