Photo courtesy of Dr. Kim Downes
Watery ocular (eye) discharge is a common concern of pet owners. Excessive tears drain down the pet’s face, and in time, chronic exposure to moisture produces skin irritation, infection, and odor. The medical term for excessive watering is epiphora which is one of the most difficult conditions to resolve in all veterinary ophthalmology. The fur around the eyes becomes stained reddish brown due to tear pigments called porphyrins, an especially non-cosmetically appealing problem in white-furred pets.
There are two causes of epiphora (excess tearing) in pets: irritation to the eye and abnormal tear drainage.
Irritation to the Eye
One of the eye’s natural responses to irritation is to produce more tears. This helps flush away any irritants that might have contaminated the eye surface.
If your pet is tearing up a lot, squinting, or pawing at their eye, or if the tearing starts suddenly, it's a clear sign they're in pain. Seek veterinary attention right away. Any loss of vision is also an emergency.
Potential Causes
Chronic cases are harder to manage and there are several conditions that may cause runny eyes. Eyes can certainly become chronically irritated from viral conjunctivitis (probably the most common reason for excessive tearing in cats), glaucoma (painful increase in pressure within the eye), reaction to certain eye medications, or, more commonly, from eyelash or eyelid abnormalities.
Some breeds of dogs naturally have hair in their eyes, and this does not irritate in most cases, but in some cases, it can. Hairs can grow from the face at an angle so that they rub against the surface of the eye. Eyelashes can also grow at abnormal angles and rub on the eye. Eyelashes can even grow on the inner surface of the eyelids or corner of the eye and irritate.
Often, magnifying instruments are needed to discover these tiny hairs, and delicate surgical procedures are needed to address them. Complicating the situation, however, is the fact that breeds that tend to have eyelid and eyelash problems also tend to be the same as those with faulty tear drainage anatomy (see below), which makes it hard to determine which of many possible causes is to blame.
Allergy, irritating dust or smog in the air, trauma, or infection can lead to excessive tears from conjunctivitis. These problems, indicated below, are treated medically.
Tear Duct Anatomy
Eye Tear diagram
Eye tear diagram. Graphic by MarVistaVet.
Once we are certain that there is no painful condition, we consider that the eye's drainage ducts may not be normal. The normal eye is most efficient at draining tears.
Your veterinarian will start with a physical exam, and look at your dog’s eyes thoroughly. Looking at the inner corner of the eyelids (the side nearest the nose) one can note the pink, moist caruncle and on the eyelid margins, upper and lower openings called nasolacrimal punctae. These are essentially drainage holes for tears. The punctae are the openings to small passages called canaliculi, which in turn open into the lacrimal sac. The lacrimal sac drains into the nasolacrimal duct, which drains tears into the nasal passages and throat. (This is why we get runny noses and sniffles when we cry and why we can taste our tears when we cry.)
Many problems can occur along this drainage route. One common problem, especially in poodles, bichon frises, and brachycephalic breeds, is simply that the eye socket is shallow. This means that tears overflow from the corner of the eye because the eyelid space there is not deep enough to contain them. These tears never make it to the punctae and instead, spill down the sides of the nose. This condition cannot be repaired; it is simply the conformation of the dog’s face.
Alternatively, the eyelids may be turned inward (a condition called entropion- add link) blocking the puncta and preventing drainage. Another problem may be long hair acting as a wick drawing tears from the eye to the skin, especially in breeds where hairs grow on the caruncle. This hair may be kept trimmed; though, if the hair is part of the nasal skin fold of a brachycephalic breed, surgery may be needed to remove or alter the skin fold.
Diagnosis
It is fairly easy to determine if there is a problem with drainage in a non-invasive way, which is sometimes called the Jones test. A stain for eyes called fluorescein is dropped onto the eye, and if the tear drainage system is intact, the dye should be evident at the nostrils after a couple of minutes.
At a minimum, a Schirmer tear test (STT), corneal fluorescein staining (dying the cornea so your veterinarian can see any defects), and tonometry (checking eye pressure) is recommended. If the tear level is excessive, there is most likely an underlying condition causing excessive tears. If the STT is normal, there may be an underlying problem with tear flow due to something about the dear duct structure. A test called tear break-up time may also be recommended to see if tears lack the right makeup (yes, tears are made of multiple substances).
Treatment
Flushing
Old infections or injuries may cause enough scarring to close the punctae, canaliculi, or nasolacrimal ducts. Sometimes vigorous flushing of saline through the ducts, performed under general anesthesia, can re-open them and help work toward a diagnosis as well (if there was a clog). Sometimes the puncta are congenitally closed (present at birth; common in poodles and cocker spaniels) and can be surgically re-opened. Medications may be prescribed after a flushing procedure as well.
Surgery
Surgery to reopen drainage is a procedure that not all veterinarians are comfortable performing. Discuss with your veterinarian whether a referral to a specialist would be best for you and your pet. In this case, special equipment is needed. Ask your veterinarian for a referral if needed.
Addressing The Staining
An assortment of remedies has been suggested to resolve the unsightly reddish stains that result from chronic tear drainage. The following are some comments on suggestions we have heard.
Low Doses Of Tetracycline Or Tylosin
Variable success has been reported but the problem is that using antibiotics in this way constitutes less than responsible use of antibiotics, and resistant bacterial strains may result from this practice. It is generally frowned upon by pharmacologists. Furthermore, tetracycline should not be used in immature animals as it will cause teeth to stain.
Topical Therapies
Treating the main problem behind the watery eyes, like inflammation and/or infection, corneal ulcers, calcium buildup, or other eye conditions, can also stop the excessive tearing. Your veterinarian may recommend prescription eye drops or lubricants to soothe mild eye irritation and help with tear film issues. If watery eyes are caused by allergies, antihistamine eye drops might help.
If your pet needs more specialized attention, your veterinarian may refer you to a veterinary ophthalmologist for further care.