To evaluate the relationship between velocity of exotropic drift and recurrence after surgical correction of intermittent exotropia.

The medical records were retrospectively reviewed preoperatively and at the following postoperative time periods: 1 and 5 weeks and 3, 6, and 12 months. The monthly change in alignment velocity in patients who demonstrated tendencies of exotropic drift was measured. The correlation between each data point and the velocity of total period (from 1 week to 12 months) was analyzed. According to the best correlated velocity of the time period, the patients were divided into 2 groups, and the motor success rates were assessed. Each group was further divided into 3 subgroups (esotropia, orthophoria and exotropia) according to angle of deviation at 1 week, and motor success rates were assessed again.

Exotropic drift tendency was exhibited in 113 patients (91.13%). The mean postoperative monthly change in alignment velocity of total period showed the highest correlation with 1 month (Pearson, r = 0.61). The 2 groups divided by 3.57 PD/M were not different in motor success rate. The group showing exotropia at 1 week and high exotropic drift velocity at 1 month had a low success rate (Mann-Whitney, p = 0.03).

The velocity of exotropic drift at postoperative 1 month best reflected the total velocity but did not influence the recurrence rate. Based on the results from the present study, patients with exotropia and high exotropic drift velocity at postoperative 1 month have a greater likelihood of recurrence compared to the others.