Dogs have an opaque third eyelid called the “nictitating membrane”. It is located at the inner corner of each eye and, in normal conditions, this third eyelid is inconspicuous.
There is a major tear gland wrapped around the cartilage of the third eyelid which is the production source of about 35% of tears for the eye.
Sometimes, for some reason, the tear gland of the third eyelid prolapses or swells and bulges out of its normal “hidden” position. This exposes the tear gland which is a red mass that looks like a cherry. That’s why this condition is commonly known as “cherry eye”.
Medically, dog cherry eye is known as “nictitans gland prolapse”, or prolapse of the gland of the third eyelid.
Causes of Cherry Eye in Dogs
The exact cause of dog cherry eye is unknown although it is believed to be a congenital defect.
In a dog with cherry eye, the connective tissue that attaches the gland of the third eyelid to the surrounding eye structures is weak.
Due to this weakness, the gland comes out of its normal position and is exposed to the air. It comes into contact with airborne irritants, which can cause infection to the gland. As a result, the gland often becomes irritated, red, and swollen.
Breeds that are predisposed to cherry eye include:
- Cocker Spaniels
- Boston Terriers
- English Bulldogs
- Chinese Shar-Peis
- Saint Bernards
- Miniature Poodles
- Shih Tzu’s
Symptoms of Cherry Eye in Dogs
Besides the pinkish red cherry-like mass in the corner of the eye, a dog with cherry eye sometimes has a watery or mucous discharge from the eye.
The conjunctiva (lining of the eyelid) may become red because the protruded gland can irritate the surface of the eye, causing recurrent conjunctivitis.
In addition, if the dog rubs or scratches at the protruded gland, the gland will become traumatized further and an ulcer on the surface of the eye may result.
Treatment of Cherry Eye in Dogs
The treatment of choice is to undergo surgery to reposition the third eyelid and the tear gland.
This can correct the condition and at the same time maintain tear production. Most of these surgeries involve simple procedures and can be performed with very few complications.
However, there is a 5% to 20% chance of the condition recurring, depending on various factors. Some such factors include how big the gland has become at the time of surgery, and how long the prolapse has occurred.
After the surgery, the dog may need to be placed on antibiotic ointment for a few days.
Complete removal of the third eyelid and the tear gland is not advisable because it will seriously interfere with the production of tears. Removing this gland will result in a condition called dry eye (keratoconjunctivitis sicca).
Medical treatment involves using topical antibiotics and anti-inflammatory corticosteroid medications to decrease inflammation of the prolapsed gland and/or the conjunctival membrane.
Note, however, that while topical medication can reduce inflammation and stop infections, it cannot return the third eyelid and tear gland to a normal position.
If your dog has had surgery to treat his cherry eye, be sure to carefully monitor the production of tears in the affected eye to make sure that it is functioning normally. It is still possible for dry eye to develop months to years following prolapse of the gland, even though the condition has been reversed by surgery.