Idiopathic Orbital Inflammation

Idiopathic orbital inflammation (IOI) is a poorly understood orbital disorder characterised by a soft tissue mass or enlarged structure featuring nonspecific orbital inflammation of unknown origin. Most commonly the lacrimal gland, extraocular muscles, or orbital fat are affected, but multiple structures can be involved. IOI constitutes a diagnostic challenge for the lack of robust distinguishing clinical and imaging features. In a clinicoradiological context suggesting IOI, lesions of the lacrimal gland and orbital fat require biopsy to histologically confirm compatibility with IOI and exclude other disorders, while idiopathic orbital myositis may be diagnosed based on corticosteroid responsiveness. Treatment is tailored to affected structures, severity of symptoms and progress of disease, and includes surgical debulking, non-steroidal anti-inflammatory drugs, corticosteroids, radiation therapy, other immunomodulating drugs and biological agents.