Changes in the axis of astigmatism and in fundus torsion following inferior oblique muscle weakening

Abstract

To study the changes in fundus torsion and in the axis of astigmatism following inferior oblique (IO) myectomy in patients with inferior oblique overaction (IOOA). The degree of fundus torsion and corneal astigmatism were prospectively evaluated before and 3months after IO myectomy in patients with IOOA grade +2 or more in one or both eyes and an astigmatic error of ≥1 D. Fundus torsion was evaluated by measuring the disk foveal angle (DFA) using fundus photography. The axis of astigmatism was identified from the anterior sagittal map using Pentacam corneal imaging. A total of 54 eyes of 27 patients were included. Patients were divided into two groups: those with esotropia and those with exotropia. All patients had a preoperative DFA >8°, which decreased postoperatively in both groups (P<0.01). Postoperatively, there was incyclorotation of the axis of astigmatism by >5° in 80% of the esotropic group and 75% of the exotropic groups (P<0.01). Incyclorotation of the axis of astigmatism occurs after IO myectomy. Measurement of the change in the axis of astigmatism can be used to assess the torsional changes after IO myectomy in patients with IOOA.