Effect of inferior oblique anterior transposition on vertical deviation.

Purpose: To evaluate the efficacy and complications of simplified graded inferior oblique anterior transposition (IOAT) in treating at least 10 PD vertical deviation in the primary position and inferior oblique muscle overaction (IOOA).

Methods: This retrospective study reviewed the medical records of 65 patients treated with simplified graded IOAT procedures for both vertical deviation and IOOA. Patients were grouped according to vertical deviation in the primary position. Group 1: vertical deviation of not > 20 PD; the inferior oblique (IO) muscle was fixed 2 mm posterior and 2 mm temporal to the inferior rectus insertion. Group 2: vertical deviation > 20 PD; the muscle was fixed at the level of insertion of the inferior rectus muscle. Postoperative outcomes in vertical deviation (≤ 5 PD, excellent; 5-10 PD, fair; > 10 PD, poor), IOOA, anti-elevation syndrome (AES), abnormal head position (AHP), V-pattern, and foveal disc angle (FDA) were assessed.

Results: Patients were categorized as 43 (53.5% men) in group 1 and 22 (54.5% men) in group 2. IOAT improved vertical deviation, IO muscle function, AHP, V-pattern, and FDA. IOOA decreased from + 2.1 to 0.02 in group 1 and from + 2.4 to 0 in group 2. Mean vertical reduction after IOAT was 12.4 ± 3.8 and 23.8 ± 7.3 PD in groups 1 and 2, respectively. Excellent results were achieved in 83.7% and 77.3% of patients and fair results in 16.2% and 18.2%, respectively. Among the 48 asymmetric DVD patients, 83.8% and 82.3% in groups 1 and 2, respectively, achieved satisfactory results. No AES occurred in two groups.

Conclusion: The simplified graded IOAT procedure, which is graded only on the basis of vertical deviation, can achieve satisfactory results for resolving IOOA with vertical deviation or DVD, AHP, V-pattern, and FDA. In addition, the modified procedure of fixing posterior fibers at a slight posterior tilt is clinically instructive in correcting vertical deviation > 20 PD while reducing AES complications.