Stereopsis before and after Inferior Oblique Weakening Surgery

PURPOSE: To analyze stereopsis change before and after inferior oblique weakening surgery. METHODS: We retrospectively reviewed the medical records of 31 patients who had undergone inferior oblique weakening surgery. The factors analyzed included sex, age at surgery, preoperative and postoperative visual acuity (VA), time from first detection to surgery, degree of inferior oblique overaction (IOOA), primary/secondary IOOA, exotropia/hypertropia, bilaterality, and type of surgery. RESULTS: Eighteen patients with a mean age 7.3 ± 3.1 years exhibited stereopsis of 60 arc seconds or better before surgery and 17 had stereopsis better than 60 arc seconds after surgery. Postoperatively, stereopsis improved in 13 patients and deteriorated in 9. Better preoperative VA and the absence of superior oblique underaction were associated with better preoperative stereopsis. Better preoperative VA, postoperative VA, and the presence of head tilt were associated with better postoperative stereopsis. Unilateral inferior oblique weakening surgery and accompanying hypertropia were associated with improved stereopsis, while the absence of hypertropia was associated with deteriorated stereopsis. CONCLUSIONS: In this retrospective study, 58.1% of patients tended to have bifoveal fixation. When a vertical deviation is present in the primary position due to unilateral IOOA, IO weakening surgery can be expected to improve binocular function.