The health of the eyelids is intimately linked with the health of the globe. As small animal practitioners, it is critical that we remember the importance of eyelids in relation to the preservation of vision. Adnexal structures function to protect the globe, produce 2 of the 3 components of the precorneal tear film, spread the tear film over the corneal and conjunctiva! surfaces, prevent tear evaporation, and promote normal tear drainage. Physical or functional abnormalities of the eyelids may result in chronic irritation and ocular pain, corneal pathology, and even decreased vision or loss of the globe.

Conformational and acquired eyelid abnormalities are common in small animal patients, with dogs much more frequently affected than cats. The goal of treatment, whether surgical, medical, or combination of both modalities, is the restoration of normal eyelid structure and function, within the conformational constraints of the individual patient and breed-specific characteristics. Corrective eyelid surgery should be undertaken only with appropriate ocular instrumentation and suture material. The complete ophthalmic examination should always be performed prior to undertaking any definitive surgical repair to carefully rule-out underlying ophthalmic disease that may be contributing to a conformational or acquired eyelid disorder. Look carefully for differences in eyelid position or function that may occur after instillation of topical anesthetic solution (e.g., avoid over-correction of entropion by blocking the “spastic component” of conformational eyelid entropion with topical anesthetic).

A basic understanding of adnexal anatomy is essential for the practitioner performing eyelid surgery. The eyelids consist of a fibrous tarsal plate (which is poorly developed in the dog), which provides some structural rigidity to the eyelid, muscles primarily involved in blinking, thin, mobile, and pliable skin on the outer surface, and palpebral conjunctiva on the inner surface. A number of adnexal specializations, such as cilia (eyelashes)and glands, exist in our small animal patients. Although species variability exit, typically cilia are present on the outer surface of the upper eyelid margin in dogs, horses, cattle, pigs, and sheep. A few cilia also are present on the lower eyelids of horses, cattle, and sheep. Cats have no true cilia but do have a line of modified hairs that function similarly. Cilia have a protective role and may improve the sensitivity of the eyelids to potentially noxious stimuli, thereby increasing the speed by which reflexive blinking protects the globe. The tarsal or meibomian glands are modified sebaceous glands that are present within the tarsal plate and open at the eyelid margin immediately posterior to the cilia. Their orifices are visible grossly, and mebum - a grayish-white secretion rich in phospholipids that has a lower melting temperature than sebum on the skin - is expressed from them; their opening forms an important surgical landmark, referred to as “the gray line” by some ophthalmologists. This small ridge of lipid along the eyelid margins helps minimize overflow of tears (epiphora). Mebum forms the more superficial lipid layer of the precorneal tear film, which adds stability to and reduces evaporation of the aqueous layer of the tear film.

Importantly, any blepharoplastic procedure should only be performed by the veterinarian who has personally evaluated the awake, non-sedated affected animal. This helps to ensure that the practitioner performing eyelid surgery has a complete understanding of eyelid conformation and function of the patient and has properly planned his/her surgical technique. Evaluation and pre-surgical planning must be done prior to general anesthesia. A complete ophthalmic exam, with acquisition of the “minimal ophthalmic data base” (menace response, direct and consensual pupillary light reflex, palpebral reflex, Schirmer tear test, fluorescein stain, and tonometry) should be acquired in any patient presenting with an eyelid disorder. There are general “trends” in eyelid diseases that are important to be aware of even prior to examining a small animal patient. For example, the combination of ptosis and entropion of the upper eyelid is commonly seen in breeds with abundant forehead skin folds. Treatment options include surgical reduction of skin folds, suspending the brows, enforced secondary granulation of the upper eyelid, or a combination of procedures. Lid-shortening procedures reduce corneal exposure, improve functional blinking, and reduce likelihood of traumatic proptosis.

