An Expert Panel of the Orbital Society reported criteria for the diagnosis of nonmyositic idiopathic orbital inflammation (IOI). The criteria were developed by a Delphi consensus approach amongst expert ophthalmologists. 

Idiopathic Orbital Inflammation (IOI) may occur as a diffuse myositis (myositic) or as inflammation without diffuse myositis (nonmyositic).


The age of onset is typically from 10 to 75 years of age.


Features of nonmyositic IOI:

(1) diffuse orbital mass

(2) contrast-enhanced

(3) orbital pain

(4) acute or subacute onset

(5) unilateral

(6) no history of systemic disease involving the orbit

(7) adjacent paranasal sinuses are normal

(8) compatible laboratory and pathologic findings


Involvement of the lacrimal gland may be seen as a diffuse swelling.

Involvement of orbital fat shows irregular margins.

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