Third eyelid gland prolapse

The third eyelid, also known as the nictitating membrane, is a structure that sweeps over the surface of the eye in order to spread tears across the cornea and protect the eye. It is usually only possible to see the edge of the third eyelid which is located in the lower corner of the eye near the nose.

Other names for third eyelid gland prolapse are nictitans gland prolapse, and ‘cherry eye’.

There is a gland located behind and deep to the third eyelid that is not usually visible. This gland has an important function of making tears, and it contributes around one-third of the tear volume of the eye. Adequate tear production is essential to keep the surface of the eye moist and healthy.

Third eyelid gland prolapse occurs when this gland moves from its deep location and protrudes over the free edge of the third eyelid. This prolapsed third eyelid gland appears as a pink swollen mass in the corner of the eye and because of this is commonly referred to as ‘cherry eye’. Although cherry eye is not usually painful, it is often associated with conjunctivitis and the prolapsed gland may become inflamed and lead to lowered tear production (‘dry eye’).

Third eyelid gland prolapse can affect one or both eyes. It is not known what triggers the prolapse, but it is more common in certain dog breeds (American Cocker spaniel, English and French Bulldogs, Shi Tzu, Lhasa Apso, Pekingese, Shar Pei, Beagle, Great Dane and Mastiff breeds).

The only effective treatment is to surgically return the gland to its normal position. There are a number of ways this can be done. The simplest and most effective technique involves burying the gland in a pocket of conjunctiva behind the third eyelid and then suturing the pocket closed. This method has a high success rate and allows the third eyelid to continue to move normally. Following surgery, a short course of antibiotic eye drops and pain relief tablets are given.

There are other surgical techniques available and these may be used in selected patients or in some rare cases when the ‘pocket’ technique has been unsuccessful.

Surgical excision of the third eyelid gland is not recommended, because in more than 50% of cases it will lead to the development of ‘dry eye’ (keratoconjunctivitis sicca). Dry eye is painful and can be blinding.