The Changes of Corneal Astigmatism and Refraction After Horizontal Rectus Muscle Surgery in Intermittent Exotropia

ABSTRACT

PURPOSE: To investigate changes in corneal astigmatism and refractive power in intermittent exotropia after lateral rectus recession with or without medial rectus resection. METHODS: We compared visual acuity, spherical equivalent, refractive power, astigmatism from cycloplegic refraction, and Orbscan corneal topography in two groups consisting of 40 eyes from 20 patients who underwent bilateral lateral rectus recession (Group 1) and 33 eyes from 33 patients who underwent monocular medial rectus resection with lateral rectus recession (Group 2) immediately preoperatively and at 1 and 4 weeks postoperatively. RESULTS: In Group 1, the refractive power changed +0.12 D on average in the horizontal median and -0.08 D on average in the vertical median at 1 week postoperatively. The refractive power changed +0.07 D on average in the horizontal median and -0.04 D on average in the vertical median at 4 weeks postoperatively. No significant change in the corneal astigmatic axis was detected. In Group 2, the refractive power changed +0.4 D on average in the horizontal median and -0.19D on average in the vertical median, and the corneal astigmatic axis significantly shifted by +0.51 D in the 'with-the-rule astigmatism' direction at 1 week postoperatively (p=0.02). However, the refractive power changed +0.2 D on average in the horizontal median and -0.09 D on average in the vertical median, and the corneal astigmatic axis changed +0.2 D at 4 weeks postoperatively, although these values were not statistically significant. CONCLUSIONS: Postoperative refractive power and corneal astigmatism did not change significantly, as compared to preoperative values, at 4 weeks postoperatively in the lateral rectus recession-only or medial-and-lateral rectus recession group.