Decreased postoperative drift in intermittent exotropia associated with A and V patterns.

INTRODUCTION: Few data exist concerning postoperative drift in patients with intermittent exotropia who have coexistent A or V patterns. In addition, the impacts of pattern collapse and surgical method on postoperative drift have not been well addressed.

METHODS: We retrospectively reviewed the records of 132 patients who had surgery for intermittent exotropia and had >or=6 months' follow-up. Mean postoperative drift in 66 patients with pattern exotropia was compared with a nonpattern (comitant) group matched for surgeon, age, surgical method, and initial deviation. Postoperative drift was calculated by subtracting the deviation at postoperative day 1 from that at approximately 6 weeks, 6 months, 9 months, and >1 year.

RESULTS: Pattern and comitant groups were similar in mean +/- SD age (15 +/- 17 years), follow-up (2.3 +/- 2 years), preoperative exotropia (23(Delta) +/- 11(Delta)), initial postoperative deviation (1(Delta) +/- 5(Delta) esotropia), and surgical technique. Patients with pattern intermittent exotropia showed significantly (p < 0.02) less exotropic drift postoperatively at all times than did patients without a pattern. In contrast to undercorrected patients, in those who were sufficiently overcorrected, the effect of pattern became statistically insignificant after 6 months. Patients with persisting postoperative patterns had a significantly less postoperative drift (p < 0.01).

CONCLUSION: Postoperative drift in patients with A- or V-pattern intermittent exotropia is consistently less than in comitant exotropia, particularly if the pattern persists postoperatively and if the exotropia is undercorrected. Therefore, surgeons should consider smaller early overcorrections in pattern than comitant intermittent exotropia. Lesser postoperative drift in pattern exotropia may suggest differing underlying causes of pattern vs nonpattern exotropia.