Risk Factors for Excessive Postoperative Exo-Drift after Unilateral Lateral Rectus Muscle Recession and Medial Rectus Muscle Resection for Intermittent Exotropia

Background To detect significant factors associated with excessive postoperative exo-drift in young patients with intermittent exotropia who had undergone unilateral lateral rectus muscle recession and medial rectus muscle resection. Methods We retrospectively examined the records of 64 consecutive patients < 18 years old who underwent surgery between April 2004 and December 2011. We sought risk factors for excessive postoperative exo-drift among patients’ demographic and clinical characteristics using univariate and multivariable linear regression analysis. Results Younger patients ( P = 0.007), and those with larger preoperative exo-deviation at distance ( P = 0.033), a lower incidence of peripheral fusion at distance ( P = 0.021) or a greater postoperative initial eso-deviation ( P = 0.001), were significantly more likely to have an excessive postoperative exo-drift (> 20 prism diopters). Univariate analysis revealed significant associations between excessive postoperative exo-drift and age at surgery ( P = 0.004), preoperative exo-deviation at distance ( P = 0.017) and postoperative initial eso-deviation at distance ( P < 0.001). Multivariable linear regression analysis showed that postoperative initial eso-deviation at distance ( P = 0.008) was significantly associated with postoperative exo-drift. Conclusions Postoperative exodrift in unilateral RR is predicted by the initial postoperative eso-deviation, which may offset the overcorrection. However, the exo-drift is greater in cases with a large preoperative exo-deviation and/or at a younger age, and should be followed carefully.