An editor at Catster recently asked about tear production in cats. Executive editor Vicky Walker‘s friend, Bisi, adopted a cat who does not consistently produce tears in one eye. Chesta the tabby receives eye drops several times each day, but the eye remains painful and itchy. Why does this happen, and what can be done about it?
Tears, as I’m sure most people can surmise, are important. Here’s why:
Tears, therefore, are the figurative lifeblood of the cornea. And as you can imagine, a lot can go wrong when a cat can’t produce tears. The affected eye will feel dry, scratchy, and itchy. It will become irritated and red. The cat will experience pain that will cause squinting. The eye will be prone to infections and ulcers (erosions) on the cornea.
The syndrome in which cats produce insufficient tears has a formal medical name: keratoconjunctivitis sicca, or KCS. It is known colloquially by a simpler name: dry eye.
In most cases, the answer is unknown. There are no gender, breed, or age predilections that have been reported. However, there are known risk factors. Infection with the feline herpes virus is the leading risk factor. The mechanism by which feline herpes causes KCS is unknown, and the virus clearly does not cause KCS in every infected cat. In fact, almost every cat on earth is infected with herpes, and KCS mercifully is uncommon. However, in some individuals herpes triggers KCS. Certain other types of eye infections, especially if recurrent, and some hereditary issues in which the eyelids don’t develop properly also are known risk factors for KCS.
The other known risk factors for dry eye in cats are human (by which I mean veterinarian) generated. Most important, surgical removal or derangement of portions of the tear-producing apparatus are likely to cause KCS. This is most relevant in Burmese cats, who are prone to a condition in which one of the tear producing glands in the third eyelid dislodges from its proper position. The condition, colloquially called cherry eye, is common in the breed. It results in an unsightly fleshy protuberance in the center portion of the eye. If the condition is not treated, or is treated improperly, KCS is likely to develop.
Since my editor’s cat is not Burmese — she’s a tabby shorthair — and hasn’t undergone any eye surgeries, her KCS likely occurred naturally.
First, the diagnosis must be confirmed. This involves a test in which strips of paper are placed in the eye to measure tear production. I personally have endured this test, and it’s not very pleasant, because the test only works when the paper irritates the eye in order to stimulate tears.
In cats, measuring tear production is further complicated by the fact that stress causes reduced tears in the species. Going to the vet is stressful for many cats, so false positive tests for KCS are not uncommon. However, a specialist in veterinary ophthalmology should be able to interpret the results in an accurate fashion.
For cats who have naturally (non-surgically induced) cases of KCS, the prognosis is fair to good with appropriate treatment. A specific type of eye drop containing an ingredient called cyclosporine can bring tear production back to normal in most cats. Many cats also are treated for herpes infection. Less often, an oral medication called pilocarpine may be used; this medication may cause gastrointestinal upset, so it is not usually the first choice.
It may take several weeks or even months for tear production to rebound. During that time, artificial tears (lubricating ointments that help to protect the eye) may be used as a stopgap measure. Ophthalmic antibiotics may be prescribed for secondary infections and ulcers. Unfortunately, surgically induced KCS often is non-responsive to cyclosporine and pilocarpine, and therefore the less effective artificial tears may be used as a long-term option.
Longstanding dry eye leads to chronic pain, infections, and potentially vision compromise. It is therefore important to manage the syndrome appropriately. I recommend that my editor’s friend consult with a specialist in veterinary ophthalmology. Such specialists are common in urban areas, and can be found at veterinary school teaching hospitals in many rural areas. An eye specialist will offer the best hope for restoring tear production and preventing complications.
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