Refractive effect of the horizontal rectus muscle recession

Purpose To determine refractive and corneal topographic changes after horizontal rectus muscles recession. Methods In a noncomparative interventional case series, 49 eyes of 27 patients were evaluated in two groups: (1) exotropic patients (24 eyes) who underwent lateral rectus muscle(s) recession, and (2) esotropic patients (25 eyes) who underwent medial rectus muscle(s) recession. Full ophthalmic examination including cycloplegic automated refraction was carried out before, 1 and 3 months after surgery. Corneal topography was performed preoperatively and repeated at 3 months postoperatively. Results In eyes underwent medial rectus recession, there were statistically significant myopic shifts in spherical equivalent at month 1 (from + 2.09 ± 1.82 to + 1.88 ± 1.83 diopters, P = 0.03) and in astigmatic power at both month 1 (from −0.85 ± 0.67 to −1.15 ± 0.65 diopter, P = 0.04) and month 3 (from −0.85 ± 0.67 to −1.16 ± 0.65 diopter, P = 0.01). Myopic shifts were also noted following lateral rectus recession; however, there were not statistically meaningful. Significant astigmatic axis shift, which was toward with the rule astigmatism, was detected only after lateral rectus recession at both month 1 (P = 0.02) and month 3 (P = 0.02). Corneal power measured by topography was also demonstrated a statistically significant reduction (less than 0.3 diopter) after recession of either medial (P < 0.001) or lateral (P < 0.001) rectus muscle. Conclusions In spite of being statistically significant in some parts, the amounts of refractive and corneal topographic changes were not clinically remarkable. Therefore, it does not seem necessary to perform cycloplegic refraction early after horizontal rectus muscle recession; however, a precise refraction in all cases of strabismus should not be deferred later than 3 months.