Comparison of outcomes of unilateral recession-resection as primary surgery and reoperation for intermittent Exotropia

BACKGROUND The aim of this study was to compare the primary surgery and reoperation outcomes of unilateral lateral rectus recession and medial rectus resection (R&R) for intermittent exotropia. METHODS We retrospectively reviewed the medical records of 80 patients, all of whom had undergone unilateral R&R for intermittent exotropia as a primary surgery or reoperation and been followed-up on postoperatively for 6 months or more. The patients were divided into two groups: unilateral R&R as primary surgery (group A, 44 patients) and unilateral R&R as reoperation (group B, 36 patients). The outcome measures were postoperative angle of deviation, surgical success rate, and mean dose-effect ratio (PD/mm, corrected angle of deviation / sum of amount of recession of lateral rectus and of resection of medial rectus). Surgical success was defined as exo- or esodeviation within 8 PD. RESULTS The mean postoperative follow-up duration was 49.91 ± 14.83 months in group A and 43.17 ± 26.91 months in group B (p = 0.160). The mean angles of deviation at postoperative 1 day were -5.18 PD (overcorrection) in group A and -5.28 PD in group B (p = 0.932). However, there was a significant difference in the mean angle of deviation between the two groups at each visit from postoperative 3 months to final follow-up (p < 0.05): in short, group A had become more exotropic than group B. And the surgical success rate was higher in group B than in group A at each visit from postoperative 12 months to final follow-up (47.7% in group A and 83.3% in group B at final follow-up) (p < 0.05). The mean dose-effect ratio at 6 months after surgery was 1.89 ± 0.58 PD/mm in group A and 2.26 ± 0.32 PD/mm in group B (p = 0.001). CONCLUSIONS Unilateral R&R as reoperation presented better results for the surgical treatment of recurrent exotropia, showing a smaller exodrift pattern and higher surgical success rates compared with R&R as a primary surgery. The mean effect per millimeter (the mean dose-effect ratio, PD/mm) of R&R as reoperation was significantly greater than that of R&R as primary surgery at postoperative 6 months. These results could serve as useful guidelines in the planning of surgical correction for primary and recurrent exotropia.