Effects of vertical offsets of the horizontal rectus muscles in V-pattern exotropia without oblique dysfunction.

PURPOSE: To investigate the effects of vertical offsets of the horizontal rectus muscle in V-pattern exotropia without oblique dysfunction. METHODS: A computerized patient database was searched for patients treated with full tendon offsets for V-pattern strabismus from 2002 to 2007. Patients with clinically significant inferior oblique overaction were excluded. Surgery included upward transposition of lateral rectus muscles and/or downward transposition of medial rectus muscles. Medical records were retrospectively analyzed for alignment in the primary position, 30 degrees upgaze, and 30 degrees downgaze before and 3 months after surgery. The main outcome measure was the change in V pattern after surgery. RESULTS: The search identified 11 patients who met inclusion criteria. Of these, 6 underwent bilateral lateral rectus recessions, 1 had 3-muscle surgery, and 4 had monocular recession-resection surgery. The preoperative V-pattern (horizontal) deviation between upgaze and downgaze was 22.2(Delta)+/-5.0(Delta). Postoperative deviation at 3 months was 3.5(Delta)+/-3.9(Delta), a decrease of 18.9(Delta)+/-7.5(Delta). Postoperatively, no patient had an A-pattern deviation or subjective torsional disturbance. The amount of V-pattern correction was closely correlated with the size of the preoperative V pattern (r=0.84). CONCLUSIONS: In patients with V-pattern exotropia without inferior oblique dysfunction, vertical offsets of the horizontal rectus muscles effectively corrected the pattern deviation. The amount of correction was closely correlated with the size of the preoperative V pattern.