In a healthy eye, a watery film of tears coats the eye’s surface, called the cornea. The tear film protects the cornea and lubricates the eyelids. Dry eye, also known as keratoconjunctivitis sicca (KCS), occurs when the tear glands don’t produce enough tears and the cornea becomes dry. KCS may affect one or both eyes.
Risk factors and detection
Dry eye is common in dogs. Certain dog breeds, including cocker spaniels, bulldogs, West Highland white terriers, Lhasa apsos, and Shih Tzus, are particularly susceptible. The most common cause of dry eye is destruction of the tear glands by the body’s immune system. Trauma, certain drugs, and illness also cause dry eye.
Signs of dry eye include:
- redness of the tissues surrounding the eye (conjunctivitis)
- thick, stringy, yellow or green mucus in and around the eye
- a dull appearance to the eye’s surface
- squinting or refusal to open the eye
- swelling of the tissues around the eye.
Because the tear film protects the cornea, a dry eye can lead to corneal ulcers or infection. If left untreated, the condition can result in blindness from corneal scarring.
When checking your dog for dry eye, your veterinarian will conduct a
Schirmer tear test, a simple, pain-free test that measures tear production. The doctor will place a strip of filter paper under the lower eyelid and hold it there for one minute. Your veterinarian may also check for corneal ulcers using a special eye stain or recommend additional tests if he or she suspects other disease.
Treatment
The goal of treatment is to keep the cornea moist. You can do so by giving your dog drugs that stimulate the tear glands to produce more tears or by applying artificial tears.
Cyclosporine, an immunosuppressive drug incorporated into an eye ointment, reduces the destruction of the tear glands by the body’s immune system and stimulates tear production. You’ll apply the ointment once or twice daily, depending on the dog’s response. Cyclosporine boosts tear production as long as there is enough tear gland left to respond. Treatment with this drug is life-long. Interrupting treatment for as little as 24 hours causes symptoms to return in most dogs.
Pilocarpine, an older drug widely used before the development of cyclosporine, directly stimulates the tear glands. Pilocarpine is available as a liquid to be added to food or as an eye ointment. Cyclosporine is the preferred treatment because dogs develop a tolerance to pilocarpine and can experience such side effects as vomiting and diarrhea.
If your dog doesn’t respond to cyclosporine or pilocarpine, you’ll need to apply artificial tears throughout the day. Most owners find this treatment inconvenient.
Another less common treatment involves rerouting a salivary gland to the eye. The surgery, called parotid duct transposition, is a last resort. Saliva can irritate the eye, and heavy salivation can cause a watery eye and constantly wet face.
Your veterinarian may also prescribe other medications for your dog, such as topical antibiotic ointments, corticosteroids, or mucolytic agents, which help break down thick mucus. Your dog may need multiple treatments daily. Also keep her face clean by removing excess mucus and crusts with a damp cotton ball.
