Corneal topographic changes after extraocular muscle surgery

Purpose: Changes in refractive error have been reported after strabismus surgery. The influence of extraocular muscle tension on corneal topography is thought to be an important mechanism contributing to this alteration. This study investigates topographic changes after strabismus surgery in human beings. Methods: The corneal topography of 63 eyes of 43 patients who underwent either strabismus or optic nerve sheath fenestration (ONSF) surgery was measured before and after operation. The ONSF surgery involved removing and reattaching the medial rectus muscle, thus acting as a control for the strabismus procedures. Corneal power was measured centrally and at 1.5 and 3.0 mm in 8 meridians. Analysis of variance was performed to compare the difference in preoperative and postoperative corneal power for all procedures and comparing recessions, resections, combined recession and resection, and ONSF as grouped procedures. Results: All groups showed a significant change in preoperative to postoperative corneal power (P < .01). A significant change was seen between all grouped procedures except when the resection was compared with ONSF and compared with recession. Conclusions: Change in the tension of 1 muscle does not produce a change in the adjacent quadrant as much as it produces a significant change in the entire corneal surface, which illustrates the interaction and interdependence all corneal positions have with respect to each other. (J AAPOS 1999;3:80-6)