Effect of combining oblique muscle weakening procedures with bimedial rectus recessions on the surgical correction of esotropia

PURPOSE To evaluate the effects of oblique muscle weakening when combined with medial rectus muscle recession on the primary position horizontal alignment after surgery to correct esotropia. METHODS The medical records of patients who underwent bilateral medial rectus recessions with or without simultaneous oblique muscle surgery between 2004 and 2013 at two Brazilian hospitals were retrospectively reviewed. Patients who had undergone previous strabismus surgery and those with incomplete data were excluded. The amount of correction for every millimeter of medial rectus recession was analyzed for patients undergoing an isolated procedure (group A), those undergoing additional inferior oblique muscle weakening (group B), and those undergoing additional superior oblique muscle weakening, or tenectomy (group C). RESULTS A total of 160 patients (71 females) met inclusion criteria. The magnitudes of preoperative esotropia and the times of postoperative evaluation did not differ between groups. The amounts of correction did not differ when patients younger and older than 7 years were compared in every group. The amounts of correction for every millimeter of medial rectus recession were 3.0(Delta) in group A, 3.1(Delta) in group B, and 2.6(Delta) in group C. The reduction for group C was significant (P = 0.0036). CONCLUSIONS Pateints undergoing superior oblique weakening surgery in combination with bimedial rectus recessions may require larger medial rectus recessions to correct the primary position esodeviation. The authors suggest that a 10%-15% increase of the planned recession should be considered.