Orbital Pseudotumor

Ophthalmologists in the early 1800s made an interesting observation that several patients with presumed orbital tumors showed spontaneous improvement without any treatment. Until then proptosis was considered as prima facie of orbital neoplasm. Panas coined the term “pseudoplasm” for these puzzling cases. Birchfield in 1930 used the term orbital pseudotumor for such cases. Improvements in diagnostic techniques as also better understanding of the pathology of orbital pseudotumor helped us to define orbital pseudotumor as a nonspecific idiopathic, benign inflammatory process characterized by polymorphous lymphoid infiltrate with varying degrees of fibrosis. It is also known as idiopathic orbital inflammatory syndrome (IOIS). Pseudotumor orbit accounts for 10% of orbital tumors. The peak incidence of the condition is in fourth and fifth decade but it can also occur in children. There is no sex predilection. It is usually unilateral though bilateral involvement is possible in children. Orbital pseudotumor is usually a monophasic illness but it can be recurrent, especially in children. It remains a diagnosis of exclusion, as it is diagnosed after excluding orbital tumors, thyroid eye disease and systemic inflammatory disease. IOIS is characterized by its chronicity, and classified based on anatomic location, or histologic subtype .