Proptosis in Small Animals

Proptosis is a sudden anterior displacement of the globe, with entrapment of the eyelids behind the equator of the globe; it requires surgical replacement or globe removal depending on the extent of damage to the eye and its surrounding structures.

Proptosis (sudden anterior displacement of the globe) is most commonly caused by blunt trauma (eg, being hit by a car, fighting with another animal; see traumatic proptosis image). 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.

Proptosis, dog

Image

Courtesy of Dr. K. Gelatt.

The prognosis depends on the following factors:

• pupil size and reflexes

• duration of exposure

• other globe or orbital damage

• breed (brachycephalic breeds 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 (see temporary tarsorrhaphy image).

Temporary tarsorrhaphy for proptosis, dog

Image

Courtesy of UC Davis Comparative Ophthalmology Service.

This procedure should be followed by administration of systemic antimicrobials and corticosteroids as well as topical antimicrobials 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 the following:

• blindness due to optic nerve degeneration

• corneal ulceration

• enophthalmia

• keratoconjunctivitis sicca

• lateral strabismus due to medial rectus muscle injury