Objective: To identify factors predictive of operative success or failure for vertical muscle surgery performed in patients with Graves' ophthalmopathy.
Design: Prospective noncomparative case series.
Participants: Thirty-one consecutive patients with Graves' ophthalmopathy who demonstrated vertical ocular motor imbalance, with or without simultaneous horizontal muscle imbalance.
Intervention: Vertical extraocular muscle surgery performed either in isolation or in association with horizontal muscle surgery.
Main outcome measurements: Vertical limitations of extraocular muscles were correlated with preoperative hypertropia. Stepwise linear regression was used to determine the significant predictors of postoperative hypertropia in primary gaze. Logistic analysis was used to estimate the probability of surgical failure (>5 diopters) on the basis of preoperative parameters.
Results: The amount of preoperative hypertropia was negatively correlated with total restriction of vertical ductions (r = -0.52, P < 0.01). Preoperative hypertropia was positively correlated with asymmetry in muscle restriction between the two eyes (r = 0.67, P < 0.0001). The best predictor of preoperative hypertropia was the difference between restriction of the contralateral opposing recti, namely the right superior rectus, and the left inferior rectus, as well as the right inferior rectus and the left superior rectus (r = 0.74, P < 0.0001). Restriction of the contralateral opposing recti was also the most significant predictor of surgical success (postoperative hypertropia < 5 prism diopters).
Conclusions: Surgery tailored to address restriction of ductions, specifically the difference between contralateral opposing recti, is likely to improve the success of initial surgery beyond that based primarily on the magnitude of the vertical deviation.