Ipsilateral gaze deviation as a risk factor for surgical overcorrection in two-muscle surgery for unilateral superior oblique palsy.

Purpose: To investigate the angle of deviation in various gaze positions as a risk factor for overcorrection of moderate-angle unilateral trochlear nerve palsies treated with two-muscle surgery.

Methods: The medical records of consecutive patients with presumed unilateral moderate-angle trochlear nerve palsy who underwent two-muscle surgery were retrospectively reviewed. Patients with overcorrection, defined as reversal of hyperdeviation by prism alternate cover testing at distance (straight ahead) or near measured at 6 weeks, were compared to non-overcorrected patients for their preoperative torsion and ocular alignment at near and distance.

Results: A total of 45 patients (age range, 12-77 years; 24 [53%] males) with deviation ranging from 14 to 25 in primary position underwent two-muscle surgery, of whom 8 (18%) experienced surgical overcorrection by 6 weeks' follow-up. The preoperative angle of deviation was similar between overcorrected and non-overcorrected patients for eight of nine cardinal distance positions and near gaze; however, patients with smaller deviations in ipsilateral gaze were more likely to be overcorrected with two-muscle surgery (8.5 vs 16.0 [P = 0.029]). Cut point analysis determined that an ipsilateral gaze of ≤9 was significantly associated with overcorrection. Greater lateral incomitance also trended toward overcorrection (15.0 vs 9.0 [P = 0.059]). Torsion was not a clinically significant indicator of overcorrection (3.5 vs 6 [P = 0.083]).

Conclusions: A preoperative ipsilateral angle of ≤9 was associated with overcorrection in patients undergoing two-muscle surgery for moderate angle unilateral trochlear nerve palsies.