Purpose: Monocular transposition of the inferior oblique muscle belly (IOMBT) effectively weakened mild to moderate inferior oblique overaction and corrected small primary position hypertropia. Now we aim to evaluate the efficacy of inferior oblique muscle belly transposition (IOMBT) in treating V pattern strabismus with upshoot in adduction.Methods: This is a retrospective review of 13 patients with V pattern who underwent IOMBT procedure from January 2017 to December 2018. The inclusion criteria were: the amount of V pattern from 15 to 25 pd; the degree of upshoot in adduction from +1 to +3; no or trace vertical deviation in primary gaze position. Bilateral IOMBT was performed to reduce the V pattern. Horizontal rectus muscle surgery was performed at the same stage to correct the horizontal deviation. The angle of deviation in upgaze and downgaze was measured pre- and postoperatively. The degree of elevation in adduction was graded. The amount of V pattern was the difference in horizontal angle between up- and downgaze. The change in the amount of V pattern was assessed postoperatively.Results: All 13 patients had complete resolution of the V pattern. The amount of V pattern changed from 18.92 ± 4.310 prism diopters to 3.462 ± 1.854 prism diopters postoperatively. The mean grade of upshoot in adduction changed from 1.92 to 0.12 postoperatively. No depression in adduction or consecutive A pattern were found after surgery.Conclusions: IOMBT can successfully eliminate the V pattern in patients with mild V pattern esotropia or exotropia with mild to moderate upshoot in adduction. This procedure appears to be a useful addition to our inferior oblique surgical armamentarium.
Keywords: Superior oblique palsy; V pattern strabismus; inferior oblique belly transposition (IOMBT); inferior oblique overaction.