Proactive Breeders Improve Outcomes for Dogs with Ocular Diseases
Experience can be helpful when it comes to recognizing and managing ocular diseases in Shih Tzus. Just ask Lila Pontius of D'Lilas Shih Tzu in Bunnell, Fla. After 10 years as a breeder, she has seen enough to know readily when her dogs are not seeing all they should be.
When Pontius took "Tango," a 13-year-old male, to the veterinarian late last year, the breeder was gravely concerned. She'd cared for the dog through melanoma and a related surgery to remove part of his jaw in early 2009. By the end of last year, Tango was holding his right eye closed and was clearly in pain. He wouldn't follow her around the house anymore, preferring only to lie on his dog bed.
"Our veterinarian determined Tango had a type of corneal ulcer that is common in older dogs," Pontius says. "I was afraid he would have to have his eye removed, but the veterinarian was able to debride, or scrape away the old tissue, on Tango's corneal epilthelium."
It took more than four months of once- to twice-weekly visits to the veterinarian, three debridements, and application of an ointment to Tango's eye every four hours, including at night, to resolve the issue. "To put the medicine in his eyes was challenging," Pontius says. "He was in so much pain, and resisted every time we tried to apply the ointment to his eye. He became less resistant over time, and we knew he was feeling better."
According to experts, brachycephalic breeds like the Shih Tzu, with their broad, short faces, are more susceptible to corneal ulcers, partly because of their prominent eyes. "Ulcers are commonly caused by trauma to the corneal surface, whether from an external source or self-inflicted," says Kathleen Barrie, D.V.M., DACVO, professor of comparative ophthalmology at the University of Florida College of Veterinary Medicine.
"Unfortunately, Shih Tzus often need to be seen in a hospital for corneal ulcers. Their corneal sensitivity is lower than the average dog, so a breeder may not know the Shih Tzu has an ulcer until it becomes much more serious. Any ulcer in a Shih Tzu should never be taken lightly. If an ulcer goes untreated, it can lead to rupture of the cornea and loss of vision. It is always considered serious until proven otherwise. Identifying the cause of the ulcer or any contributing factors such as distichiasis, or extra eyelashes, or a poor blink response requires a thorough ocular exam."
Depending on severity, treatment may be necessary with a variety of topical and systemic medications, such as an anti-inflammatory, analgesic or antibiotic. "In severe or progressive cases, reconstructive surgery, including grafting procedures, may be needed," says Cecil Moore, D.V.M., DACVO, professor of ophthalmology at the University of Missouri College of Veterinary Medicine. "If left untreated, the consequences could be severe tissue scarring, loss of vision, shrinkage and possibly removal of the eye."
Distichiasis & Dry Eye Pontius also went through eye problems with "Daisy," an 11-year-old companion dog. A few years ago the Shih Tzu suffered from distichiasis, a condition in which an extra row of eyelashes grows out of the base of the meibomian gland, the oil gland on the eyelid margin. Taking her veterinarian's advice, she let Daisy's condition resolve itself, which it did in a few weeks. However, not all dogs experience such a relatively mild degree of distichiasis.
According to the Canine Eye Registration Foundation (CERF), approximately 20 percent of Shih Tzus screened for eye diseases are affected with distichiasis. Depending on the size, location and number of distichia, these extra eyelashes may not be visible by direct inspection. A veterinarian or veterinary specialist uses magnification combined with a bright focal light source, such as a slit-lamp biomicroscope, to evaluate distichia.
"A few extra eyelashes may not cause any ocular disease," Barrie says, "yet one very stiff distichia directed toward the cornea can cause inflammation, known as chronic keratitis, and ulcerations."
Signs of distichiasis vary, ranging from asymptomatic cases to those involving mild tearing and mucus accumulation. Severe signs are marked squinting and pain associated with a corneal ulcer. Disease management includes prescriptive ointments or, in serious cases, surgical removal of the extra row of eyelashes through electroepilation (electric current) or cryoepilation (freezing).
"For the surgical options, sedation or anesthesia is needed," Moore says. "Since specialized equipment, such as a surgical microscope, may also be needed, it is best to seek treatment from a veterinary specialist. If this condition is not treated, it can result in pain and a persistent or recurrent corneal ulceration."
After overcoming distichiasis, Daisy developed a cyst on the underside of her right eyelid. The cyst was removed, but this caused dry eye. "Surgery to remove the cyst interfered with the tear gland and resulted in Daisy's right eye not producing enough tears," Pontius says. "Now, I routinely administer lubricating drops to her eye and carefully monitor her eye. If I see her eye is getting red or is running, or if she is squinting or holding her eye closed, I take her to the veterinarian right away."
