The medical term for cherry eye is nictitans gland prolapse, or prolapse of the gland of the third eyelid.
Unlike people, dogs have a 'third eyelid' that contains a tear gland and is located in the corner of each eye. Under normal circumstances this gland is not visible and aids in the production of tears. For some reason, which is not completely understood, the gland of the third eyelid prolapses or comes out of its normal position and swells creating the condition known as cherry eye.
What dogs are likely to get cherry eye?
Any dog can develop cherry eye but there are several breeds that appear to have a higher incidence of developing it in both eyes. They are the Beagle, Bloodhound, Boston Terrier, Bulldog, Bull Terrier, Lhasa Apso, St. Bernard, and Sharpei. Dogs can acquire this condition at any age and it affects males and females equally.
What causes it?
The exact cause is not known, but it is strongly suspected that it is due to a weakness of the connective tissue that attaches the gland to the surrounding structures of the eye. The weakness of the connective tissue allows the gland to prolapse. Once the gland prolapses and is exposed to the dry air and irritants, it can become infected and or begin to swell. There is sometimes a mucous discharge and if the animals rubs or scratches at it they can traumatize the gland further or possibly create an ulcer on the surface of the eye.
What is the treatment?
The treatment is very straightforward and consists of surgically repositioning the gland. Topical or injectable treatments of antibiotics and steroids are rarely effective in reducing the gland and allowing for correction without surgery. Because the exposed gland is at greater risk for further trauma or infection, prompt surgical replacement is the best choice.
At one time it was popular to surgically remove the gland as a way to correct this condition. While this procedure is often effective, it can create many problems later in the animals life. The gland of the third eyelid is very important for the production of tears. Without the tears produced by the third eyelid many dogs could suffer from a serious condition known as dry eye in which they eye does not produce enough tears. When the third eyelid gland is removed we are greatly increasing the chances for the development of this condition. The much better and preferred surgical option is to surgically tack the gland back into place with a suture that attaches the gland to the deeper structures of the eye socket. Most of these surgeries are performed quickly and have very few complications and allow the gland to return to normal function. After the surgery some animals may need to be placed on antibiotic ointment for a few days.