The aim of this study was to evaluate and compare the efficacy of intravenous (iv) glucocorticoids (GCs) with and without orbital radiotherapy (ORT) in a retrospective analysis of patients with active, moderate-to-severe Graves' orbitopathy (GO). Since diplopia has the strongest impact on quality of life, a careful work up of motility and binocular single vision (BSV) has been performed. The Essen-EUGOGO-Center database (n=3655) was screened for patients with untreated moderate-to-severe, active GO, onset ≤12 months. The inclusion criteria were met by 148 patients (n=76 ivGC, n=72 ivGC + ORT). We analyzed CAS (inactivation: ≤2), NOSPECS, lid-width, proptosis, motility, and field of BSV. To score the overall ophthalmic outcome, a severity-weighted-score (SOS) was compared with an established EUGOGO inflammation-weighted-score (IOS). Cumulative ivGCs dosages and duration of GO did not differ between the groups. Patients with combination therapy had a significantly more severe GO at baseline. Therefore, a subgroup with matched severity was additionally compared. In the IOS, both groups reached similar improvement rates (55.2 vs. 63.9%; p=0.31). However, in the SOS, the rates differed significantly (46.1 vs. 61.1%; p=0.03- unmatched and p=0.03 matched), despite similar rates of inactivation (65.8 vs. 63.8%). Impaired motility improved significantly more often after combination therapy (p=0.01 matched, p=0.004 unmatched). Treatment responders showed only partial improvement (proptosis: 2.5±0.5 mm; motility: 11.3±10.9°). In our retrospective analysis, combination therapy (ivGCs + ORT) was significantly more effective in reduction of severity and should therefore always be considered in moderate-to-severe GO stages, especially in the presence of motility disorders. However, the limited improvement in clinical parameters, despite the promising effect on inactivation of inflammation, has to be outlined to the patients.