Idiopathic orbital inflammation (IOI), or orbital pseudotumor, is a benign, non-infectious condition representing 8–10% of orbital mass lesions. This article presents a rare case of idiopathic orbital myositis (IOM) in a 45-year-old diabetic woman, who presented with acute right eye pain, diplopia, and motility deficits. Magnetic Resonance Imaging (MRI) revealed typical signs of inflammation, including hyperintense signals in T2-weighted Turbo Spin Echo (TSE) and Short Tau Inversion Recovery (STIR) sequences, along with post-contrast enhancement. Notably, there was no muscle belly enlargement, and the patient did not respond to corticosteroid therapy. Strict glycemic control, however, led to clinical improvement, suggesting a potential link between diabetes and IOM. Additionally, a comprehensive literature review on imaging in IOM was conducted, covering articles published from 2000 to 2024. The review highlights MRI as the primary diagnostic tool for IOM, offering a high sensitivity and specificity in differentiating it from other orbital conditions. This case underscores the importance of modern imaging techniques in diagnosis and emphasizes the need for continued research in evidence-based medicine, especially in complex cases where disease boundaries are not clearly defined.