This is a cross-sectional study of children (<17-years-old) with a glaucoma drainage device (GDD) (Ahmed vs Baerveldt) implanted consecutively by a single surgeon from the Toronto group, between September 2006 and May 2018 and who had an ocular motility examination between May 2017 and December 2018. There were 21 eyes in the Ahmed group (AG) and nine in the Baerveldt group (BG), the mean follow-up time between GDD insertion and motility examination was 68 months in the AG and 19 months in the BG. Thirty-three percent had a moderate to severe limitation of dextroelevation, 30% in laevoelevation, 10% in abduction and adduction. Forty-six percent had exotropia and 46% had vertical heterotropia post-GDD insertion. Sixty-two percent in the AG had at least a moderate (>-2) restriction in motility compared to 22% in the BG. The authors postulated that the most likely causes of the restrictive problems are due to the mechanical limitations or the mass effect of the plate and bleb formation. In addition, the disparity in the follow-up period between the AG and BG, and factors related to a longer period post-surgery, of more extensive fibrosis in the plate area, greater thickening of the Tenon’s capsule overlying the bleb and the spread of comitance with secondary contracture of the ipsilateral antagonist muscles in the eyes in the AG cannot be excluded since none of these patients had forced duction test under general anaesthetics examination.