Inferior oblique anterior transposition according to a different grading scale for hyperdeviation with inferior oblique overaction.

Objective: To define an inferior oblique anterior transposition (IOAT) grading scale in patients with hyperdeviation and inferior oblique overaction (IOOA), which we planned based on the data we obtained in our previous retrospective study.

Design: Prospective cohort study.

Participants: Thirty-eight patients who underwent graded IOAT.

Methods: The patients were divided into 5 groups according to the amount of hyperdeviation in the primary position (PPHD). The inferior oblique muscle was transposed 2 mm posterior, 1 mm posterior parallel, 1 mm anterior, and 2 mm anterior to the inferior rectus insertion, respectively. Surgical success was defined as success (PPHD ≤3 PD), partial success (PPHD >3 and ≤6 PD), and nonsuccess (PPHD >6 PD).

Results: The mean amount of hyperdeviation correction in groups after IOAT was 9.50 ± 0.9 PD (range, 8-10 PD), 12.43 ± 1.5 PD (range, 11-14 PD), 16.67 ± 1.4 PD (range, 15-18 PD), 19.57 ± 1.7 PD (range, 16-21 PD), and 22.57 ± 5.8 PD (range, 14-30 PD), respectively. Surgical success was achieved in 34 patients (89.5%) after surgery, partial success was achieved in 3 patients (7.9%), and nonsuccess was observed in 1 patient (2.6%). All patients in our study had unilateral IOOA preoperatively, and IOOA developed in the contralateral eye of 9 patients (23.7%) during postoperative follow-up. In group 5, 4 patients (57.1%) developed -2 upgaze limitation, but surgery was not required.

Conclusions: A high success rate can be achieved with this grading of IOAT in primary and secondary IOOA cases accompanying hyperdeviation in the primary position.