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While the most commonly accepted theory of reading disabilities involves deficits in phonological processing, early and current research in the field suggests that some individuals with reading disabilities may have difficulty with visual processing instead of, or in addition to, difficulties with phonological processing. Individuals with visual processing difficulties may complain of small letters blurring, merging, and moving while they attempt to read; skipping lines and/or losing their places when reading; or discomfort such as headaches and eyestrain after close work. In the field of optometry, these complaints reflect symptoms of oculomotor dysfunction. To investigate the frequency and severity of visual complaints across a continuum of reading ability, a visual complaint scale was designed and administered to 20 college students with and 44 without learning disabilities. To explore the relationship of visual complaints to reading, participants were also assessed on measures of general cognitive functioning, phonological processing skill, visual processing speed, eye movement efficiency, and reading rate and fluency. The relationship among the measures was explored, and all measures were examined in terms of their potential relationship to reading rate and fluency. A reading experience questionnaire was administered to provide a context for interpretation of results.
Results indicate that college adults with diagnosed learning disabilities score significantly lower on measures of visual processing speed (despite ceiling effects) and reading rate, and they report more visual complaints while reading than those not identified with learning disabilities. Groups demonstrate similar levels of performance on measures of eye movement efficiency, phonological processing skill, and reading fluency (although ceiling effects may account for these similarities). All measures are intercorrelated, except the measure of efficiency of saccadic eye movement. Self-reported reading experiences also distinguish group membership. Based on the entire cohort, an estimated 22.3% of the variance in reading rate can be explained by visual processing speed, and an estimated 30.4% of the variance in reading fluency can be predicted by visual processing speed and general cognitive functioning. The results of the study support the continued investigation of the role of visual processing in reading difficulties and the further development of the visual complaint scale.