Drift of ocular alignment following strabismus surgery. Part 1: using fixed scleral sutures.

AIMS: To evaluate the postoperative alignment drift following traditional strabismus surgery utilizing direct attachment of muscle to sclera.
METHODS: The ocular alignment drift (change from the first postoperative week) of 106 patients who underwent scleral fixation strabismus surgery at age 0.5 to 35 years with 5 years' maximal follow-up was analysed.
RESULTS: There was a mean undercorrection drift of 4.6 (SD 8.9) prism dioptres (PD) at distance fixation (p = 0.025) and 3.4 (7.6) PD at near (p = 0.053) for all subjects, and 11.3 (8.6) PD distance (p = 0.008) and 10.6 (6.0) PD near (p = 0.016) for exotropic patients. Recession surgery produced an undercorrection drift of 5.3 (8.8) PD (p = 0.021) at distance fixation. Esotropic patients and those undergoing unilateral recession/resection surgery had no significant drift. Patients overcorrected at the 1-week postoperative visit later developed an undercorrection drift at distance (10.3 (7.9) PD, p = 0.002) and near fixation (5.5 (9.2) PD at 36 months, p = 0.041), while undercorrected patients showed no significant drift and largely stayed undercorrected.
CONCLUSION: Fixed scleral-suture strabismus surgery generally produces a postoperative undercorrection drift, especially following recession surgery, exotropia or overcorrection at the first postoperative week.