Diagnosis
The two most common diagnoses for this condition include:
Bupthalmia When the globe of the eye has become enlarged. The eyelids are still properly positioned, but the eyelid cannot cover the eye.
Exophthalmia When the globe of the eye has been displaced forward, causing it to protrude from the normal eye socket location.
Causes
Due to differences in facial conformation, certain breeds of dog are more prone to eye proptosis than others. In dog breeds with long noses and eyes set deep into the bony socket, such as Collies, proptosis of the eye is rare. In dog breeds with prominent, bulging eyes, short noses, and shallow sockets (brachycephalic dogs), such as the Shih Tzu, Pekingese, Pug, Lhasa apso, Boston Terrier, and Chihuahua, proptosis is a much more common problem. Some of these brachycephalic dogs have such loosely set eyes that even mild restraint or play can result in eye proptosis.
Treatment
About 20-40 percent of proptosed eyes retain vision after being replaced in the orbit. Replacement of the eye requires general anesthesia. The eyelids are pulled outward, and the eye is gently pushed back into place. The eyelids are sewn together in a procedure known as tarsorrhaphy for about five days to keep the eye in place. Replaced eyes have a higher rate keratoconjunctivitis sicca and keratitis and often require lifelong treatment. If there is severe damage, the eye is removed in a relatively simple surgery known as enucleation of the eye.
Prognosis
The prognosis for a replaced eye is determined by the extent of damage to the cornea and sclera, the presence or absence of a pupillary light reflex, and the presence of ruptured rectus muscles. The rectus muscles normally help hold the eye in place and direct eye movement. Rupture of more than two rectus muscles usually requires that the eye be removed, because there is usually also significant blood vessel and nerve damage. Compared to brachycephalic breeds, dochilocephalic (long nosed) breeds usually have more trauma to the eye and its surrounding structures, so there is a worse prognosis.
