To investigate the effect of unilateral medial rectus resection in recurrent exotropia under 25 Prism Diopter after unilateral or bilateral lateral rectus recession.

A retrospective chart analysis was conducted for 21 patients who underwent unilateral medial rectus resection for recurrent exotropia under 25PD and uni- or bilateral lateral rectus recession for prior surgery of exotropia. The medial rectus was resected from 5.0 to 7.0 mm by 0.5 mm according to angle deviation at a distance. The postoperative deviated angle was checked at one week, three months and six months postoperatively to investigate the amount of corrected deviation per resected muscle.

The average preoperative deviation was 20.57±3.37PD. We resected mean 6.1±0.62 mm of the medial rectus. At one week after the surgery, the postoperative deviated angle was 2.00±4.32PD, After six months it was 6.57±7.40PD, and there appeared to be an increase of deviation. Ten patients (48%) fused before surgery and 12 (57%) after surgery. The corrected deviation per resected muscle was 2.88±1.08PD.

Unilateral medial rectus resection is an effective surgical method for the treatment of recurrent exotropia under 25 PD after lateral rectus recession.