When my friend saw a big pink round mass bulging out of the eye of her beagle-dachshund-mix puppy, she was alarmed. Was it a sudden-onset tumor? Had a bee stung the dog's eye? Why did her sweet puppy suddenly look like a zombie dog?
A quick trip to the veterinarian calmed her fears and identified the problem as "cherry eye," a condition in which a gland located below the inner corner of the eye protrudes or "prolapses," flipping up and coming out of the eye. (See http://www.cvm.uiuc.edu/petcolumns/images/cherry_eye.jpg for a photo.)
According to Dr. Erica Tolar, veterinary ophthalmology resident at the University of Illinois Veterinary Teaching Hospital in Urbana, this gland is connected to the dog's third eyelid. Unlike humans, most other animals have a third eyelid, also know as a "nictitating membrane," which provides extra protection for the eye. In dogs and cats, this eyelid is sometimes visible at the inside corner of the eye.
The gland of the third eyelid helps protect the eye, so it's important not to remove it. It produces about 35 percent of tears and also serves immunological functions, providing natural antimicrobial substances such as antibodies and lysozyme, an enzyme that can inactivate bacteria.
Dr. Tolar attributes many cases of cherry eye to a congenital defect in the ligament that normally holds the gland in place. The condition is most common in dogs under 2 years old, especially breeds such as English bulldogs and Cocker spaniels. Cherry eye is uncommon in cats.
If left untreated, a prolapsed gland of the third eyelid may become irritated and inflamed from constant exposure, but often cherry eye does not cause many complications.
A prolapsed gland may be surgically repositioned into its normal anatomical position through surgery, but one common complication of this surgery is the tendency for the gland to come back out.
If the gland has been surgically repositioned two or three times but still keeps coming out, Dr. Tolar says some veterinarians will opt to leave the gland as it is. "Generally cherry eye is only a cosmetic problem. It looks weird, but it's not always irritating to the animal."
If a prolapsed gland is left out, with time it may become pigmented and decrease in size.
Dr. Tolar does not advocate removing a prolapsed gland. "Even if the gland is sticking out," she says, "it's still functional, it's still producing tears. This gland produces a portion of tear film, so if it is removed, dry eye (a tear deficiency) may result."
Nevertheless, Dr Tolar recommends a veterinary examination of any mass in or around a dog's eye. "With older dogs the problem could be a tumor. A veterinarian can help distinguish between a tumor and cherry eye," she says.
For more information about cherry eye, consult your veterinarian.
Veterinary Extension/Office of Public Engagement University of Illinois College of Veterinary Medicine 217/333-2907