Canine Conjunctiva and Nictitating Membrane (Nictitans)

Diseases of the canine conjunctiva and nictitating membrane are common in the dog, and for the most part easily visualized and diagnosed. Neoplasms of the conjunctiva and nictitans are less frequent than those affecting the eyelids, but are less predictable and decidedly more malignant. The nictitans, as an appendix of the medial conjunctiva, functions with passive dorsolateral movements across the cornea. Eversion or inversion of the leading margin of the nictitans occurs in the large and giant breeds of dogs. "Cherry eye" or the inflammation and prolapse of the tear gland of the nictitating membrane is a common disease of dogs less than 1 year of age, and affects certain breeds commonly, especially the American Cocker Spaniel, Boston Terrier, Miniature Schnauzer, English Bulldog, and Beagle. Plasma cell infiltration or plasmoma of the nictitans appears as an immune-mediated disease in which the nictitans becomes infiltrated with plasma cells and lymphocytes, with follicle formation and depigmentation.