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

Abstract

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 newonset 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.