Canine Keratoconjunctivitis Sicca Study Guide

Overview and Clinical Importance

Keratoconjunctivitis sicca (KCS), commonly known as "dry eye," is a chronic inflammatory condition of the cornea and conjunctiva resulting from deficient tear production. KCS is one of the most common ocular conditions in dogs with a reported annual incidence of 0.3% to 1.5% in North America. The term derives from Greek and Latin roots: "kerato" (cornea), "conjunctivitis" (inflammation of conjunctiva), and "sicca" (dry).

Without adequate aqueous tears, the cornea and conjunctiva become dry, inflamed, and susceptible to secondary bacterial infection, ulceration, and progressive scarring. If untreated, KCS can lead to corneal pigmentation, neovascularization, and potentially permanent vision loss. Early diagnosis and lifelong management are critical for maintaining ocular comfort and preserving vision.

Anatomy and Physiology of the Tear Film

The precorneal tear film (PTF) is a thin, complex layer essential for corneal health. It provides lubrication, delivers oxygen and nutrients to the avascular cornea, removes debris and pathogens, and creates a smooth optical surface for light refraction.