My first patient of the day is a soft, five year old Cavalier King Charles Spaniel named Chelsea. She looks at me suspiciously through half-open eyelids as her family describes the goopy eye discharge that goes away with topical medication but reappears once treatment is stopped. Chelsea are no longer as keen on playing ball as they were before and spend most of their time curled up in their bed – behavior hardly expected from a champion ball catcher.
I take a closer look at her eyes with my slit lamp and see thin blood vessels growing in crystal clear corneas. Instead, they’re hazy gray, and the conjunctiva – the lining that covers the exposed part of the eyeball and lines the inside of your eyelids – is red and swollen. I use special little strips of paper, divided in millimeter increments, to measure Chelsea’s tear production and find that she is less than a third of what she should have. I then apply a topical stain that coats your cornea in a rough and blotchy pattern. The combination of Chelsea’s medical history, her eye exam, and the test results gives me a diagnosis: keratoconjunctivitis sicca.
What is keratoconjunctivitis sicca? Keratoconjunctivitis sicca (KCS), also known as “dry eye,” is a chronic inflammatory disease in dogs that does not produce enough tears to properly lubricate the eyes. KCS is just a canine eye disease that can affect the precorneal tear film (PTF), which keeps the cornea and surrounding eye tissue healthy. The function of the PTF is to supply oxygen and nutrients to the eye tissue and to remove debris from the surface of the eye.
Causes of Dry Eye in Dogs
In most cases, KCS is caused by an immune-mediated problem that causes inflammation in the tear glands and decreases the amount or quality of tears they produce. Some drug interactions and systemic health conditions, such as hypothyroidism, can also affect the tear film, as can damage to the nerves that cause these glands to work properly. Additionally, the movement of the eyelids spreads the tear film across the cornea, so a dog’s inability to blink fully can also affect eye health.