Visual Function in Congenital and Childhood Myotonic Dystrophy Type 1

Objective: To investigate visual function in a group of individuals with congenital and childhood myotonic dystrophy type 1 (DM1), to correlate the results to the size of the cytosine-thymine- guanine (CTG) repeat expansion and the onset form, and to compare the results with those of a control group. Design: Cross-sectional study with age- and gender-matched control groups. Participants and Controls: Forty-nine individuals with severe and mild congenital and childhood DM1 and controls matched for age and gender. Methods: The ophthalmologic examination included best-corrected visual acuity (BCVA), refraction, slit-lamp biomicroscopy, indirect ophthalmoscopy, and flash visual evoked potentials (VEPs). Main Outcome Measures: Visual acuity, refractive error, pathology of lens, fundus, and VEP pathologic features. Results: The study shows a higher prevalence of low visual acuity, hyperopia, and astigmatism in the study population compared with the controls. The size of the CTG repeat expansion had an impact on BCVA in all subgroups with lower values in individuals with larger expansion size. In childhood DM1, individuals with high hyperopia and astigmatism had greater CTG repeat expansion size than those without. No true cataract was found. Subtle nonspecific fundus changes were present in addition to VEP pathology. Conclusions: Children and adolescents with DM1 have a variety of visual function pathologies, and DM1 has an impact on the developing visual system, necessitating early ophthalmologic assessment and follow-up.