Risk factors:
(1) surgical correction of ptosis
(2) cosmetic blepharoplasty
(3) eyelid trauma
(4) frontal sinus surgery
(5) removal of neurofibromas or other tumor
Muscles usually affected:
(1) tendon of the superior oblique muscle (affected by upper eyelid surgery)
(2) inferior rectus muscle (affected during lower eyelid surgery)
(3) rarely the medial rectus or one of the other extraocular muscles
Features:
(1) No evidence of strabismus prior to surgery.
(2) Onset of diplopia or strabismus following the surgery.
(3) The affected muscle or its tendon was within the operative field.
