Combined Orbital Decompression and Rectus Muscle Myectomy for Large-Angle Strabismus in Thyroid-Associated Orbitopathy

INTRODUCTION: Thyroid-associated orbitopathy (TAO) often causes restrictive strabismus and diplopia. Large-angle deviations pose particular challenges owing to extraocular muscle fibrosis and unpredictable surgical dose-response. Although combined orbital decompression and strabismus correction has been proposed to reduce the number of procedures, its effectiveness in large-angle TAO remains uncertain. This study aimed to evaluate the outcomes of combined orbital decompression and rectus muscle myectomy in this population. METHODS: In this retrospective cohort study, 88 patients with TAO-associated strabismus > 25 prism diopters (PD) underwent either staged (step) surgery (n = 42) or combined surgery (n = 46) at a tertiary center between 2018 and 2022. All had stable thyroid function for ≥ 6 months before surgery. The combined procedure involved simultaneous orbital decompression and rectus myectomy. Outcomes included deviation angles, Hertel exophthalmometry, and the field of binocular single vision (BSV). RESULTS: Baseline characteristics were comparable between groups. Postoperatively, the combined-surgery group had smaller residual horizontal and vertical deviations-median 0 (0-3) and 2 (0-3) PD-than the step group, 5 (4-5) and 3 (3-5) PD (all p < 0.001). The BSV field was wider after combined surgery [410 (396-426)° versus 360 (328-386)°, p < 0.001]. Overall success rates (≤ 5 PD deviation in primary and reading positions) were similar (84.8% versus 81.0%, p = 0.633). Transient lower lid retraction occurred in a few patients and was successfully corrected. CONCLUSIONS: Combined orbital decompression with rectus myectomy achieved effective alignment and superior binocular function compared with staged surgery, offering a practical and safe option for TAO-related large-angle strabismus.