Abstract
Purpose: :
A number of authors have hypothesized a relationship between cerebellar functioning and autism. Some studies have shown correlated changes in oculomotor behavior. This study compares the conjugate eye movements of children with autism spectrum disorder with those of normal age-matched controls.
Methods: :
Children with autism spectrum disorder (ASD, n=13) and typical age matched control children (TYP, n=23) were tested on a range of eye movement tasks at Seattle Children’s Hospital. The average age of the subjects was 10.4 y. Subjects were assessed while holding gaze in the dark, fixating stationary point targets at different eccentricities, making saccades to pseuorandomly presented point targets, making sequential saccades to stationary targets in a patterned array, making anti-saccades, pursuing a sinusiodally moving point target, viewing a moving high-contrast full field grating (OKN), and during en-block rotation about a fixed vertical axis in the dark (VOR). Eye movements were recorded binocularly with an SMI videonystagmography system. All subjects were given the same instruction.
Results: :
With three notable exceptions, ASD children had stable gaze holding in the dark and during fixation of eccentric targets. Saccades to stepped targets were highly variable in a subset of the ASD children, with many showing hypometric saccades of long duration. Smooth pursuit was variable overall, but ASD children on average had remarkably good pursuit performance. OKN was abnormal in ASD children only at higher target velocities. VOR had normal gain in most ASD children. The most dramatic differences were seen in the sequential saccade task and the antisaccade task. Children with ASD had consistently poorer performance than TYP children, despite demonstrating a clear understanding of the task.
Conclusions: :
Taken together these results show clear differences between ASD and TYP oculomotor performance in children. However, the remarkably well-preserved smooth pursuit performance is not entirely consistent with cerebellar models of ASD.
Keywords: eye movements: conjugate • eye movements: saccades and pursuits • eye movements