Dry eye, or keratoconjunctivitis sicca (KCS), is believed to affect about 1 percent of Shih Tzus. Though the breed is not considered at high risk for dry eye, anatomy plays a role. "Predisposition in pug-nosed or brachycephalic dogs is felt to be related largely to their relatively exposed eyes," says Moore. "They require more tear secretions to coat such prominent eyes."
Dry eye stems from insufficient production of the aqueous portion of the tear film. This part of tears is produced by the lacrimal (tear) gland and the gland of the third eyelid, which dogs have as extra protection for the surface of the eye. Lack of tears causes a drying out of the eye's surface structures. This can lead to ocular pain, corneal ulcerations, chronic keratitis and chronic conjunctivitis, which is swelling and infection of the membrane lining the eyelids (conjunctiva). Dry eye can eventually lead to loss of vision.
Dry eye also can be caused by certain prescription drugs, acute or chronic infections, hormonal abnormalities (hypothyroidism) or systemic disease. Applying lubricating drops to the eye can help prevent signs of dry eye. Selective breeding for dogs with good eyelid and facial conformation, such as good ability to blink effectively, is important in reducing the incidence of dry eye. Early surgical correction of third eyelid gland prolapses, removal of chronic irritants, such as abnormal hairs, and avoidance of certain medications can also help avoid development of dry eye.
If there is evidence of chronic keratitis, ulcerations or poor blink response, surgery can be performed to help prevent further exposure. "The procedure used at the University of Florida is a modified medial canthoplasty," Barrie says. "This not only cuts down on exposure, but can rid the dog of aberrant hairs often seen in the medial canthus, or corners of the eyes."
Tear Staining & Entropion Carlene Snyder, chairwoman of the American Shih Tzu Club's Health, Education and Research Committee, has bred one litter of Shih Tzu puppies under the Carling prefix nearly every year for three decades. Like Pontius, she has experienced tear staining and says regular grooming can be helpful.
"I had been involved in Cocker Spaniels and Poodles before Shih Tzus, and when I got started with the breed, I didn't realize how much work was involved in keeping Shih Tzus' faces clean," Snyder says. "For those who exhibit at dog shows, a Shih Tzu's face requires daily cleaning. I advise people who own Shih Tzus as companions to keep the dog's facial hair cut in a 'puppy cut,' so there is not as much hair to possibly irritate the dog's eyes and cause more tears."
Tear staining, also known as epiphora, may be due to excessive tearing or a problem with drainage from the eye. Tear staining is most noticeable in dogs with white facial hair. Innate pigments in tear fluid darken the hair around the eye, thus it is highly visible contrasted against the dog's white hair.
"Tear staining is often a major concern for show dogs because of the unsightly appearance, but it can also indicate lid abnormalities or ocular disease," says Barrie. "A small amount of tear staining is normal, but in brachycephalic breeds, it can indicate an anatomical defect."
Among the anatomical defects that could cause tear staining are medial entropion, or the rolling in of the inside corner of the lid; hairy caruncle, or abnormal hair follicles at the base of the third lid; or a lack of an opening, known as atresia of lacrimal puncta. If tear staining is severe or if there is corneal disease associated with the condition, surgical correction is recommended.
Entropion is an eye disorder that affects about 5 percent of Shih Tzus. Most cases are due to a dog's facial and eyelid conformation. Signs of mild entropion include excessive tearing, squinting, redness and facial rubbing. In more severe cases, there can be irritation of the cornea that produces keratitis or ulceration.
"Surgery is the definitive method in treatment of entropion," Moore says. "Breeders should discuss the matter with their primary care veterinarian who, when appropriate, may consult or refer to a specialist. In general, because of concerns about a number of possible heritable conditions, I would emphasize the importance of screening all breeding animals for genetic eye diseases by a board-certified veterinary ophthalmologist."
Having consulted a veterinary ophthalmologist for Daisy and Tango, Pontius says both have fared well, regaining strong ocular health and resuming their normal behaviors. "Daisy's eyes look good, though I stay alert for signs of difficulty," she says. "Tango's problems also are resolved, and he is back to following me all around the house. Looking at his eyes, you wouldn't be able to tell he ever had any trouble."
Purina appreciates the support of the American Shih Tzu Club and particularly Carlene Synder, chairwoman of the Health, Education and Research Committee, in helping to identify topics for the Purina Pro Club Shih Tzu Update newsletter.