Stability of the postoperative alignment in adjustable-suture strabismus surgery.

We reviewed the postoperative alignment drift in 201 patients between the ages of 14 and 75 years who underwent rectus muscle surgery with adjustable sutures from 1984 to 1989. We analyzed results for 42 primary esotropia (ET) surgeries and 37 reoperations (groups IA and IB, respectively), 34 exotropia (XT) primary surgeries and 66 reoperations (groups IIA and IIB, respectively), and 22 hypertropia (HT) surgeries (group III). Forty percent of patients required postoperative muscle adjustment. All patients underwent a minimum of 8-weeks follow up; 66% underwent 6-months follow up or longer. The postoperative drifts in alignment for primary surgeries versus reoperations were not significantly different for either ET or XT patients. The mean postoperative drift in prism diopters from the alignment immediately after the adjustment, or after the surgery if no adjustment was needed, for each group as measured during the most recent follow up was 1.3 eso-shift for group IA, 1.2 exo-shift for group IB, 4.8 exo-shift for group IIA, 4.1 exo-shift for group IIB, and 1.5 hyper-shift for group III. Only for groups IIA and IIB were these drifts found to differ significantly from zero. Based on these drift patterns, we align ET patients to orthotropia, XT patients to 5 to 7 delta esotropic, and HT patients to 1 to 2 delta hypotropic positions.