Clinical characteristics of patients that experience different rates of exodrift after strabismus surgery for intermittent exotropia and the effect of the rate of exodrift on final ocular alignment.

PURPOSE: To evaluate the ocular motility factors associated with the rate of exodrift after surgical correction of intermittent exotropia and to determine whether the rate had an effect on the subsequent postoperative ocular alignment.
METHODS: Consecutive patients who underwent surgical correction of intermittent exotropia between 2009 and 2010 were observed for 12 months. Patients were divided into two groups, according to the averaged value of the rate of exodrift (fast vs slow). The ocular motility characteristics of the patients in each group were compared with identify factors that correlated with the speed of postoperative exodrift and to determine whether the rate had an effect on the final ocular alignment at 12 months after surgery.
RESULTS: A total of 159 patients underwent strabismus surgery during the study period. Of these, 130 experienced postoperative drift. The preoperative deviation at near and distance differed significantly between the fast and slow groups (P < 0.05) and was correlated to the rate of exodrift (near r = 0.427, distance r = 0.378): fast group, 32.09(Δ) ± 10.07(Δ), 27.60(Δ) ± 6.65(Δ); slow group, 31.74(Δ) ±10.34(Δ), 27.21(Δ) ± 6.03(Δ). The deviation at the first day after the surgery differed significantly between groups (P < 0.05) and was correlated to the rate of drift (r = 0.381): fast group, 4.72(Δ) ± 5.46(Δ) esotropia; slow group, 1.87(Δ) ± 4.40(Δ) esotropia. The two groups did not differ significantly in other factors. There were no differences in ocular alignment at 12 months' follow-up.
CONCLUSIONS: The rate of exodrift correlated with the size of the preoperative deviation and the amount of the initial postoperative overcorrection. It had no affect on the ocular alignment at 12 months after surgery.