Shih Tzu breeder Nancy Stern had noticed that her 3-year-old champion show dog, “Ledger,” was having problems keeping his eyes open and seemed bothered by sunlight or bright light. Large, round eyes and a pushed-in face are among the prominent features of this lively toy breed.
Stern, who lives in Dunnellon, Fla., took Ledger to see an ophthalmologist at the University of Florida Small Animal Hospital in Gainesville. The diagnosis was corneal ulcers caused by distichiasis, a condition in which an additional row of eyelashes, or cilia, develop along the edge of the eyelids. Though the eyelashes don’t always turn inward, in Ledger’s case they did, irritating the cornea every time he blinked. The little dog had an advanced case with pustules that had formed beneath the eyelids.
Surgery was performed to remove the extra eyelashes and pustules. Recovery took about three weeks and involved application of an antibiotic ointment three times a day and a serum from Ledger’s own blood. “The serum definitely helped to heal the ulceration in the eye,” Stern says.
About three weeks after surgery, Ledger experienced a setback. Some of the eyelashes caused by distichiasis were missed in surgery and were irritating the cornea. Once they were removed, he began to recover completely.
Stern cautions owners of Shih Tzu to seek veterinary treatment immediately if you notice signs of eye problems. “The sooner you get your dog to the veterinarian, the better,” she says. “Over-the-counter antibiotic ointments are often not strong enough for an eye problem to heal properly.”
Corneal ulceration, also known as ulcerative keratitis, occurs in all breeds of dog, but brachycephalic breeds with pushed-in faces, such as Shih Tzu, Bulldog, French Bulldog, Lhasa Apso, Pekingese, and Pug, are more commonly affected. Age doesn’t seem to play a role in development of corneal ulcers, although most cases occur in young to middle-aged dogs.
“By the time Shih Tzu are old, if they have not had corneal disease, it is because their eyes are healthy,” says Diane Hendrix, D.V.M., DACVO, assistant professor of ophthalmology at the University of Tennessee College of Veterinary Medicine. “Therefore, they have not had the conditions that predispose them to injury as much as younger dogs that develop severe ulcers earlier.”
The Shih Tzu is susceptible to developing corneal ulcers because their eyes are exophthalmic, or protrude due to their large, round shape.
“If untreated, the ulcers can lead to blindness,” says Hendrix, who has studied canine corneal ulcers since 1997. Most recently, she investigated the bacteria that cause ulcers and the concentration of antibiotics used to treat ulcers in the tear film.
HIGHER INCIDENCE OF ULCERATION
The cornea is the transparent layer in the front of the eye that covers the iris, pupil and anterior chamber. When a dog develops a corneal ulcer, it first affects the epithelium, or the protective outer layer of the cornea. The epithelium prevents water and infectious agents from entering the cornea and holds the tear film in place.
Simple ulcers heal quickly with the epithelium repairing the damage, but complications can develop if the ulcer makes its way through to the stroma and becomes infected with bacteria. The stroma is the thickest part of the cornea, and behind it is a thin membrane encasing a single-cell layer known as the endothelium. Enzymes produced by certain bacteria can dissolve the stroma and eventually cause the eye to rupture.
Shih Tzu and other breeds commonly affected with corneal ulcers not only have a higher incidence of ulceration, they also are more likely to have ulcers that become infected. This is partly due to the anatomy of their eyes, the prominent frontal globes, which leaves the cornea more exposed to injury, Hendrix explains.
Corneal ulcers usually result from trauma to the eye. In the case of Stern’s dog, Ledger, he experienced irritation and eventually pustules formed from the rubbing of the abnormal growth of eyelashes, caused by distichiasis, on the cornea. Ulcers also can be related to decreased tear production, eyelid abnormalities or nerve damage.
Tears play an important role in eye health by lubricating the cornea and by helping to fight infection through antibodies contained in tears. Dogs with severe corneal ulcers often experience keratoconjunctivitis sicca, or “dry eye,” which predisposes them to corneal ulcers.
Signs of an ulcer include blinking, squinting or rubbing the eye. Most of the nerves in the cornea are on the surface, so as the ulcer goes deeper into the eye, the pain may lessen though the condition is worsening. Brachycephalic breeds are less likely to show signs of pain than other breeds because their corneal sensitivity tends to be decreased, Hendrix notes.
