Dynamic realignment of extraocular muscles after inferomedial orbital wall decompression in thyroid eye disease: a 3D CT reconstruction study.

Orbital wall decompression carries a risk of new-onset postoperative diplopia in patients with thyroid eye disease (TED). This study aimed to evaluate the occurrence, clinical progression, and underlying mechanisms of new-onset diplopia following inferomedial orbital wall decompression over 1 year, including quantitative CT analysis of orbital structures. Inactive TED patients undergoing inferomedial orbital wall decompression were reviewed. Only patients who developed new diplopia at 1 month and completed a 1-year follow-up were included. Diplopia cases were assessed using Gorman scores and HESS tests. Orbital structures and deviated angles of the medial and inferior rectus muscles were quantified on CT images. New-onset diplopia occurred in 35% (78/204) of patients at 1 month postoperatively, with 73.2% recovering fully from diplopia by 1 year. In the recovered-diplopia group, orbital volume decreased significantly from immediate postoperative to 1 year (p = 0.038) but not in the persistent-diplopia group. Additionally, the rectus muscles, deviated immediately after surgery, showed significant straightening at 1 year in the recovered-diplopia group (p < 0.001), while no significant improvement in muscle alignment was observed in the persistent-diplopia group. New-onset diplopia after inferomedial orbital wall decompression is typically transient, resolving within 1 year. The resolution is mediated by muscle realignment driven by orbital remodeling and muscle contraction.