Dog Cherry Eye

Introduction

Cherry eye is the common name for a condition that can affect one or both of a dog's third eyelids, which are technically called nictitating membranes. Nictitating membranes are thin, opaque sheets of tissue that in their normal position are seated underneath the lower eyelids and are not visible. They are closely associated with glandular tissue that contributes to tear production, which is essential to keep the eyes adequately lubricated. The third eyelids also serve to protect the sensitive cornea from physical damage. When the fibrous tissue attachments that anchor the nictitating membranes to the lower eyelids become weakened or loose, the associated tear glands can "pop out" (medically referred to as everting or prolapsing) and become visible as red masses bulging outward from the lower inside corners of the dog's eye. This condition can look alarming – especially because it typically occurs suddenly. Thankfully, cherry eye usually can be treated successfully with a combination of topical medication and surgery.

Causes & Prevention

Causes of "Cherry Eye" in Dogs
The precise causes of cherry eye are not well understood. Anatomically, each eye of domestic dogs contains a nictitating membrane - commonly referred to as a "third eyelid" – which hides beneath the lower eyelid and normally is not visible to owners or to others. Tear glands are located around the cartilage connections of the nictitating membranes, providing a major source of tear film and eye lubrication. However, if the fibrous tissues that hold the third eyelids to the globes of the eyes become weakened, the tear glands can bulge out ("prolapse" or "evert") over or around the third eyelid, appearing as nasty-looking bright red masses. This can happen in one or both eyes of an affected dog. Because cherry eye appears much more frequently in certain breeds, the current consensus is that there is a strong genetic component to the disorder that involves weak fibrous tissue connections associated with the third eyelid. Inflammation (a localized protective response to injury or damage to tissues), as well as tissue hypertrophy (an increase in the size of the third eyelid produced solely by enlargement of existing cells, rather than by new cellular growth) may also play a role in the development of cherry eye.

Prevention of Cherry Eye in Dogs
The precise cause of cherry eye is unknown. However, because it appears more often in certain breeds, it is thought to have a genetic component involving weak connective tissue around the third eyelid. Inflammation and hypertrophy seem to play a role as well.

Special Notes
Cherry eye is a condition that usually occurs quite suddenly. In the typical case, the dog will look normal one minute, and then without warning a large mass of angry red tissue will protrude from the lower inside corner of one or both eyes. Some dogs are born with visible third eyelids along the lower portion of their eyes. These are commonly referred to as "haws". The existence of haws is not the same thing as cherry eye and is almost always only of cosmetic rather than medical concern. Dogs with partially visible nictitating membranes (haws) tend to appear tired, haggard or sad, which is considered unattractive and undesirable – especially in the show ring.

While cherry eye is neither life-threatening nor a true medical emergency, it can cause affected dogs to suffer irritation, inflammation, eye redness (conjunctivitis) and other discomfort. As a result, dogs with cherry eye should visit the veterinarian and be treated promptly to relieve discomfort and prevent permanent ocular damage.

Symptoms & Signs

How Cherry Eye Affects Dogs
Cherry eye can occur in just one of a dog's eyes (unilaterally) or in both eyes (bilaterally). Dogs that develop cherry eye usually have symptoms associated with ocular irritation, dryness, redness (conjunctivitis), swelling, inflammation and/or other causes of pain. Affected dogs tend to scratch or paw at their eyes as a result of the discomfort, and sometimes they are seen rubbing their faces along the grass or indoor carpeting in an apparent attempt to relieve the irritation caused by the condition. The vision of dogs with cherry eye can be adversely affected as well, especially if the surface of the affected eyes becomes scratched, infected or abraded.

Symptoms of Cherry Eye
Owners of dogs that develop cherry eye usually discover it very quickly indeed. The tear glands of the nictitating membranes normally do not slip out of place gradually. To the contrary, they tend to become everted or prolapsed at an alarmingly rapid rate, which causes the associated tear glands to "pop out." Most owners are understandably surprised to see a doughy mass protruding from the lower inside corner of an eye that only moments before appeared entirely normal. The most obvious sign of cherry eye is a well-defined solitary mass of red tissue bulging from the inner corner of one or both of a dog's eyes. Often, this protrusion is the only observable sign that owners see.

