To evaluate the characteristics and surgical outcomes of children with intermittent exotropia whose preoperative angle of deviation changed on the day of surgery.

The medical records of 323 children with intermittent exotropia who underwent lateral rectus recession in both eyes were reviewed. The records were classified according to the difference of 8 prism diopters (PD) or more between the largest angle of deviation measured within 3 months prior to the operation and that on the day of surgery into the increased, same, or decreased groups. The frequency, characteristics, and surgical outcomes of each group were analyzed. The surgical amount was determined based on the largest angle of deviation measured at distance within 3 months before surgery.

The angle of deviation at distance on the day of surgery was increased in 5 patients (1.5%) and decreased in 6 (1.9%). The near angle was increased in 19 (5.9%) and decreased in 22 (6.8%) patients. The groups in which distant deviation was changed had a greater distant angle and more patients with anisometropia. The group in which near deviation decreased was older than the same group and 81.8% of the patients were school-aged. In the group with changes in either distant or near deviation, the angle on the day of surgery changed toward decreasing disparity of near-distant deviation. On the last follow-up, the rate of overcorrection of 10 PD or more was 13.6% in the decreased near deviation group, which was significantly high ( p = 0.039).

The angle of deviation on the day of surgery could be different compared to the largest preoperative angle in some patients with intermittent exotropia. In patients with decreased near deviation, the rate of postoperative overcorrection might be high.