Eye Proptosis in Dogs
Overview of Canine Eye Proptosis
Proptosis is displacement of the eyeball out of the eye socket, so that the eyelids are trapped behind the globe. Proptosis typically occurs in dogs following trauma to the face or head.
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, and Boston terrier, 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.
The prognosis for retaining vision after proptosis is poor.
Causes of Eye Proptosis in Dogs The most common cause of proptosis in small breed dogs is a fight with a larger dog. In a dog fight, the larger dog tends to grab the small dog by the scruff of the neck. Pulling the skin back over the head allows the eye to pop forward. Another cause of proptosis in the dog is blunt trauma to the face and head. This can occur from being struck by an object, such as a baseball bat, shovel, car or motorcycle. Proptosis from blunt trauma can occur in any type of dog. In brachycephalic dogs with very shallow orbits, the eye is not well protected at all. Some of these dogs also have excessively large openings of the eyelids. In these dogs manual restraint or inadvertent pulling on the skin over the head or neck may result in proptosis.
Diagnosis of Proptosis in Dogs
Proptosis is considered a true eye emergency. Diagnosing proptosis is based on physical exam findings. The eye protrudes from the socket with the eyelids curled behind it. The lids cannot cover the eye and the surface of the eye rapidly becomes dry and discolored. In severe cases, the muscles of the eye may be torn so that the eye is deviated outward or is attached by only a few thin strands of tissue.
For proptosed eyes secondary to head trauma, a thorough physical examination concentrating on the face is crucial and may reveal other potentially serious complications. It is not uncommon for the bones of the face and jaw to be fractured in long nose (dolichocephalic) breeds of dogs.
Additional tests may include: Examination of the eye to determine the extent of injury. This can help determine the course of treatment. Staining of the cornea (superficial clear layer of the eye) to detect cuts, scratches or abrasions on the surface Examination of the interior of the eye for bleeding within the eye or inflammation in the front chamber of the eye. In eyes with significant bleeding, the interior of the eye may not be visualized. Examination of the muscles, skin and nerves attached to the proptosed eye. If the muscles surrounding the eye are seriously damaged or if the optic nerve behind the eye is torn, then removal of the eye is recommended.
Treatment for Dogs with Eye Proptosis
Initially, lubricant or antibiotic ointments are applied to the injured eye in an attempt to reduce further damage to the cornea. Based on the severity of injury, the treatment options are enucleation (removal of the eye) or replacement of the eye back into the socket. Unless severely damaged, replacing the eye and allowing time for it to heal is the preferred treatment. A stable dog is placed under general anesthesia, and the eye is gently pushed back into the socket. In some situations, an incision may be made in the outer edge of the eyelid to allow more space for the eye to be replaced into the bony socket. After replacing the eye, the outside eyelids are sutured closed. This surgery is called a temporary tarsorrhaphy. Topical antibiotics and atropine are then administered through the eyelids to help decrease the dog’s pain and aid in healing of the cornea. After one to two weeks the eyelid sutures are removed. At this point, the eye is reevaluated and vision tests are performed. When proptosis is complicated by serious head trauma, surgery on the eye may be delayed until after the brain concussion has resolved. If the dog is unconscious, the eyelids may be sutured closed without anesthesia. If anesthesia must be delayed for several days, then an enucleation is performed once the animal is stable. If the optic nerve is torn or if the eyeball is attached by only a small amount of tissue, enucleation is the preferred treatment. Unfortunately, the prognosis for vision is always poor and is based upon the degree of trauma that was delivered to the eye. Even if vision is lost, rapid treatment can result in salvaging the eye for cosmetic reasons.
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