This study is to investigate the impact of the coexistence of basic intermittent exotropia and vertical incomitance in the form of the V and sub-V pattern on the results of surgical correction of intermittent exotropia.

The records of 81 pediatric patients who had surgery for intermittent exotropia and a follow-up of more than 1 year were reviewed retrospectively. They were divided into groups: a concomitant group which underwent only horizontal muscle surgery of bilateral lateral rectus recession and a V pattern group which had additional inferior oblique recession, further separated into two subgroups: ≥ 15 prism diopters (classic V pattern group) and ≥ 10 < 15 prism diopters (sub-V pattern group). The surgical outcome, deviation control, stereoacuity, and postoperative drift were assessed after 3 months and 1 year postoperatively.

Patients with sub-V and classic V pattern intermittent exotropia showed significantly better surgical success rate (p = 0.025) and less postoperative drift (p = 0.042) than patients without vertical incomitance. One year after surgery, successful surgical outcome was achieved in 83.72% of the vertically incomitant group: 80.76% for the classic V pattern and 88.24% for the sub-V pattern group, while only in 60.53% of nonpattern patients.

Patients operated for intermittent exotropia with a coexistent V pattern have consistently better surgical long-term results than those with only horizontal deviation. Additional inferior oblique recessions in the sub V pattern group provided excellent outcomes with no overcorrections; therefore, surgeons should consider addressing vertical incomitance even when the typical criteria for the V pattern are not met.