Saccadic eye movements are impaired in Duchenne muscular dystrophy

Extraocular muscles are generally considered to be spared in Duchenne Muscular Dystrophy (DMD). However, this assumption is based mainly on clinical observations, as systematic eye movement recordings have been performed in a very limited number of cases. Our goal was to analyze several saccade parameters in a higher number of cases, in order to reveal a possible ocular-motor impairment in DMD. Data were collected from a population of 9 subjects with DMD and 9 healthy male subjects of comparable age as controls. We used the electrooculographic (EOG) technique coupled with advanced digital signal processing; saccade duration, amplitude, mean velocity, peak velocity and K factor (ratio mean/peak velocity) were measured. The DMD group showed saccades with significantly longer duration and lower velocity, with respect to controls; these differences were accounted for mainly by the largest movements, whereas there were no significant differences at the smallest eccentricity tested (3 deg). Neither amplitude nor K factor were significantly different from controls for any of the eccentricities tested. To our knowledge. this is the first study to suggest significant impairment of eye movements in Duchenne muscular dystrophy.