Changes in Corneal Topography and Clinical Refraction Following Horizontal Rectus Muscle Surgery

Abstract

Objectives. Refractive changes have been studied after muscle surgery in literature but most results are inconsistent.It has been postulated that changes in corneal tension after muscle surgery may cause a change in corneal curvatureresulting in the change in refraction postoperatively. This study investigated changes in corneal topography andclinical refraction after horizontal rectus muscle surgery.
 Methods. Twenty-one eyes of 13 patients underwent horizontal rectus muscle surgery via limbal approach. Manifestrefraction, cycloplegic refraction, and corneal topography were measured preoperatively, and postoperatively at day 1and weeks 1, 2, 4 and 8. The proportion of subjects with at least 0.5 D change from preoperative measurements and the proportion of subjects that needed new prescription postoperative were also computed. Analysis of the results were done using the Friedman test to identify significant differences among measurements at different time periods with post-hoc analysis utilized to identify specific time periods with significant changes from preoperative measurements.
 Results. Mean corneal keratometry, horizontal, vertical, and oblique astigmatism, obtained topographically showed nosignificant difference from preoperative measurements. The statistically significant difference in corneal astigmatismin the recession group at day 1, week 4 and week 8 postoperatively was not confirmed when converted to powervectors in both vertical/horizontal (J0) and oblique (J45) astigmatism. Clinical refraction showed a transient myopicshift in spherical equivalent, statistically significant only on postoperative day 1 in the recession group. There was nostatistically significant difference in clinical astigmatism. There was ≥ 0.5 D change in spherical equivalent in 60% inboth study groups by the end of follow-up. The shift in J0 was more than 10% in the recession group. More than fiftypercent (52.4%) needed new prescription for glasses.
 Conclusion. No statistically significant change in corneal topography and clinical refraction following horizontal rectusmuscle surgery were found. Patients should still be refracted at least 2 weeks postoperatively to check if there is aneed for change in prescription glasses to improve alignment and/or improve vision.