If cherry eye is not treated and corrected within a reasonable period of time, the dog can develop additional and sometimes rather serious ocular complications. The gland of the third eyelid contributes a significant part of the fluid that makes up tear film. The primary function of the membrane itself is physical protection of the eye (particularly the cornea). When the nictitating membrane and tear gland are not in the proper place, the eye can become red, dry, irritated and inflamed. There may be abnormal discharge from affected eyes as well. Some dogs act annoyed by the misplaced gland and will rub or scratch at it, which may further damage the eyelid or even cause injury to the cornea. Owners of dogs with cherry eye may notice one or more of the following:

Eye redness (conjunctivitis)
Swelling around the eyes
Excessive tear production – signs of eye drainage
Abnormally dry eyes – insufficient tear production
Rubbing/pawing at the eyes
Squinting
Vision impairment
Other signs of eye irritation.

Dogs At Increased Risk
Cherry eye is most commonly seen in young dogs - typically those less than 2 years of age. Some breeds are predisposed to developing this condition, including Cocker Spaniels, Bulldogs, Beagles, Bloodhounds, Lhasa Apsos, Shih-Tzus and other brachycephalic breeds. Brachycephalic dogs are those with very short flat faces and wide heads.

If you notice that your dog has what looks like a "cherry eye," make an appointment with your veterinarian as soon as possible. This is not a life-threatening condition, but it should be treated promptly to prevent permanent ocular damage.

Diagnosis & Tests

How Cherry Eye is Diagnosed
Cherry eye is a fairly common condition in certain breeds of dogs and is not particularly difficult to diagnose. In fact, diagnosis is almost always made based simply upon a veterinarian's physical examination of the animal; the presence of a glandular tissue mass protruding from the inner corner of a dog's eye is diagnostic of cherry eye. No special tests are needed to confirm that the tear gland associated with a dog's nictitating membrane (third eyelid) has prolapsed or everted. Once it happens, the condition is obvious, clearly visible and rather impossible to ignore.

Owners who notice a red lump of tissue bulging from the inner corner of their dog's eye should take the dog to the veterinarian as soon as possible. Cherry eye is not a true medical emergency, but it is wise to seek medical attention as soon as is realistic in order to prevent permanent damage to the affected eye.

Special Notes
Surgical treatment for cherry eye usually is highly successful. Owners of affected dogs should be sure to discuss available treatment options with their dog's veterinarian in order to arrive at the best possible treatment protocol.

Treatment Options

Treatment Options
Prolapse of the gland of the nictitating membrane or third eyelid - commonly called "cherry eye" - should be treated as quickly as possible. The condition itself is not usually dangerous to dogs. However, effective treatment is necessary to reduce the risk of more serious secondary eye problems, including trauma to the cornea. The longer that the glandular tissue is out of place and exposed to the elements, the more inflamed, irritated, damaged and possibly infected it may become.

Cherry eye in dogs can be treated with topical antibiotic and anti-inflammatory medications and through surgery. Topical therapy can help to reduce the inflammation and irritation commonly associated with this condition. Unfortunately, this course of treatment is rarely successful in preventing recurrence of cherry eye in the long run. In most cases, surgical correction is the only viable permanent treatment option.

At one time, surgical removal of the prolapsed portion of the tear gland associated with the affected third eyelid was the treatment of choice. However, removing the tear gland greatly reduces normal tear production, contributing to severe dry eye and greatly increasing the animal's risk of developing a disorder known as keratoconjunctivitis sicca (KCS) as it ages. If the gland of the third eyelid is surgically removed, the dog will probably need daily supplementary treatment with moisturizing eye drops for the rest of its life.

Prognosis
As veterinary science has learned more and more about the importance of the gland of the nictitating membrane in tear production, surgical repositioning rather than removal of that tear gland has become the treatment of choice for dogs with cherry eye. At least 8 different surgical repositioning techniques have been reported, and more are being considered. The dog's veterinarian will determine which technique to use in a given case. Some pertinent considerations may include the dog's facial structure, the ease of the procedure, its effect on future tear production, the chances of recurring third eyelid gland prolapse and the likely cosmetic outcome of the operation. While selection of the surgical technique is a matter of personal preference, all of the repositioning techniques, when performed properly, should result in a cosmetically acceptable outcome for owners, with a very low chance of recurrence of the condition.

If a dog has only one of its eyes affected by cherry eye, surgical correction of the affected eye will not reduce the risk of prolapse of the tear gland of the third eyelid in the other eye. It is not unusual for a dog to have to go through two separate surgical procedures in order to correct one eye at a time.