Bilateral vertical retraction syndrome in horizontal bilateral Duane's syndrome.

In the cases of vertical retraction syndromes previously reported in the literature, the "leash effect" of vertical recti was responsible for a limitation of motility and for retraction in up- or down-gaze. This vertical retraction syndrome mimics Duane's syndrome and benefits from recession of the taut vertical recti. In the case reported, another mechanism had led to vertical retraction syndrome. In a bilateral horizontal Duane's syndrome, the physiological co-contraction of abnormally short horizontal recti in vertical gaze was responsible for vertical retraction syndrome and even for a positive vertical forced duction test. The vertical motility was returned to normal by recession of the four horizontal recti.