What Is Keratoconjunctivitis Sicca and How Does It Affect Dogs?

If you notice a mucus discharge in your dog's eye, you may wonder how you can tell if it is conjunctivitis or keratoconjunctivitis sicca (also known as dry eye). Conjunctivitis is caused by an inflammation of the eye, and the dog's eye will usually have a red or pink appearance (hence the alternative name, pink eye).

On the other hand, keratoconjunctivitis sicca is caused by insufficient tear production by the tear glands. Regardless of the cause, if your dog's eyes appear red and/or there is a mucous discharge, you need to take him to the vet immediately. Left untreated, diseases such as keratoconjunctivitis sicca may cause blindness.

In this exclusive interview, pet parent and veterinarian Dr. Cathy Alinovi shares what she has learned about dry eye, or keratoconjunctivitis, from her patients.

Dr. Cathy: That big fancy word means dry eye. Sicca means dry. Kerato means having to do with the cornea (the clear part of the eye that we see through), conjunctiva means the eyelids, and itis means inflammation.

Dr. Cathy: If the eyes do not make enough tears, they become dry. Tears are meant to moisturize the surface of the eye. Tears bring nutrients; tears wash away dirt.

Tears have three parts: water, fat and mucus. The fatty, lipid layer of tears helps hold the outer surface of the tears together. The water layer is where all the good nutrients are carried. The inner mucus layer is the part that makes the tears adhere to the eyeball itself.

Think of it like a sandwich on the eyeball: mucus, water, and fat. A problem with any layer of the sandwich can lead to dry eye, although not enough of the water portion is the most common cause in dogs.

If there is not enough fat, the tears leak out and drain on the face. If there is not enough water, the eye film is gooey. If there is not enough mucus, the tears do not stay on the eyeball.

Most causes of dry eye are immune related, for instance:

• Allergies
• Autoimmune disease
• Viruses
• Sun damage to the glands
• Nerve damage

Additionally, dry eye is a very common side effect of many medications, especially sulfa drugs.

Dr. Cathy: When not enough tears are produced, the eyes become dry and dirty. In addition, they can develop an infection. Infection can lead to corneal ulcers, which can be very painful. Once the ulcer heals, there may be scarring that can be hard to see through.

Dr. Cathy: If it goes untreated long enough, it is very possible your dog will go blind.

Dr. Cathy: The most common symptoms of dry eye are:

• Red eye
• Swollen eyelid
• Squinting
• Tearing
• Eye boogers (progressing to white cloudiness on the eyeball)
• Pigment on the eyeball
• Third eyelid up
• Sunken eye due to pain

Dr. Cathy: Dry eye tends to affect cute, little dogs with big eyes that tend to bulge. See the table below for specific examples. (Table is arranged according to the AKC classification for each breed.)

Dr. Cathy: In my opinion, there does not seem to be gender susceptibility.

Dr. Cathy: One type of KCS, neurogenic KCS, is caused by damage to the facial nerve, which is a nerve that helps move the muscles of the face. If the dog had some kind of facial trauma that involved the facial nerve, he may have dry eye as that nerve branch stimulates tears. Other injuries include cherry eye damaging the third eyelid, which makes sixty percent of the tears, and excessive rubbing, perhaps from allergies.

Dr. Cathy: It is diagnosed with a quick in-office test called the Schirmer Tear Test. A tiny, sterile strip of paper is placed on the edge of the eyeball to soak up the liquid of the tears. The amount of moisture soaked up by the piece of paper in 15 seconds determines if your dog has dry eye. In other words, if there is not enough liquid on the paper, the diagnosis is KCS/dry eye.

Dr. Cathy: Side effects are uncommon but occasionally a dog will experience vomiting or diarrhea. The biggest side effect is for the owner because some dogs need the medication dropped into the eye three or four times a day. It can be tough to juggle the rest of one's life with the need to apply eye medications that often.

Dr. Cathy: Because most causes of dry eye are related to the immune system, the most common medications affect the immune system.

Cyclosporine and tacrolimus are two very commonly used medications that are administered in the eye once or twice daily to help increase tear production.

Some dogs benefit by treating their allergies with allergy desensitization shots. Other dogs are treated by removing dry dog food from their diets.

Dr. Cathy: Topical medication is an easy outpatient treatment that can be continued at home. Most dogs are good patients for medical treatment.

Dr. Cathy: It depends on the cause of the dry eye. For the dogs that are fortunate and only need a food change, the eyes will improve quickly and treatment will not need to continue. For those dogs with less clear causes of the dry eye, treatment is necessary for life to protect the eyes.

Dr. Cathy: If left untreated, the dog may suffer in a range of mild discomfort to severe pain, depending on the acuteness of symptoms. Dogs that are treated enjoy an excellent quality of life.

Dr. Cathy: The surgical treatment option is a really cool surgery (in my opinion, anyway), in which the duct (or tube) from a salivary gland is rerouted to the eye to provide moisture. I suspect these dogs have extra tears when they are hungry though; otherwise, there are minimal side effects and you do not have to medicate daily.

Dr. Cathy: Make sure the eyes stay moist.

To wrap this all up for pet parents, with the proper diagnosis and prompt medical attention, keratoconjunctivitis sicca, or dry eye as it is more commonly referred to, is a treatable health condition that offers little danger for your beloved pet. However, as mentioned earlier, if left untreated, it can result in blindness. The safest choice for your pet is to always err on the side of caution and obtain a professional opinion from your veterinarian about your pet's health issues.