You see commercials on television for “Dry Eye” in humans. Did you know that dogs can get “Dry Eye” too?
The formal name for “Dry Eye” is Keratoconjunctivitis sicca, or KCS. Dry Eye happens when there is not enough tear film over the surface of the eye and the lining of the lids. The result is severe drying and inflammation of the cornea (which is the transparent front part of the eye) and conjunctiva (the clear membrane that covers the sclera, the white part of the eye).
This condition is relatively common in dogs, particularly cocker spaniels, bulldogs, West Highland Terriers, Lhasa Apsos, and Shih-Tzus. Female dogs may be more predisposed to KCS than male dogs.
What does Dry Eye look like?
- Excessive blinking
- Swollen, red (conjunctival) blood vessels
- Swelling of the tissue that lines the eyelids and surface of the eye (chemises)
- Prominent third eyelid (nictitans)
- Discharge of mucus or pus from the eye
- Corneal changes-pigmentation and ulceration
- The eye looks dull instead of shiny and moist
- Severe disease can lead to impaired or complete loss of vision
- Often a dry nose on the same side as the dry eyes
What Causes It?
- The body’s own immune system is the most common cause of Dry Eye. Inflammation of the gland that produces tears is brought about by abnormal activity of the body's immune system attacking the gland. Immune-mediated Dry Eye is often seen with other immune-mediated diseases
- Congenital (hereditary) in Pugs, Yorkshire Terriers, and a few other breeds
- Nerve damage after proptosis (eyes displaced from their sockets) or after a disease that interrupts the nerves of the tear gland
- Drug induced; sometimes general anesthesia and atropine cause temporary dry eye
- Drug toxicity; some sulfa-containing drugs or Etodolac (an NSAID) may cause a temporary or (sometimes) a permanent condition
- Removal of the third eyelid, sometimes done as a treatment for “cherry eye”, may lead to this condition especially in at-risk breeds.
- X-Ray induced; can occur in response to the eye coming into close contact with a primary beam from a radiology device.
- Canine distemper virus
- Certain bacteria (Chlamydia)
- Long term conjunctivitis (inflammation) of the conjunctiva (lining of the eyeball and lids) and eyelids
How Can We Tell if Your Dog has Dry Eye
In addition to a physical and ophthalmological exam on your dog, a simple test called Schirmer tear test can be done to measure the amount of wetness on the eye. These small strips measure the amount of tear production that is taking place in the tear ducts. A low value means keratoconjunctivitis sicca.
A fluorescein stain, a non-invasive dye that shows details of the eye under black light, can be used to check for abrasions or ulcerations on the cornea secondary to the lack of tear production. Your doctor may also want to do a culture of the eye discharge to check for infection.
How Do We Treat Dry Eye?
The main treatment is a topical medication just like humans use (Restasis, Cyclosporine, Tacrolimus) to reduce the activity of the patient’s immune system and help control the inflammation. These medications do not just moisturize the eye. They actually help the patient produce more tears.
You will need to be sure to clean your dog's eyes before you administer the medication, along with keeping the eyes clean and free of dried discharge. Your veterinarian may prescribe an artificial-tear medication and possibly a lubricant to help with keeping the eye moist. Your veterinarian may also prescribe a topical ophthalmic antibiotic either to treat a bacterial infection or as a preventative.
Some patients with KCS are predisposed to severe corneal ulceration, so you will need to call your veterinarian at once if the pain increases so that it can be treated before serious injury occurs. Ulcers on the cornea require different medication and can become very serious.
A surgical procedure called parotid duct transposition may be used to reroute the salivary duct so that it lubricates the eye. Saliva can be used to compensate for the lack of tears, delivering fluid to the inferior conjunctival cul-de-sac. It’s performed much less frequently since cyclosporine was introduced. Saliva can be irritating to the cornea. Some patients are uncomfortable after surgery and require ongoing medical therapy.
Living and Management
Immune-mediated causes of Dry Eye usually require life-long treatment. This means your dog will be on medication life-long. Regular office visits are required for your dog to ensure proper treatment. Your veterinarian will want to recheck your pet at regular intervals to monitor response and progress. The Schirmer tear test will probably be performed again four to six weeks after initiating cyclosporine to evaluate response. The test is normally performed every 6 months thereafter or sooner if there are any issues. Often, medication strength and dosage may need to be adjusted to keep your pet comfortable and healthy.
Other types of disease that cause Dry Eye may be temporary and may require treatment only until tear production returns. Your veterinarian will be able to determine if your dog may only need to be medicated temporarily.