Figure 1 (above). Proptosis in an Australian shepherd puppy.
Proptosis of the globe (Figure 1) is a true ocular emergency. The eyelids become trapped behind the equator of the globe, usually from trauma. The eyelid margins are seldom visible, and the patient is unable to blink and protect the cornea. Treatment delay and resultant elongated globe exposure can increase the likelihood of corneal ulceration, retrobulbar edema, and hemorrhage, raising the risk for blindness from globe perforation or optic nerve damage.
The force necessary to proptose a globe varies with orbital anatomy. Proptosis occurs more easily in brachycephalic breeds (both canine and feline) than in mesocephalic or dolichocephalic breeds, improving the odds for sight and globe retention in the former. The prognosis for vision is generally guarded to poor, but prompt treatment may save the globe. Enucleation may be best if the globe is ruptured or ≥2 extraocular muscles or the optic nerve is avulsed. If the status of the eye and muscles cannot be determined, proptosis should be reduced and a temporary tarsorrhaphy placed. The globe can be removed later if necessary, but it cannot be replaced.
Following surgery, the eye should be monitored for signs of keratoconjunctivitis sicca, a common sequela that requires frequent, diligent, and long-term medical therapy even if the globe has been rendered nonvisual. If owners are unwilling or unable to provide long-term care following resolution of proptosis, enucleation at initial presentation may be warranted.