Background: Changes in refraction follow surgery on the extraocular muscles. We examined corneal topography before and after medial or lateral rectus muscle recession using a computer-assisted topographic analysis system. Methods: A total of 36 patients (52 eyes) were examined. Measurements were taken 1 day before surgery and 1, 15, and 30 days after surgery. Results: A significant change in astigmatic power was detected 1 day after surgery in the meridian of the recessed muscle, evidencing a localized flattening of the cornea. Induced astigmatism decreased over time. At 30 days following surgery, 6% of patients evidenced a residual change higher than 1 diopter (D); 12% evidenced a residual change higher than 0.5 D. Conclusion: The increase of astigmatic power recorded 1 day after surgery is higher for medial rectus muscle recession than for lateral rectus muscle recession. Corneal topography changes, located mainly in the meridian of the recessed muscle and the optical zone, are greatly reduced or gone within 1 month of surgery.