What Are the Causes of Cherry Eye?

"Cherry eye" is the vernacular term used to describe a defective glandular condition common in dogs and some cats. Canines and felines, like many birds, have a translucent third eyelid. This clear mucus membrane, or nictitating membrane, can be drawn over the eye for protection or hydration without compromising visibility. Cherry eye is most common in adolescent dogs, occurring when the normally moist third eyelid prolapses (slides out of place) and gathers in the corner of the eye, becoming exposed to the elements. As the membrane dries out, it becomes irritated, inflamed and bright red. The exact cause of this disorder is debatable, but the consequences--dry eye, stilted tear production, restricted blood flow to the gland, irreversible damage to the organ--are not.

  1. Hereditary Weakness of Connective Tissue

    • Although cherry eye can occur in any breed of dog or cat, it is most common in dogs that are believed to be genetically predisposed to weakness of the connective tissue that holds the third eyelid in place. These breeds include bulldogs, cocker spaniels, Chihuahuas, Shar-Peis, beagles, Neapolitan mastiffs, Basset hounds, Pekingese and Boston terriers.

    Dermatitis

    • Dermatitis is an inflammation of the skin (more commonly referred to as a rash), caused by allergens in the air. Cherry eye is thought, in some cases, to be a form of dermatitis. The nictitating membrane's allergic reaction to irritants such as dust mites, pollen or chemicals leads to swelling and dryness of the third eyelid.

    Glandular Infection: Fungal, Bacterial and Parasitic

    • As the nictitating membrane slips into the corner of the eye, it becomes exposed to the animal's immediate environment--and everything in it. Fungus, bacteria and parasites picked up from the animal's surroundings, feces, paws, toys, neighboring animals--even the air--can be transferred to the exposed membrane, infecting the tear gland and third lid. Without treatment, these types of dangerous infections can exacerbate the symptoms of cherry eye, and potentially jeopardize the animal's sight.