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Everyday answers for common conditions of the eyelid/conjunctiva (Proceedings)

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Aug 01, 2010

Distichia and Ectopic Cilia

Distichiae are aberrant hairs that arise from the meibomian glands and exit through the meibomian gland opening in the eyelid margin. Distichiasis occurs commonly in many breeds of dogs. In some breeds the hairs cause virtually no clinical signs (e.g., Cocker Spaniels), whereas in other breeds they can result in epiphora, corneal fibrosis and vascularization, and occasionally corneal ulceration. The presence or absence of clinical signs depends on the number of hairs, their length, their rigidity, and the eyelid conformation of the dog. Ectopic cilia hairs arise from the same location in the meibomian glands but they exit through the palpebral conjunctiva and are much more likely to cause corneal irritation and ulceration. A non-healing superficial ulcer in the dorsal cornea of a young dog is the classic clinical presentation for an ectopic cilia hair. Magnification is required to see many ectopic cilia. They can be highlighted by a surrounding area of pigmented conjunctiva. The application of fluorescein stain can help to highlight the cilia in some cases.

Distichiae can be manually epilated, but will normally grow back in three to four weeks and the regrowth can be more rigid and more irritating than the original hairs. The hairs can be electroepilated with a surgical cautery unit, but this requires high magnification and is tedious. Cryoepilation is the quickest procedure for treatment of large numbers of distichia. Either nitrous oxide or liquid nitrogen can be used. A chalazion forcep is applied to stabilize the lid and the lid is everted to expose the palpebral conjunctiva. The cryoprobe is placed at the base of the meibomian glands and applied until the iceball extends to the meibomian gland opening at the lid margin. The iceball is allowed to completely thaw, and freeze/thaw cycle is repeated if using nitrous oxide. If using a liquid nitrogen cryogun, only a single freeze/thaw cycle is necessary. Several sites can be frozen before moving the chalazion forcep to another location. Ectopic cilia are first surgically excised and then the area is treated with cryotherapy. Eyelid swelling and depigmentation of the eyelid margins are anticipated sequelae following cryoepilation. Clients should be advised of this, particularly if the patient is a show-dog. Swelling is transient and pigmentation often returns in a few months. Topical antibiotic/steroid ointment is recommended q 12 hours post-operatively unless an ulcer is present. Oral non-steroidal anti-inflammatories or corticosteroids can be used to control postoperative swelling and inflammation. The use of the CO2 laser to ablate ectopic cilia and distichia is not recommended. Ectopic cilia treated with the CO2 laser ablation have a high rate of recurrence. Treatment of multiple distichia with the laser can cause significant lid margin scarring and lid distortion.

Prolapsed Gland of the Third Eyelid and Its Replacement

Although it is much easier to excise a prolapsed gland of the third eyelid, the current standard of care is surgical replacement of the gland. The gland of the third eyelid is estimated to produce 30% of aqueous tear film and excision of the gland may predispose some animals to the development of dry eye. The correlation between gland excision and the development of dry eye is often not made because prolapse occurs in young animals, whereas dry eye usually develops in middle-aged or older dogs. In most dogs the pocket technique is sufficient to treat the prolapsed condition of the gland. In some breeds however, orbital or scleral tacking or even a dual procedure is required for successful treatment of the prolapsed gland. In the pocket technique, approximately 1 cm curvilinear incisions are made in the posterior third eyelid conjunctiva, above and below the gland. The conjunctival tissue is undermined to free the edges. Without excising any tissue, the incisions are re-apposed using 6-0 Vicryl in a continuous pattern in one direction and returning to the starting point with an inverting pattern. The suture line is begun and tied off on the palpebral aspect of the third eyelid to prevent corneal irritation by the suture. To prevent the formation of a lacrimal cyst, the medial and lateral extent of each incision should be left open creating an exit site for tears after surgery. Post-operative treatment is with triple antibiotic ointment with or without steroid q12 hours for 10-14 days.

Entropion

Entropion is a primary conformational defect that is found as a congenital/developmental in young dogs. Entropion can also be found secondary to injury, corneal pain or atrophy of retrobulbar fat. Spastic entropion, secondary to ocular pain can normally be differentiated from primary entropion by applying a topical anesthetic to the globe. Cases of primary entropion may also be complicated by a spastic component and this should be determined prior to making a surgical correction.