Dry eye, or "keratoconjunctivitis sicca" is a common eye problem in dogs, especially bulldogs, cocker spaniels, Shih Tzus, and Lhasa Apsos. Identifying and treating dry eye is important, not only to alleviate your dog's discomfort, but also because left untreated dry eye can lead to serious problems, such as ulcers and blindness.
To understand dry eye, you need to understand why the tear film is important. Dr. Amber Labelle, a veterinary ophthalmologist at the University of Illinois Veterinary Teaching Hospital in Urbana, explains that the tear film on your dog's eye serves several functions: it removes waste, such as dust; helps keep the cornea transparent (the cornea is the clear outer portion of the eye); plays a role in immune function; and brings oxygen and nutrients to the cornea. (Remember, unlike most tissues in the body, the cornea contains no blood vessels to bring oxygen and nutrients because blood vessels would keep the cornea from being transparent.)
Learn more about dry eyes from the vet school in Illinois.
NB: In my experience, dogs do not always have eye discharge. Although KCS does need to be ruled out in some cases, the discharge is often a sign of a mild internal imbalance. True dry eye is secondary to immune-mediated destruction of tear gland cells and reduced tear production.--Dr. Jeff
Please note: The information provided here is intended to supplement the recommendations of your veterinarian. Do not disregard veterinary advice or delay treatment based on information on this site. Nothing can replace a complete history and physical examination performed by your veterinarian. -Dr. Jeff