This sebaceous gland has been given several names: Harderian gland, Harder’s gland, nictitans gland, deep nictitating membrane, or the medical terms: glandula palpebrae tertiae superficialis or profunda.

The gland was first discovered in the red deer by the Swiss physician Harder (1694). It was subsequently found to be present in amphibians, reptiles, birds and mammals that possess a third eyelid.

The Harderian gland is located within the eye orbit, at the nasal base of the third eyelid. In rabbits, it is composed of 2 lobes:

• A dorsal white lobe;

• A ventral pink lobe.

The white lobe is small, on the contrary of the pink lobe. They cannot be differentiated from each other during a histological analysis, in spite of their different color. Intact male rabbits have a particular large Harderian gland, which increases further in size during the breeding season.

MediRabbit

Normal aspect, with third eyelid protruding over the eye.

MediRabbit

A healthy rabbit eye, with the third eyelid protruding a little.

A swelling of the third eyelid occurs when the ventral pink lobe of the Harderian gland prolapses. The etiology of the prolapse is unknown. A weakness of the connective tissue around the gland is suspected. The gland starts to move, and becomes irritated. Irritation leads to swelling and sometimes discharge. The third eyelid can become bloody and ulcerated, and develops a follicular conjunctivitis.

Diagnosis

The clinical signs should be sufficient for a proper diagnosis. The condition of prolapsed Harderian gland must be differentiated from a retrobulbar fat prolapse or retrobulbar malignant B-cell lymphoma. Malignant B-cell lymphoma was of the Harder’s gland was discovered in a 22 years old rabbit. The retrobulbar mass caused unilateral exophthalmoses. After euthanasia, a necropsy showed the presence of enlarged mesenteric lymph nodes. The cecum and the kidneys were also affected.

The color and appearance of the prolapsed tissue should be indicative: pink and lobular for the prolapsed Harderian gland, white for the retrobulbar fat. The later condition is sometimes observed in obese rabbits.

Akira Yamanouchi

Prolapsed Harderian gland, or “cherry eye”

Treatment

In the past years, the surgical procedure includes the surgical removal of the gland. This is a difficult step in rabbits, as the gland is located around the orbital venous sinus. It has, furthermore, been observed that removal of the Harderian gland led to dry eyes in other animal’s species.

Nowadays, the treatment of a rabbit suffering from a prolapsed Harderian gland is similar as for dogs. The prolapsed gland is pushed back in its pocket, in a slightly deeper position. Janssens and Simoens describe the procedure the following way: “a conjunctival incision is made dorsal to the prolapsed gland and an anchoring suture is placed through the periosteum (dense fibrous connective tissue surrounding bones) of the orbital rim. A horizontal bite is taken through the gland dorsally and the anchoring suture passes ventrally through the gland to exit through the conjunctival incision.”

Kim Chilson

Rabbit suffering from bilateral prolapsed Harderian gland, or “cherry eye”

Kim Chilson

Before surgery

Kim Chilson

Before surgery

The surgical procedure does not necessarily need a full anesthesia, good sedation and local anesthesia is possible when the general health of the rabbit is poor.

Acknowledgement

Thanks are due to Kim Chilson and to Akira Yamanouchi (Veterinary Exotic Information Network, http://vein.ne.jp/), for the permission to use their pictures.

Further information

Flecknell P., editor Gloucester, BSAVA Manual of Rabbit Medicine and Surgery, UK: British Small Animal Veterinary Association2000.

Hillyer E.V. and Quesenberry K.E., Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery, New York: WB Saunders Co.1997.

Janssens G, Simoens P, Muylle S, Lauwers H. Bilateral prolapse of the deep gland of the third eyelid in a rabbit: diagnosis and treatment. Lab Anim Sci. 1999; 49(1):105-9.

Manning P.J., Ringler D.H., Newcomer C.E., The Biology of the Laboratory Rabbit, New York: Academic Press1994.

Donnelly TM. Pink mass on the dorsomedial aspect of a rabbit's eye: cherry eye or prolapse of the deep gland of the nictating membrane. Lab Anim (NY). 2002; 31(2):23-4.

Richardson V., Rabbits: Health, Husbandry and Disease, Blackwell Science Inc 2000.

Volopich S, Gruber A, Hassan J, Hittmair KM, Schwendenwein I, Nell B. Malignant B-cell lymphoma of the Harder's gland in a rabbit. Vet Ophthalmol. 2005 Jul-Aug;8(4):259-63.

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