Keratoconjunctivitis Sicca (KCS, Dry Eye) in Dogs
Disease that Appear Similar to Dry Eye in Dogs
Several eye diseases may resemble keratoconjunctivitis sicca. It is important that an accurate diagnosis is made early in the disease because chronic KCS may lead to blindness. Diseases that can appear similar to KCS include: Conjunctivitis. This is a syndrome associated with inflammation of the tissues that line the eyelids and cover the eye. It is sometimes called “pink eye.” Clinical signs of conjunctivitis include increased tearing, discharge, redness and sometimes squinting. There are many causes for conjunctivitis. See the Client Education article on Conjunctivitis. Episclerokeratitis. This is an inflammation of the cornea and sclera (the white outer shell of the eye). This disease is much less common than KCS. The inflammation causes swelling and thickening of the tissues that line the eye. See the Client Education article on Episcleritis for more information. Dacryocystitis. This is an inflammation and infection of the tear drainage system. There is often a large amount of yellow-green discharge from the affected eye and there may or may not be pain associated with this disease. Discharge often accumulates in the inner corner of the eye and continues even after cleaning. Tear production is normal in this disease; the problem lies in the ducts that drain the tears away from the eye. Corneal ulceration. An abrasion of the cornea causes discharge and redness of the eye. The onset is usually acute and the eye is painful. A corneal ulcer is diagnosed by applying fluorescein stain to the eye. The eye only takes up stain if ulceration is present. Corneal ulcerations may also occur as a result of KCS, especially shortly after the onset of KCS. It is important that the tear production is measured when a corneal ulcer is present. See the Client Education article on Corneal Ulcers. Pannus. This is an immune-mediated disease of the cornea that only mildly resembles KCS clinically. A progressive inflammation and pigmentation is present in the cornea that usually starts in the outer corner of the cornea and slowly progresses over the cornea towards the inner corner. This disease is most commonly seen in German shepherd dogs (GSD) and GSD-cross dogs. Tear production is normal in this disease. See the Client Education article on Pannus. Pigmentary keratitis. Pigment invades the cornea of certain breeds of dogs with very prominent, exposed eyes. This pigment occurs mainly in the area of the cornea closest to the nose, and is common in the pug, shih tzu, Lhasa apso, and Pekingese. Tear production is normal in this condition.
Veterinary care includes diagnostic tests and subsequent treatment recommendations.
Diagnosis In-depth for Dogs with Keratoconjunctivitis
It is important to inform your veterinarian of all the medications your dog is currently taking because KCS may be an uncommon side effect associated with some medications. Diagnosis often includes the following: Examination of the eye including a thorough evaluation of the eyelids, conjunctiva and cornea. Schirmer Tear Test. This test measures tear production. Normal tear production is usually more than 15 mm/min. Caution should be used when interpreting this test. If another disease is present that increases the tear production, the Schirmer Tear Test may reveal borderline normal values, masking the KCS. Alternatively, some conditions also falsely lower the results. For these reasons, the test may be repeated several times before a definite diagnosis of KCS is reached. Fluorescein stain. The dye is applied to the cornea to check for the presence of a corneal ulcer. Culture of discharge. A culture may be submitted if a secondary bacterial infection is suspected. Routine blood work. Your veterinarian may recommend blood tests including a complete blood count, serum biochemistry profile and thyroid hormone assays if an underlying disease is suspected.
Treatment In-depth for Dogs with Keratoconjunctivitis
Treatment is aimed at increasing tear production, applying artificial tears, and reducing any bacterial infections, and decreasing inflammation and scarring of the cornea. When using eye medications, be sure to ask your veterinarian whether the medications can be administered at the same time, or whether they should be separated by several minutes. Some medications can be administered together; others need to be administered alone. In general, drops are applied prior to ointments and no more than two medications are given together at one time. Application of 0.2% cyclosporine ointment is designed to increase tear production. This product is most effective in increasing tear production if some residual tear production is still present. It is less effective in dogs that have no tear production prior to starting this medication. When used on a long-term basis, this medication may also help to decrease some of the pigmentation that is commonly present on the cornea in chronic KCS. It is usually applied twice daily, and it must be used on a continual basis for the rest of the dog’s life. There are times when this product is not available, and it is necessary to obtain a solution of cyclosporine from a licensed compounding pharmacy. Pilocarpine drops given by mouth are occasionally tried to increase tear production, but they are not very successful. They may taste bitter to the dog, and may also induce vomiting and diarrhea if given in excessive amounts. In moderate to severe cases of KCS, artificial tear solutions and ointments are used in addition to cyclosporine. Drops provide moisture and ointment provides lubrication to the surface of the eye. They are particularly important in the early stages of treatment, because it may take several weeks for the cyclosporine to increase the tear production. They are also important when tear production does not return to normal with cyclosporine therapy. Antibiotic drops or ointment may be used if a secondary bacterial infection is present. Corticosteroid drops or ointment may be used to decrease inflammation. These medications are only used after fluorescein staining of the cornea has determined that there is no ulceration present. Corticosteroids cannot be used in the presence of a corneal ulcer because they delay healing. In severe cases of KCS that do not respond to medications, surgery may be performed in which a salivary duct is moved from the mouth to the eye. This results in saliva flowing over the eye to keep the eye moist. It is not an ideal treatment for KCS because saliva is not the same as tears, and the flow of saliva cannot be controlled very well. The surgery is helpful, however, for those dogs that remain persistently painful and squinty despite trying all forms of medical therapy.