Cherry eye is a condition caused by a prolapsed or protruding third eyelid gland. This occurs when the normally hidden tear gland located behind the third eyelid herniates upwards into an abnormal position. This occurs mostly in dogs and rarely occurs in cats.
This tear gland is responsible for 1/2 to 1/3 of the tears needed to lubricate the eye. The cause of this condition is thought to be the result of a weakness (or absence) of the ligament that holds the gland in place, which leaves the gland free to dislocate upwardly and out of its normal position.
American Cocker Spaniels, English Bulldogs, Lhasa Apsos, and giant dog breeds are prone to third eyelid gland prolapse, although many other breeds may be affected as well. Cherry eye usually occurs in young dogs less than 18 months of age, but may occur in older patients as well.
Within the folds of the lower eyelid is a thin portion of tissue often called the nictitans or third eyelid, which is found in most domestic animals. A gland called either the gland of the third eyelid, the nictitans gland, or the haw is located on backside of the third eyelid that contacts the ocular surface. This gland produces 30% to 60% of dogs' and cats' tears. The main orbital lacrimal gland, located beneath a portion of the skull bone, produces the rest of the tears. Unfortunately, the amount of tears produced by each of these glands is variable.
The gland of the third eyelid is normally out of sight and held in position behind the third eyelid by a small ligament. A prolapsed gland of the third eyelid, known as "cherry eye," is thought to be associated with a laxity or absence of this ligament. The longer the gland is in an abnormal position the greater risk that the gland will be damaged and not fully functional when it is put back into place.
Whenever your pet is showing signs of a health issue your first step is to contact your primary care veterinarian. If it is indicated that your pet may suffer from cherry eye or another serious condition, a veterinary specialist is available at an ExpertVet-certified or affiliated hospital.
Most pet owners will notice a pink or fleshy appearing lump (a "cherry eye") near the inside corner the affected eye in the corner closest to the animal's nose. Sometimes, this lump will disappear and reappear without treatment before it finally remains in the abnormal position. It may occur in one or both eyes.