Regulation of static and dynamic ocular alignment in patients with trochlear nerve pareses.

Ocular alignment and saccades were studied in seven patients with trochlear nerve pareses, before and after strabismus surgery. Prior to surgery, a position-dependent vertical ocular misalignment was present, and downward saccades were hypometric in the paretic eye. Strabismus surgery reduced the magnitude and position-dependence of the static misalignment. Saccade conjugacy improved in the patients with congenital pareses, and in the patient with a gradual-onset acquired paresis, but less improvement occurred in subjects with traumatic pareses. The post-operative change in saccade conjugacy relative to the change in static alignment correlated with pre-operative vertical vergence, suggesting that changes in saccade yoking depend on an interaction between saccades and vertical vergence.