The effect of inferior oblique weakening on vertical deviation in contralateral gaze

To quantify the effect of isolated, unilateral inferior oblique (IO) weakening procedures on reducing the preoperative contralateral vertical deviation.

We performed a retrospective cohort study of 59 patients who underwent unilateral IO weakening. Postoperative vertical deviation was modeled with analysis of covariance, with surgical technique as a fixed factor and baseline vertical deviation, age, and weeks since surgery as covariates. Primary outcomes were adjusted postoperative contralateral deviations in elevation, horizontal gaze, and depression; secondary outcomes, ipsilateral deviations.

Mean patient age was 42.2 ± 21.1 years. Superior oblique palsy was the most common indication for surgery (48%). Mean baseline contralateral vertical deviations were approximately 17^Δ-18^Δ across contralateral elevation, horizontal gaze, and depression. Mean follow-up was 2.7 months, with estimated marginal means corresponding to approximately 11-14 weeks. Adjusted postoperative contralateral deviations were 6.48^Δ (95% CI, 4.49-8.48) in elevation, 7.20^Δ (95% CI, 5.16-9.23) in horizontal gaze, and 5.96^Δ (95% CI, 3.73-8.19) in depression, representing descriptive reductions of approximately 10^Δ-12^Δ. Ipsilateral adjusted residual deviations were 5.86^Δ, 5.80^Δ, and 5.50^Δ for elevation, horizontal gaze and depression, respectively. Baseline deviation was the dominant predictor of outcome (partial η² up to 0.77), whereas follow-up time and age were not associated with postoperative deviation.

In our small study cohort, isolated unilateral IO weakening resulted in moderate early reductions in contralateral vertical deviation across elevation, horizontal gaze, and depression, with smaller ipsilateral changes.