What is ... ?:

The third eyelid is a triangular shaped structure in the inner corners of your dog's eyes that you may notice sometimes partly covers the eye. It consists of a t-shaped cartilage to provide support, and a tear gland. The third eyelid is important in protection of the surface of the eye, and in tear production. It is also called the nictitating membrane (or membrana nictitans) and haw.

Abnormalities:

A prolapse of the gland or "cherry eye" occurs when the base of the gland (embedded in the cartilage) flips up and is seen above and behind the border of the third eyelid. The prolapsed gland becomes swollen and inflamed. The condition frequently occurs in both eyes and is most common in young dogs of the breeds listed below.
Eversion of the cartilage appears as a scroll-like curling of the cartilage, usually in an outward direction, although inward curling also occurs (inversion of the cartilage). It is most common in young large breed dogs.
Another condition of the third eyelid is atypical pannus. This occurs in German shepherds.

Image:

How is ... inherited?:

It has not been proven that this condition is inherited, but dogs of the breeds listed below are predisposed.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

Both conditions cause chronic irritation of the conjunctiva and cornea, and if untreated, can lead to keratoconjunctivitis sicca.

How is ... diagnosed?:

Both conditions generally occur in younger dogs and are readily diagnosed from the appearance of the eye. In cherry eye, the glandular tissue protruding behind the third eyelid may be markedly swollen and inflamed. It must be distinguished from a tumour of the third eyelid, which is rare.

How is ... treated?:

prolapsed gland: The gland and cartilage are anchored surgically in the proper position. Sometimes the prolapse recurs. The gland itself must not be removed, as inadequate tear production will result causing keratoconjunctivitis sicca.

eversion of cartilage: The abnormal folded cartilage is removed surgically.

Breeding advice:

It is preferable not to breed dogs that have developed these conditions.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Gelatt, K.N. 1991. Veterinary Ophthalmology. Lea and Febiger.

prolapse of nictitating membrane

Third eyelid (nictitating membrane) abnormalities - "cherry eye"