“…Because the diagnosis of IOI is a diagnosis by exclusion, a physical examination and clinical history are essential to rule out associated diseases, including systemic immune diseases such as orbital cellulitis, optic neuritis, TO, sarcoidosis, histiocytosis, Wegener's granulomatosis, Tolosa-Hunt syndrome, optic nerve gliomas, lymphomas, and other malignancies. Infection is a common cause of IOI, which can be hidden in surrounding orbital structures [24,25].…”