Evaluation of ocular findings in patients with thyroid eye disease: Is medial rectus insertion involvement a clinical activity marker?

PurposeThis study aimed to investigate the relationship between extraocular muscle (EOM) insertion involvement and clinical activity in patients with thyroid eye disease.MethodsThis cross-sectional retrospective study included 292 eyes from 292 patients who underwent comprehensive ophthalmologic examination. Patients were divided into two groups based on the presence (Group 1) or absence (Group 2) of medial rectus muscle insertion involvement. Involvement was defined as hypertrophy and/or vascularization of the muscle insertion observed on slit-lamp examination. Ophthalmologic assessment included best-corrected visual acuity (BCVA, LogMAR), refractive error, intraocular pressure (IOP), slit-lamp examination of the anterior segment, dilated fundus examination, and Hertel exophthalmometry for both eyes. Additionally, magnetic resonance imaging (MRI) findings were evaluated for all patients.ResultsOur study included 71 patients in group 1 and 221 patients in group 2. The mean follow-up period was 4 ± 2 (2-8) years. Clinical activity score (CAS) and HE values were statistically significantly higher in the first group (p < 0.001). MRI analysis revealed significantly greater EOM enhancement in Group 1 (p < 0.05). Among patients with insertional involvement, 45 had CAS ≥ 4 and 26 had CAS ≤ 3. Statistically significant regression was observed in the CAS of patients with CAS ≤ 3, with insertional involvement and who were started on corticosteroid treatment.ConclusionThe CAS was significantly higher in patients with medial rectus insertion involvement on biomicroscopic examination (p < 0.001), suggesting that this finding may serve as an additional indicator of disease activity.