The effect of oblique muscle surgery on the axis of astigmatism.

A series of 22 highly astigmatic eyes in 14 patients underwent surgery, either in the form of recessing the inferior oblique, tenotomizing the superior oblique, or tightening the superior oblique. The refractive errors obtained in a masked manner six months postoperative were compared to those preoperative. Weakening the inferior oblique or tightening the superior oblique produced a long-term incyclorotation (clockwise for right eyes and counterclockwise for left eyes) of the axis of astigmatism of approximately 10 degrees. Tenotomizing the superior oblique produced a long-term excyclorotation (counterclockwise for right eyes and clockwise for left eyes) of the axis of astigmatism of about 10 degrees.