Scanning electron microscopy of experimental keratoconjunctivitis sicca in dogs: cornea and bulbar conjunctiva

Keratoconjunctivitis sicca was produced experimentally in 16 beagles by bilateral surgical removal of the lacrimal and nictitans glands; four dogs were not treated, and 12 received tear-replacement therapy on post-operative days 7 through 28. Keratoconjunctivitis sicca was verified by reduction in Schirmer tear test values by post-operative day 6, and there was no response on day 28 to tear-replacement therapy. Corneas of both normal and tear-deficient dogs had polygonal squamous epithelial cells of light and dark electron density by scanning electron microscopy. Light cells had more microvilli and microplicae than dark cells. Conjunctivae were similar to corneas, except for numerous goblet cells on the surface. Corneal dark-cell density and goblet cell density were not different between groups. Goblet cells most often occurred singly in normal dogs, while they were in clusters in tear-deficient dogs. A hypothesis that petrolatum/mineral oil ointment should provide more effective artificial tear replacement than hydroxymethylcellulose drops for tear-deficient dogs could not be confirmed by objective analysis of corneal dark-cell density or conjunctival goblet cell density.