Dogs possess a third eyelid, known as the nictitating membrane. This eyelid sits diagonally in the inner corner of the eye. The eye is lubricated by tear film, which consists of water, oil, and mucus. Each eye has two glands, one just above the eye and one located in the third eyelid. The gland in the third eyelid is believed to produce between 30 and 60 percent of the total tear film water; so it is important to maintain this gland's function. This article describes a condition that affects the function of the third eyelid gland, which can ultimately cause a reduction in tear film.
What Is Cherry Eye?
In the normal dog eye, you may occasionally get a glimpse of the third eyelid. It may be visible when your pet sleeps or wakes from a nap. Some owners may notice it after their pet has had surgery and are recovering from the anesthesia. When the third eyelid gland thickens and slips out of its proper place, owners will notice a red swollen mass next to the lower eyelid. This leads to the term "cherry eye."
Cherry eye is seen in young dogs, six months to two years of age. The most common breeds affected are cocker spaniels, bulldogs, beagles, bloodhounds, Lhasa apsos, mastiffs, Shih Tzus, and other brachycephalic breeds. Cats are rarely affected, but it has been reported in Burmese and Persian breeds. Unfortunately, cherry eye is not preventable. Knowing what signs to look for can aid in quick diagnosis and treatment.
A red swelling protruding from the edge of the third eyelid is usually the first sign of a cherry eye. This may occur in one or both eyes. Some dogs may not have any other symptoms. Others may have increased tear production, inflamed conjunctiva (a clear mucous membrane that lines the inner surface of the eyelid and the exposed surface of the eyeball), and ocular discharge. If there is a reduction in tear formation, they may experience dry eyes which can cause discomfort.
If you notice your dog pawing at its eyes, or rubbing its face on the floor or carpet, this is a sign there is a problem and you should seek veterinary attention.
What Causes Cherry Eye?
It is not fully understood what causes cherry eye. We do know the lacrimal (tear) gland of the third eyelid is held in place by tissue fibers. Some dogs have weaker fibers so the gland protrudes. In smaller breeds, especially Boston terriers, cocker spaniels, bulldogs, and beagles; the gland of the third eyelid is not strongly held in place because of genetic reasons. When the gland prolapses, it does not circulate blood properly. This results in swelling and the gland may not produce tears normally.
What Treatments are Available?
When a cherry eye is first diagnosed, your veterinarian may recommend a course of anti-inflammatory eye drops, to help reduce the swelling. Antibiotic eye medication may also be prescribed, if there is an associated discharge. If the cherry eye persists and causes discomfort, surgery will be the next step. The best treatment involves replacing the gland back in its proper location. However, when this is unsuccessful, the gland itself may need to be removed.
The Tucking Method
The traditional tucking method (also called tacking) is probably most commonly performed. This technique requires permanently placing a single stitch, drawing the gland back where it belongs. Complications are uncommon but can occur.
- The tuck may not be anchored well enough to hold permanently. This is the most common complication. A second or even a third tuck may be needed. If this fails, another procedure may need to be used.
- The surface of the eye can become scratched if the stitch unties, causing pain for your dog. If this happens, the stitch can be removed, but the cherry eye may return.
- Sometimes the cherry eye is accompanied by other eyelid problems that make the repair more difficult, or less likely to succeed. In these cases, a referral to a veterinary ophthalmologist may be necessary.
The Imbrication Method
Imbrication, or pocketing, is a newer technique. A wedge of tissue is removed from directly over the actual gland. This method poses more of a challenge, because it is often difficult to determine how much tissue to remove. Tiny stitches are used to close the gap. Tightening of the incision margins pushes the gland back in place. The stitches eventually dissolve. Complications can occur including:
- Inflammation or swelling as the stitches dissolve.
- Inadequate tightening of the tissue gap may lead to recurrence of the cherry eye.
- Failure of the stitches to hold and associated discomfort. Depending on the type of suture used, loose stitches can injure the eye.
Sometimes, both tucking and imbrication are used to repair the cherry eye. Your veterinarian will determine which method is the best one to use.
Removal of the Third Eyelid Gland
Removal of the gland of the third eyelid used to be the most popular remedy for cherry eye. Now that we know the full significance of this gland, to produce tear film, this is not the preferred treatment. If the third eyelid gland is removed, and the upper eyelid gland fails to produce adequate tears, a thick yellow discharge results. If this happens the eye develops a blinding pigment covering for protection. This condition is called keratoconjunctivitis sicca, or simply, dry eye. Dry eye usually requires lifelong medication. If left untreated, blindness can occur.
What Can I Expect After Surgery?
Postoperative swelling is very common after cherry eye surgery. This should resolve in about a week. If the eye becomes suddenly painful or unusual in appearance, recheck it as soon as possible. It is not uncommon for the cherry eye to return. To avoid prolonged recovery and complications, make sure you follow all of your veterinarian's post-surgery instructions.
Cherry Eye in Dogs. VCA Animal Hospitals.
Seeing the Signs: What to know about Cherry Eye in Dogs. Texas A&M University Veterinary Medicine and Biomedical Sciences.
Dry Eye (Keratoconjunctivitis sicca). American College of Veterinary Ophthamologists.