Magnocellular visual function in developmental dyslexia: deficit in frequency-doubling perimetry and ocular motor skills

Abstract

Purpose: This study aimed to verify if patients with developmental dyslexia present deficits coherent with visual magnocellular dysfunction. Methods: Participants with confirmed diagnosis of developmental dyslexia (n=62; age range=8-25 years; mean age=13.8 years, standard deviation= 3.9; 77% male) were compared to a control group with normal development, matched for age, sex, ocular dominance, visual acuity, and text comprehension. The frequency-doubling technology perimetry was used to evaluate the peripheral Eye-Movement Recording System was used to evaluate ocular motor skills during text reading. Results: The developmental dyslexia group had significantly worse contrast sensitivity in the frequency-doubling technology, with strong effect size, than the matched control group. The developmental dyslexia group had more eyes classified in the impaired range of sensitivity threshold to detect frequency-doubling illusion than the control group. Moreover, the developmental dyslexia group had poorer ocular motor skills and reading performance, revealed by a difference in ocular fixations, regressions, span recognition, reading rate, and relative efficiency between groups. A significant correlation was found between contrast sensitivity and ocular motor skills. good relative efficiency had significantly better contrast sensitivity than participants with poor relative efficiency. Conclusions: The developmental dyslexia group presented a markedly worse performance in visual variables related to visual magnocellular function (i.e., frequency-doubling technology perimetry and ocular motor skills) compared with the importance of evaluating vision of individuals with assessments instruments to evaluate temporal processing, with contrast sensitivity threshold.