The lacrimal or tear gland, located at the top outer edge of the eye, produces the watery portion of tears. Nasolacrimal ducts allow tears to drain from each eye into the nose. Disorders of these structures can lead to either eyes that water excessively or dry eyes. They may be congenital (present at birth) or caused by infection, foreign objects in the eye, or trauma.
Cherry eye is a common disorder in young dogs and certain breeds (for example, American Cocker Spaniel, Lhasa Apso, Beagle, Pekingese, and English Bulldog). In this disorder, the gland of the nictitating membrane thickens, slips out of its proper place, and sticks out over the edge of the membrane. The resulting red, swollen mass next to the lower eyelid leads to the name “cherry eye.” A pus-filled discharge may also be seen. Although the swelling may go down for short periods, the nictitating membrane gland often remains dislocated.
Because this gland is important in the production of tears, your veterinarian will want to preserve it, if possible. The gland is often put back in place and stitched to the connective tissue around the edge of the eye or covered with nearby mucous membrane using an envelope or pocket technique. Partial removal of the gland is usually avoided. Dogs that have cherry eye appear to be more likely to develop dry eye (see below) later in life, especially if the gland is removed.
Inflammation of the tear sac is usually caused by obstruction of the tear sac and the attached nasal tear duct by inflammatory debris, foreign objects, or masses pressing on the duct. It results in watering eyes, conjunctivitis that is resistant to treatment, and occasionally a draining opening in the middle of the lower eyelid. If your veterinarian suspects an obstruction of the duct, he or she may attempt to unblock it by flushing it with sterile water or a saline solution. X-rays of the skull after injection of a dye into the duct may be necessary to determine the site, cause, and outlook of longterm obstructions. The usual therapy consists of keeping the duct unblocked and using eyedrops containing antibiotics. When the tear duct has been irreversibly damaged, surgery may be necessary to create a new drainage pathway to empty tears into the nasal cavity, sinus, or mouth.
The condition known as dry eye results from inadequate tear production. It often causes a persistent, thick eye discharge and reddened eyes. There may also be slow-healing sores and scarring on the cornea. In dogs, it is often associated with an autoimmune inflammation of both the tear and nictitans glands. Less frequent causes of dry eye in dogs are distemper (a viral disease), therapy with sulfonamide antibiotics, heredity, and injury. To treat this condition, your veterinarian may prescribe eye medications to increase tear production (such as cyclosporine), increase moisture (artificial tear solutions), and reduce mucus. If there are no sores on the cornea, an antibiotic-corticosteroid combination may be added. An additional medication may be added if the dry eye is due to a neurologic condition. In long-term dry eye resistant to medical therapy, surgery may be required to correct the condition. In general, the condition requires longterm—often lifelong—use of eye medications.
Also see professional content regarding nasal cavity and tear duct disorders.