The condition affects women twice as often as men and typically presents in early adulthood.
Clinical features of orbital myositis:
(1) The onset is usually acute or subacute.
(2) The patient presents with diplopia with or without ptosis.
(3) There is a painful ophthalmoplegia.
(4) There is often conjunctival injection and/or chemosis.
(5) There is usually preservation of visual acuity.
(6) There are characteristic changes on orbital MRI (see below).
(7) The patient often shows a rapid response to corticosteroid therapy but refractory cases occur.
There are 2 clinical forms based on the severity of the inflammation:
(1) limited oligosymptomatic ocular myositis (LOOM)
(2) severe exophthalmic ocular myositis (SEOM) with chemosis, pupillitis and proptosis
MRI findings
(1) The changes can be seen in T2-weighted or contrast-enhanced T1 with fat suppression
(2) There is thickening of the affected extra-ocular muscle (EOM) at the myotendinous junction with contrast enhancement of adjacent fat
The diagnosis requires exclusion of other causes of ophthalmoplegia.
