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

Abstract

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. 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). 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. 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.