I had a dog with keratoconjuctivitis sicca (KCS) when I was growing up. Unfortunately, the available treatments at the time weren’t that great, so Tangles eventually became blind and surely suffered some discomfort associated with his perpetually "goopy" eyes. Now, however, KCS can usually be managed well enough that dogs don’t have to go through what Tangles did.
Dogs with KCS manufacture fewer tears than normal, and tears are essential to maintaining the health of the eye. Not only do they lubricate the eye’s surface and wash away foreign material, tears also nourish the surface of the eye. Without adequate tear production, a dog’s eyes become inflamed (i.e., red and painful) and produce more mucus than normal. In advanced cases, corneal ulcers, abnormal corneal pigmentation, and loss of vision may develop.
Veterinarians can differentiate KCS from other diseases that cause similar symptoms with a quick and inexpensive procedure called a Schirmer Tear Test (STT). A small strip of filter paper that is usually infused with a dye and marked off in millimeters is folded and inserted between the lower eyelid and the cornea. Tears are wicked up the paper — how high they go is the standard of measurement for the STT. In general, anything less than 15 mm in one minute is considered abnormally low, but the results need to be analyzed in conjunction with the rest of the dog’s ophthalmic exam. For example, because tear production naturally declines somewhat with age, an older dog with an STT of 14 but no signs of KCS probably does not require treatment but should be monitored closely.
Most cases of KCS develop as a result of an abnormal autoimmune response that targets the tear producing glands around the eye. Certain breeds, like the English bulldog, cocker spaniel, west highland white terrier, lhasa apso, and pug are predisposed to this type of KCS. In a few cases, an underlying condition may result in secondary KCS. Diabetes, hypothyroidism, infections, abnormal ocular anatomy, surgery to remove a cherry eye (i.e., a prolapsed third eyelid gland), or the use of certain types of medications (e.g., sulfa antibiotics) may predispose some individuals to dry eye.
Most dogs respond very well to medical treatment for KCS, particularly if it is started early in the course of the disease. Cyclosporine and tacrolimus alone or in combination are generally very effective at reducing inflammation and stimulating tear production when they are applied to the surface of the eye. Artificial tears, topical antibiotics, and other medications may also be prescribed.
Surgery to redirect a duct carrying saliva from the mouth towards the surface of the eye is also an option but should be reserved for those cases when medical treatment is unsuccessful. Saliva isn’t tears, after all, and "crying" instead of drooling in response to a meal has to be an odd sensation.
Tangles lived to a ripe old age, but his quality of life in later years was compromised by KCS. If he had been born a decade or two later, he could have greatly benefited from the relatively recent advances in how we treat this disease.