Dry eye in cats, also known as keratoconjunctivitis or KCS, is not an uncommon condition in cats and usually occurs as a result of chronic feline herpesvirus illnesses. Dry Eye occurs when the proper amount of tears are not produced by the glands above the eye in the cat's third eyelid. As a result, the cornea of the eye becomes dry, inflamed, and irritated.
KCS is usually defined by the tear glands’ inability to produce water in the tears. Due to the fact that tears are a combination of mostly water with an addition of oil and mucus, if left untreated KCS will result in eyes which have a thick oily mucus layer over the eyes. In most cases, both eyes are affected.
With time, the cornea can become scratched and scarred, and blindness will eventually occur. Dry eye is also a notoriously painful condition, and cats with this illness may also suffer from depression and irritability as a result of their pain.