Causes of Cherry Eye
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.
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.