Proptosis is most commonly caused by blunt trauma (eg, being hit by a car, fight with another animal). During trauma, the globe is displaced from the orbit, and the eyelids are entrapped behind the globe, thus preventing return of the globe to its normal position. Secondary orbital hemorrhage and swelling displace the globe further from the orbit. Corneoconjunctival drying and ulceration follow.
Prognosis depends on:
pupil size and reflexes
duration of exposure
other globe or orbital damage
breed (brachycephalics are predisposed)
other systemic trauma
Approximately 25% of dogs recover vision, whereas the prognosis for vision in cats is grave.
Treatment begins by providing moisture to lubricate the exposed cornea and conjunctiva. A lateral canthotomy and complete temporary tarsorrhaphy with usually two or three interrupted horizontal mattress sutures with stents (placed at one-half thickness of the eyelids) is performed under general anethesia. This should be followed by systemic antibiotics and corticosteroids as well as topical antibiotics and mydriatics (if miosis is present). Sutures and stents are removed only when the swelling is gone and a brisk blink reflex returns (usually 14–21 days); the most medial sutures and stents can be removed initially so the eye can be examined. Premature suture removal results in lagophthalmia and persistent and often progressive corneal ulceration.
Complications after traumatic proptosis include:
blindness due to optic nerve degeneration
lateral strabismus due to medial rectus muscle injury