“This is perhaps the reason that owners miss a very early ulceration of the cornea in these breeds,” she says. “These dogs are less likely to blink and show other signs of discomfort.”
To help prevent eye problems, Hendrix encourages breeders and owners of Shih Tzu and other susceptible breeds to frequently examine eyes for signs of problems. The cornea should look shiny and smooth. Ocular discharge that continues for more than one or two days could indicate a sign of dry eye. A veterinarian can perform a tear test to determine whether a dog has developed dry eye.
Treatment of dry eye involves application of cyclosporine, a local immunosuppressant that is applied topically. A dog may require artificial tears and cyclosporine for the rest of his life to prevent an ulcer from recurring; artificial tears also may be used to prevent the unaffected eye from developing an ulcer.
Ulcers that are diagnosed before they become serious are treated with topical antibiotics, such as eye drops, that are administered several times a day. Other medications may be used to reduce pain and supplement tear production.
DETERMINING TYPE OF BACTERIA
If a veterinarian suspects a dog may have an infected ulcer, he or she is likely to order a cytology examination, which looks for bacteria under a microscope, or culture analysis, which is used to grow bacteria to determine the type of bacteria present. This helps the veterinarian prescribe the best antibiotic treatment. A severe ulcer, one that is deep or perforated, meaning there is a hole in the cornea, may require surgery. A surgical procedure called conjunctival graft is often needed to repair the cornea. The surgery usually costs around $1,000.
An untreated severe ulcer can lead to perforation of the cornea and iris prolapse, or a hole in the cornea with iris tissue protruding from it. Ultimately, a dog may lose his vision and become blind in the affected eye.
Another outcome of severe ulcers is corneal scarring, which is a white spot on the cornea that can alter vision depending on its size and location. The earlier a dog is treated for a corneal ulcer, the less scarring that is likely to occur.
In her research of bacterial keratitis in dogs, Hendrix hopes to learn the most effective therapy to treat corneal ulcers. The Shih Tzu makes up 20 percent of dogs being studied, with Pekingese representing 26 percent.
“I am hoping to learn whether we need to change the therapy that we currently use to treat bacterial keratitis,” she says. “If there is a more effective way to treat ulcers, we hope to learn what it is.”
A recently completed study examined the effectiveness of a topical antibiotic, ciprofloxacin, in treating bacteria contained in the tear film of normal, healthy dogs. “When we treat corneal ulcers in dogs, we want the level of antibiotic to reach and maintain a level that will inhibit growth or kill bacteria,” she says.
“This study looked at how long ciprofloxacin stays at the level needed to kill bacteria that potentially might infect the cornea. We learned that ciprofloxacin levels remain high in tears after topical administration, which may mean that it does not need to be given as frequently as other antibiotics. Of course, the study was done in normal dogs, so dogs with ulcers may have increased tearing, meaning their levels may not be as high.”
In preventing corneal ulcers in dogs, early and aggressive treatment is the best chance for saving the eye. Among the factors that impact prevention are early diagnosis and treatment of dry eye. “If dry eye is treated early with a medication such as cyclosporine and tear production can be increased, then often ulcers will not form,” Hendrix says.
Careful breeding also is important. “Though corneal ulcers are not directly hereditary, certain conformation traits can predispose a dog,” says Hendrix. “Dogs that have excessive protrusion of the eyes are going to be more prone to corneal ulcers. A breeder probably should not breed a bloodline in which every generation develops dry eye or corneal ulcers. Many Shih Tzu do not have eye problems. These are the lines that should be bred.”
The good news is that corneal ulcers can be effectively managed if owners look for signs so treatment can begin early. A dog showing signs of eye disease should be taken to the veterinarian promptly before the condition becomes more serious.
RECOGNIZING SIGNS OF A CORNEAL ULCER
The Shih Tzu, like other brachy-cephalic breeds, is less sensitive to corneal discomfort and thus less likely to show signs of pain. Owners should pay careful attention for these signs of a corneal ulcer:
Rubbing the eye
Eye discharge that continues for more than one or two days
Bloodshot appearance to the eye.
Reprinted with permission from PURINA Pro Club, Shih Tzu Update, July 2007