A small gland is on the back side of the third eyelid, the side that lies against the eyeball. The third eye is called the nictitating membrane. It is the eyelid that owls use to slide over their eye. Normally the gland of the third eyelid is not seen. Only when the gland gets infected does it enlarge and protrude from the third eyelid.
A small ligament that holds the gland in place stretches or breaks for unknown reasons. When the gland suddenly breaks free of its attachment, it protrudes over the third eyelid and looks like a small cherry, thus “cherry eye.” The gland produces about 35 percent of the watery tears, and the longer it stays out and exposed, the less functional it becomes. If the gland becomes nonfunctional, then tear production diminishes to the point that a “dry eye” occurs, which causes chronic infection and even blindness.
A smooth round, pink mass is visible in the corner of the eye nearest the nose. The mass looks like a cherry pit, thus “cherry eye.” The condition is not usually painful. A thorough ocular exam is always performed, especially a test to measure tear productions and using stains to make sure that the cornea has not been damaged.
Because this gland is responsible for one third of the eye’s tear production, the preferred treatment is to surgically replace the gland. Surgical removal of the gland may be considered as a last resort if the replacement techniques fail, or if the gland has been prolapsed for so long that it is no longer functional.
Postoperatively, two tests are always necessary. First, tear production tests, called Schirmer tear tests, are necessary monthly. Second, fluorescein stain tests are necessary to monitor any corneal damage secondary to the decreased tear production.
Though surgical techniques guarantee success, many tear glands remain in place following surgery. Success is highest when the surgery is done soon after the prolapse has occurred, and when the gland is still healthy.
“Dry eye,” or the lack of tear production caused by “cherry eye” is very prevalent, so early surgical treatment is strongly recommended. If you see this unique swelling in the nasal corner of your dog’s eye, see your veterinarian immediately.
Dr. Karsten Fostvedt is a veterinarian at St. Francis Pet Clinic in Ketchum.