Consecutive Esotropia Following Exotropia Surgery: Possible Risk Factors, Changes in the Angle of Deviation, and Esotropia Rates

OBJECTIVES: To evaluate the risk factors associated with consecutive esotropia, as well as the changes in deviation angle and the prevalence of esotropia in patients who underwent surgery for exotropia.
METHODS: The records of patients with basic-type exotropia who underwent either bilateral lateral rectus recession (symmetric surgery) or unilateral lateral rectus recession combined with medial rectus resection (asymmetric surgery), and who were followed for at least one year, were retrospectively reviewed. Preoperative, early postoperative, and late postoperative findings were analyzed for both groups: symmetric surgery (Group 1) and asymmetric surgery (Group 2). Consecutive esotropia was defined as ≥5 prism diopters of esotropia at either distance or near fixation.
RESULTS: Of the 114 patients included, 52 (46%) were female and 62 (54%) were male. The mean age at surgery was 20.42 years in Group 1 and 15.59 years in Group 2 (p>0.05). Group 2 had significantly lower visual acuity, stereopsis, and fusion rates, and higher rates of amblyopia and anisometropia compared to Group 1. At the final follow-up examination, the deviation angles decreased significantly in both groups (p<0.001), and the prevalence of consecutive esotropia reduced from 17% to 7% in Group 1 and from 30% to 19% in Group 2 (p=0.031). While stereopsis did not significantly improve postoperatively in Group 1, increased significantly in Group 2 (p=0.031). Fusion improved significantly in both groups (p<0.001). Refractive error, anisometropia, preoperative and early postoperative deviation angles, and the extent of surgery were identified as significant risk factors for consecutive esotropia (p<0.05).
DISCUSSION AND CONCLUSION: Although initial overcorrection following exotropia surgery tends to decrease over time, patients with high preoperative and early postoperative deviation angles, high refractive errors, anisometropia, and greater surgical amounts should be carefully monitored for the development of consecutive esotropia.

Keywords: Asymmetric surgery, consecutive esotropia, diplopia, exotropia, symmetric surgery