Dry Eye--KCS

Princess, a nine year old Shih Tzu, sat on the exam table peering at me through the little gaps where her eyelids weren’t stuck together with a thick green goo. Her owner was used to clearing a little discharge every day, but this stuff was like super glue on her hairy little face, and no amount of washing was enough to get rid of it

All that green discharge looked like the worst case of pink eye on record, but in this case Princess did not have an infection, she had a condition called Keratoconjunctivitis Sicca (you have got to love those monstrous medical terms) or KCS for short. Dogs with KCS are not producing the liquid component of their tears, so the mucous producing glands go into overdrive trying to get something to cover the surface of the eye and protect it. The result is a very dry, irritated eye with a sticky mess around the eyelids.

We diagnosed the problem by folding over the top edge of some little paper strips that are marked in millimeters and hanging them off the lower eyelid for one minute. The paper wicks the tears from the surface of the eye and the distance that the moisture travels down the paper in 60 seconds lets us know how much tear production there is. A normal distance is somewhere in the neighborhood of 20mm. Princess had a tear production measurement of 0.

The most common reason the tear glands stop producing the liquid portion of the tears is that the immune system, usually for unknown reasons, has gotten confused and has taken it upon itself to start attacking them. Sometimes KCS develops as an adverse reaction to certain antibiotics, and sometimes it is the result of a malfunction in the nerves that carry the signals to stimulate tear production. Nerve related KCS often affects only one side and it also tends to cause dryness in one nostril and reduced salivation on the affected side as well. Middle aged members of breeds with short noses and prominent eyes are the ones most commonly affected by immune mediated KCS, but any breed can develop the problem.

Back in the bad old days veterinarians used to fix cherry eye, a condition in puppies where a tear gland in the inside corner of the eye flips up and protrudes above the lower eyelid, by picking up the gland with some forceps and snipping it off while the patient was anesthetized. It was quick and easy and the problem was solved on a permanent basis. In time it was found that after you remove a vital component of the tear making apparatus your patient will start having problems as his natural tear production wanes with age. That is what we call iatrogenic (which is a word that sounds so much fancier than "doctor induced") KCS. These days we repair cherry eyes by tucking the gland back into its proper place so it can continue to function for the life of the patient.

There are not a lot of good options for treatment of nerve related or iatrogenic KCS, although some cases may be candidates for a complex surgery that transfers the opening of a salivary gland into the eyelid. Fortunately the vast majority of the more common immune mediated cases respond well to medications applied to the eye. Cyclosporine eye ointments or drops applied one to three times daily for the rest of the patient’s life will make most pets comfortable and goop free by stopping the rogue immune attack and allowing their tear glands to start doing their job again. For those that don’t respond to the cyclosporine there are some new medications like tacrolimus and pimecrolimus in development that are showing some promise.

Left untreated, dry eyes start developing secondary problems beyond the discomfort of feeling like there is a bucket of sand in the eye all the time. The surface of the eye has difficulty fending off bacterial invaders and can develop ulcers and infections. As a result of the continual irritation the surface of the eye starts to develop a layer of black pigment that can lead to blindness by essentially drawing a curtain across an otherwise normally functional eye. If the immune system is allowed to attack the tear glands for long enough it may succeed in turning them into little wads of scar tissue that can no longer make tears no matter what kind of medication is used.

So next time you spend an afternoon trying to get the gunk out from around your dog’s eyelids, keep in mind that there may be other reasons besides infectious conjunctivitis that could be causing the problem, and getting a diagnosis sooner rather than later may be a good thing for your dog’s comfort and ability to see in the long run.