Tears are necessary for the health of the eye. They provide moisture, wash away irritants, and help nourish the cornea. Tears are produced by two glands within the eye socket; the lacrimal gland which is located above the eye produces a majority of the tears while the gland within the third eyelid makes up the remainder. If something interferes with normal tear production, the eye becomes dry and this is referred to as Keratoconjunctivitis Sicca, or KCS. It is commonly called “Dry Eye” and is an uncommon but treatable eye disease in dogs.
Eye Disease in Dogs: Causes and Diagnosis of Keratoconjunctivitis Sicca
Anything that damages the tear-producing glands can result in KCS. Removal of the gland of the third eyelid, which may occur during cherry eye surgery, can result in dry eye. Sulfa-type antibiotics can also cause it. The most common cause is immune-mediated destruction of the lacrimal gland. The dog’s own immune system attacks the gland and the result is a gland which doesn’t work.
Affected eyes appear dry and dull with red and inflamed conjunctiva. Other glands within the eyes produce excess mucus in reaction to the lack of moisture which results in a thick yellow eye discharge. The discharge may turn green if an infection is present as well. If left untreated, dry eye eventually leads to blindness due to brown pigment which is deposited on the cornea.
Diagnosis is relatively easy using a Schirmer tear test. A specially designed strip of paper is inserted into the corner of the eye beneath the eyelid which measures the amount of tears needed to wet the paper in one minute.
Eye Disease in Dogs: Treatment of Keratoconjunctivitis Sicca
Artificial tears can be used but must be administered frequently, at least six times a day. This is not practical for most dog owners and therefore rarely effective. Given that the most common cause of KCS is immune destruction of the lacrimal gland, the most effective treatment involves suppressing the immune system at the level of the eye. This can be done with one of two immunomodulating drugs, cyclosporine or Tacrolimus. Both drugs are administered as eye drops, given once or twice a day, which if effective, cause an increase in the tear production within a few weeks. In cases where the immunosuppressive drugs are ineffective, a surgical correction may be tried. The surgery is called a parotid duct transposition and should only be performed by a veterinary ophthalmologist. The parotid salivary gland provides saliva to the mouth. In this surgery, the duct is moved from the mouth to the eye. Every time the dog salivates, saliva is delivered to the eye providing moisture. There are some side effects from this surgery including mineral deposits forming on the surface of the cornea, and excessive tearing while the dog is eating.
If your dog exhibits signs of dry eye, see your veterinarian immediately. The sooner treatment is started, the better your dogs prognosis for vision will be.
To learn about eyelid diseases in dogs, click here.
To learn about cataracts in dogs, click here.
To learn about glaucoma in dogs, click here.