Strabismus Surgery Outcomes and Their Determinants in Patients with Chronic Sixth Nerve Palsy

PURPOSE: Patients with chronic sixth nerve palsy (CSNP) comprise a heterogeneous population, and the optimal surgical solution remains uncertain. Here, we present the success rate and factors associated with the success of strabismus surgeries for CSNP. METHODS: This was a retrospective cohort study of patients with strabismus due to CSNP operated on between 2015 and 2019 in a tertiary eye hospital in central Saudi Arabia. Surgical success was defined as a horizontal deviation of ≤10 prism diopters (PDs) assessed at least 12 months after surgery. Differences between groups with respect to the primary outcome were assessed. RESULTS: Fifty-five patients were analyzed with a median follow-up of 24 (range 12–48) months. Superior rectus and inferior rectus transposition (34.5%) and medial rectus recession with lateral rectus resection (32.7%) were the main surgeries performed. The overall success rate was 67.3% (95% confidence interval 54.9–79.7). Bilateral CSNP (P = 0.05), a higher preoperative angle of deviation (P = 0.002), or a greater degree of preoperative limitation of abduction (P = 0.012), but not the type of surgery (P = 0.09), were more likely to result in an under-corrected outcome of >10 PD. The preoperative deviation angle showed a trend toward being associated with a poor outcome after surgery (P = 0.06). Six patients with high-angle deviation before surgery required second surgery. CONCLUSION: While the surgical procedure does not impact outcomes, the severity of preoperative horizontal deviation might impact surgical success and the need for reoperation. Patients with severe CSNP should be counseled appropriately about the chances of surgical success and the potential need for further interventions.