Dry eye is a condition that affects the tear glands of dogs, cats, and humans. Left untreated, dry eye can cause serious discomfort and damage to the eye. Fortunately, treatment options are available in most cases.
What is Dry Eye in Dogs?
Dry eye is an ocular condition where the tear glands do not produce enough tears to lubricate and protect the eye. This causes dryness and inflammation of the eye that can lead to infection. Dry eye is formally known as keratoconjunctivitis sicca or KCS. The word "kerato" refers to the cornea, a clear covering on the eye. Conjunctivitis means inflammation of the thin membrane that coats the eye and eyelid. The term "sicca" means dry.
In a normal eye, there are lacrimal glands (tear glands) located above the eye and in the third eyelid, found in the lower inner corner of the eye. Normally, functioning lacrimal glands produce tears that contain water, salts, oil, and mucus. Tears keep the eyes lubricated and flush out material from the eyes that can cause irritation and infection.
Without proper tear production, the eye can become injured by particles of debris and even become infected. The cornea becomes thickened in an effort to protect the rest of the eye from injury. The tear glands may still produce oil and mucus, but not water. This can leave a thick discharge in and around the eyes.
Signs of Dry Eye in Dogs
- Thick eye discharge (often looks like yellow or green mucus, pus, or crusting)
- Eye redness/conjunctivitis
- Excessive blinking/blepharospasms
- Dry appearance to the eye (no sheen on the eye)
- Discoloration or pigmentation on the surface of the eye
- Corneal ulcers
Causes of Dry Eye in Dogs
Dry eye is most commonly caused by an immune-mediated disease process that damages the tear glands. This can occur in any dog but is especially common in American Cocker Spaniels, Bulldogs, Miniature Schnauzers, Shih Tzus, and West Highland White Terriers.
Other potential causes of KCS in dogs include the following:
- Congenital disorders: lacrimal glands are absent or do not function properly at birth
- Infectious diseases, especially those that affect the upper respiratory system
- Cherry eye (prolapse of the third eyelid)
- Some endocrine diseases
- Trauma or damage to the eye (caused by injury, toxicity, or disease processes)
How Vets Diagnose Dry Eye in Dogs
It is important to contact your veterinarian at the first sign of eye problems. Diseases of the eye can progress rapidly. The sooner your vet can make a diagnosis, the better the chances of effective treatment.
Your vet will perform a thorough examination of your dog's eyes followed by some special eye tests. The first test is typically the Schirmer Tear Test. A small, specially treated paper strip is inserted under the lower eyelid and held in place for one minute. The paper will become moistened by tears and the liquid will reach a certain point on the strip. Normal tear production should reach the 15mm line or beyond. 5mm or less indicates severe dryness. Results of 11-14mm are borderline and may reveal early dry eye.
Next, your vet may want to perform a fluorescein stain test on the eye to check for damage to the cornea. A harmless fluorescent dye is dropped into the eye and rinsed with saline. Then, a light is used to see if the stain was retained on the cornea. If ulcers, lesions, or scratches are present, they will uptake stain. This is an important test because KCS can cause corneal ulcers and injuries that require special medication to heal.
Treatment for Dry Eye in Dogs
Once your dog has been diagnosed with KCS, your vet will recommend beginning treatment right away. Treatment will involve the use of one or more kinds of topical eye medications.
Cyclosporine and tacrolimus are immunosuppressive drugs that treat immune-mediated KCS. Your vet will likely prescribe one of these medications if immune-mediated KCS is suspected. These come in ointment or drop form and need to be administered one to three times daily.
Topical antibiotic and/or steroid medication may also be needed in the eyes. Antibiotics can treat or prevent infections. Steroids reduce inflammation.
Artificial tears can be helpful to lubricate the eyes, but they must be used frequently to be effective. These alone will not actually treat KCS, although they may be used in conjunction with other eye medications.
Be sure to follow your vet's recommendations regarding treatment and follow-up exams. It is important for your vet to recheck your dog's eyes regularly to monitor the response to treatment and the progression of the dry eye.
Surgery may be necessary in severe cases that do not respond to medical treatment. A veterinary ophthalmologist can perform a surgical procedure called a parotid duct transposition. This involves re-routing one of the salivary ducts to the eye so that the saliva can provide lubrication. Saliva can work well as a tear substitute, but other complications may occur, such as mineralization of the cornea and excessive eye-watering when food is present.