Outcomes of anterior nasal transposition in inferior oblique overaction grades +3 and +4: a randomized controlled trial

Background The optimal surgical approach for high-grade inferior oblique muscle overaction (IOOA) remains controversial. Both anterior nasal transposition (ANT) and conventional anterior transposition (ATIO) are used to correct this condition. We aimed to compare the efficacy, postoperative stability, and safety of ANT with ATIO for the treatment of high-grade IOOA.Methods This is a randomized controlled trial on patients with high-grade (+3 or +4) IOOA who were randomly assigned to either the ANT or ATIO group. Primary outcomes included changes in vertical deviation and postoperative grade of IOOA. Secondary outcomes included V-pattern correction, torsional changes, surgical success at 6 months, and postoperative complications.Results A total of 30 patients were enrolled and equally allocated to the two groups. Both groups were demographically and preoperatively comparable. The ANT group demonstrated a significantly greater reduction in postoperative hypertropia compared to the ATIO group that remained stable throughout the follow-up period at 1 week (8.4 ± 3.2 vs. 6.8 ± 2.9Δ, p = .042), 1 month (7.6 ± 3.5 vs. 5.2 ± 2.7Δ, p = .008), 3 months (7.3 ± 3.7 vs. 4.9 ± 2.8Δ, p = .003), and 6 months (7.2 ± 3.8 vs. 4.1 ± 2.9Δ, p = .001). Both procedures were highly effective in correcting IOOA, with no significant difference in the final IOOA grade between the two groups. The complication rates were similar for both procedures with no statistically significant differences.Conclusion Both ATIO and ANT are effective for the management of high-grade IOOA (grades +3 and +4). However, ANT may provide a greater reduction in postoperative hypertropia without increasing complication rates.