Correlation Between Changes in Extraocular Muscles and Intraocular Pressure Following Anti-Inflammatory Therapy in Active Thyroid Eye Disease

<b>Objectives</b>: We investigate the correlation between functional and morphological changes in extraocular muscles (EOMs) and intraocular pressure (IOP) changes before and after thyroid eye disease (TED) treatment. <b>Methods</b>: A multicenter study with a retrospective chart review was conducted. Patients with active TED receiving corticosteroid therapy without glaucoma eye drops between 2014 and 2023 were reviewed. Various parameters were measured by magnetic resonance imaging. The primary outcome measure was the correlation between changes in the IOP and the cross-sectional area (CSA) of the EOMs before and after treatment. Secondary outcome measures were comparisons of IOP, the signal intensity ratio (SIR) of the EOMs and orbital fatty tissue (OFT), and the CSA of the EOMs before and after treatment. <b>Results</b>: The IOP in 99 eyes in 51 patients significantly decreased from 18 ± 3.4 mmHg to 15.5 ± 2.9 mmHg before and after treatment (<i>p</i> < 0.01)). The CSA and SIR of all EOMs and OFT significantly decreased after treatment (<i>p</i> < 0.05). Factors that had a significant positive correlation with the IOP change rate before and after treatment were the CSA change rate of the inferior rectus muscle (IRM) before and after treatment (Spearman's correlation coefficient, R² = 0.24, <i>p</i> < 0.05) and the CSA change rate of the total EOMs before and after treatment (Spearman's correlation coefficient, R² = 0.22, <i>p</i> < 0.05). <b>Conclusions</b>: In TED patients, IOP decreased with anti-inflammatory treatment alone. The most significant parameter that correlated with the decrease in IOP was the CSA change rate of the IRM.