The pre-corneal tear film (PCTF) comprises an outer lipid, central aqueous and inner mucoid component. Lipid & mucoid components are secreted by the eyelid and conjunctival glands respectively. The aqueous portion of the PCTF is secreted by the lacrimal glands of the orbit and third eyelid. Keratoconjunctivitis Sicca (KCS) may represent a qualitative deficiency resulting from insufficient lipid and/or mucous secretion and/or quantitative deficiency arising secondary to insufficient lacrimal gland secretion. Glandular dysfunction may arise secondary immune-mediated, traumatic, inflammatory, toxic or neurological etiologies.
Pharmacological agents with the potential to cause or exacerbate KCS include etodolac and sulpha-containing anti-microbial compounds. Symptoms of KCS typically include conjunctivitis, vascular/pigmentary keratitis, secondary meibomian gland inflammation/infection and the accumulation of green/yellow-colored mucous in and around the fornices. Commonly affected breeds include the English Bulldog, West Highland White terrier & King Charles Cavalier spaniel.