PROLAPSED NICTITANS GLAND IN A DOG

History

A ten month old female Dogue de Bordeaux presented with a sudden onset, fleshy pink mass at the medial canthus of the right eye.

Examination

A full clinical examination was undertaken along with an ophthalmic examination as per Appendix 1. All relevant findings are recorded below.

OS: - Ocular examination unremarkable

OD: - Moderate hyperaemia of lower lid and third eyelid conjunctiva

- Lymphoid follicular hyperplasia on third eyelid

- Conjunctival covered mass 10mm x 5mm present between free edge of third eyelid and cornea (fig. 31)

OU: - Overlong upper and lower lids with tendency towards "diamond eye" conformation

STT L = 18mm/minute, R = 20mm/minute

Differential Diagnoses

- Prolapsed nictitans gland

- Cyst associated with the nictitans gland

- Neoplasia of one of the structures of the nictitans

- Scrolled cartilage of the third eyelid

Treatment

Fucidic acid 1% (Fucithalmic, Leo) BID OD

Carprofen (Rimadyl, Pfizer) 2mg/kg BID

PO General anaesthesia was performed as per Protocol 2, Appendix 2. The conjunctiva and ocular surface was prepared for surgery as per Appendix 3. The periocular hair was not clipped, however this area was lavaged with 10% iodine solution.

The third eyelid was prolapsed and everted, then held in place with forceps applied to the free edge. This exposed the bulbar surface of the third eyelid and the enlarged bulbous nictitans gland mobile on the mid part of the lid (fig. 32). An incision was made globe side of the prolapsed gland along the length of the gland. The conjunctiva was freed from the third eyelid by blunt dissection towards the limbus. A similar incision was made on the free edge side of the gland and the conjunctiva elevated by blunt dissection towards the free edge. These incisions do not meet however do curve gently towards each other at each end.

The third eyelid was replaced in an uneverted position. A knot was tied in 0.7metric polyglactin (Vicryl, Ethicon) on the palpebral surface of the third eyelid. The suture was passed through the third eyelid, which was then everted again, to exit close to one end of the surgical incisions. The opposing edges of the two surgical incisions were closed with a continuous suture taking care not to expose portions of the suture material to potentially rub on the cornea. The conjunctiva was pulled over the exposed gland creating a "pocket" in which it was held (fig. 33). At the end of the surgical incisions the suture was again passed onto the external surface of the lid to be knotted. Gaps were left at the ends of the two incisions to allow passage of the tear secretions, which are secreted onto the surface of the nictitans gland through small pores. At the end of surgery the third eyelid was replaced into its normal position (fig. 34).

Discussion

Prolapse of the nictitans gland or "cherry eye" is seen particularly in some breeds, of which the Bulldog, Beagle, American Cocker Spaniel and Lhasa Apso are reportedly the most common (1). All of the breeds with a tendency towards slack eye conformation and "diamond eye" are over represented. It has also been reported in the cat but much less commonly (2). The third eyelid is found medioventrally in the fornix and is a fold of conjunctiva supported upon a T shaped cartilage with the horizontal part of the T giving shape to the free edge. The nictitans gland is found on the bulbar side of the third eyelid at the base of the T shaped cartilage. It is anchored down to the base of the third eyelid by an ill defined ligament down to the orbital rim. The gland is believed to prolapse due to a defect in this ligament. The gland produces both serous and mucus components of the tear film.

The exposed gland can become inflamed and swollen as well as looking cosmetically unattractive. Previously it was common practice to excise the gland however this gland contributes significantly (30-50%) to the aqueous component of the tear film. Its removal was found to significantly increase the risk of keratoconjunctivitis sicca (KCS), especially as it tends to occur in breeds already predisposed to KCS (3, 4). Leaving the gland prolapsed interferes long term with its tear production so is also a poor option. It is now accepted that best practice is to replace the gland to maintain tear production. Gland removal not only removes a source of tears but also decreases the amount of glandular tissue remaining to respond to any KCS treatment. Even in dogs free from ocular disease the removal of the gland causes qualitative changes in the tear film (decreased basal tear production and shortened tear break up time) (4, 5).

Multiple surgical techniques have been described to replace the gland but the two predominant ones are the pocket technique performed above, described by Morgan et al (1) and the periosteal suture anchoring technique described by Kaswan and Martin (2). The anchoring technique is technically more difficult to perform and had a higher failure rate in one study (1). It also ties the third eyelid down towards the orbital rim making it less mobile and therefore unable to perform its task of spreading the tear film. The pocket technique is simple to perform and replaces the gland back in its anatomical position. No suture material is permanently left to act as a possible nidus of infection and the function of the third eyelid is not compromised. The method can easily be repeated if it fails however in such cases it is prudent to try another technique or combination of techniques.

Both techniques help preserve the structure and function of the gland and thus the tear film, hopefully avoiding the potential sequel of KCS.

References

1. Morgan RV, Duddy JM, McClurg K (1993) Prolapse of the gland of the third eyelid in dogs : a retrospective study of 89 cases (1980 - 1990) Journal of the American Animal Hospital Association 29, 56 - 60.

2. Barnett KM, Crispin SM (1998) In: Feline Ophthalmology, An Atlas and Text, Saunders, p 57.

3. Kaswan RL, Martin CL (1985) Surgical correction of third eyelid prolapse in dogs. Journal of the American Veterinary Medical Association, 186 (1), p 83.

4. Dugan SJ, Severin GA, Hungerford LL, Whiteley HE, Roberts SM (1992) Clinical and histologic evaluation of the prolapsed third eyelid gland in dogs. Journal of the American Veterinary Medical Association 201 (12) 1861 - 1867.

5. Saito A, Izumisawa Y, Yamashita K, Kotani T (2001) The effect of third eyelid gland removal on the ocular surface of dogs. Veterinary Ophthalmology 4, 13 - 18.

Figure 31: Prolapsed gland before surgery.

Figure 32: Third eyelid everted.

Figure 33: Gland replaced in conjunctival pocket.

Figure 34: Third eyelid replaced in normal position.