In some dog breeds with a broad skull base and redundant fascial skin, it is not uncommon to diagnose an involuted lateral canthus with entropion and in such cases, surgical correction of this eyelid abnormality may be by application of traction to the lateral canthus, or by resection of the lateral canthal ligament. A combination of entropion, ectropion, and macroblepharon may result in the presence of diamond shaped eyelids (e.g., the Clumber Spaniel) and indeed may even be considered “standard for the breed” in some cases. Surgical correction of this type of highly involved eyelid abnormality may involve the combination of several procedures and referral to a board-certified ophthalmologist may be warranted. Careful consultation with the owner is also essential as many do not wish to permanently alter the “diamond eye” appearance. The purpose of this lecture (and the next) will be to aid the small animal practitioner in proper surgical preparation, ensure the correct diagnosis of various eyelid abnormalities, choose the most appropriate surgical repair, and provide the practitioner with some guidelines concerning referral.

General Therapeutic Considerations for Adnexal Surgery

Most corrective eyelid surgeries require general anesthesia. A thorough physical examination with appropriate pre-operative bloodwork is indicated especially in middle-aged to older dogs. When corrective eyelid surgery is planned to remove an eyelid mass, a more complete pre-surgical work-up is often indicated (for example, FNA or small incisional biopsy if a malignancy is suspected to plan for adequate surgical margins, thoracic radiographs to look for evidence of lung metastasis, lymph node aspirates). The majority of canine eyelid masses are benign (e.g., sebaceous adenomas, papillomas, histiocytomas), however, feline eyelid masses are not as common in practice and are more likely to be malignant (e.g., squamous cell carcinoma, basal cell carcinoma). In this author’s opinion, any eyelid mass removed from a dog or a cat should be submitted for histopathologic evaluation. Malignant eyelid tumors may require additional surgery or ancillary treatment. Proper head position is important to successful surgical outcome and may be facilitated with sandbags or surgical vacuum packs. Careful surgical planning to avoid over-correction is essential. For example, entropion or eyelid agenesis may be complicated by distichiasis, trichiasis, and/or corneal ulceration, further exacerbating the primary eyelid abnormality. Postoperative use of an E-collar is usually necessary to prevent patient rubbing and premature wound dehiscence. If the patient is evaluated a few days or weeks before surgery is planned, this author finds it helpful to teach owners how to train dogs to wear an E-collar prior to surgery, making the postoperative period less stressful for both owner and pet.

The eyelids are highly vascular. With proper pre-operative planning, surgical technique, and postoperative care, most corrective eyelid procedures carry a favorable prognostic outcome. Care must be taken to avoid over-correction of an eyelid abnormality. Meticulous anatomic repair of wounds at the eyelid margin is critical to the preservation of corneal clarity. These details will be discussed in the second half of this two-part lecture series.

Patient Preparation

This will be discussed in more detail during the lecture. In general, this author prefers minimal clipping when possible and a dilute betadine solution (1:20 to 1:50) to prepare the globe, conjunctiva, and surrounding periocular area for ophthalmic surgery. Briefly: most patients are treated pre-operatively with an NSAID (e.g., carprofen or meloxicam) to minimize intra- and postoperative wound swelling. The use of peri-operative systemic antibiotics may be indicated in some patients. Anesthesia for eyelid surgery is usually routine. After induction, KY-Jelly® may be placed into the conjunctival sac whilst the hair is clipped. For patients with concurrent corneal wounds (non-penetrating) sterile KY-Jelly® in sachets can be used. Lashes are trimmed with scissors coated in KY-Jelly® to collect the hairs immediately. Care is taken to minimally traumatize the periocular skin with clipping to reduce the risk of inducing ‘clipper rash’ - which could lead the patient to self-traumatize the surgical area. In some breeds, it is preferable not to aim for a ‘close’ clip, as this would cause excessive skin damage - such as in the Boxer, the Cocker Spaniel, or the Shar Pei.

The clipped hair can be removed from the periocular area with a combination of careful use of a vacuum cleaner and a sticky roller designed to remove hair from clothes. Sellotape can also be used to remove minor remaining hair clippings. For the eyelid surgeries described below, the patient is placed in lateral recumbency and the head is elevated and brought in a horizontal position with the help of a deflatable vacuum bag (‘buster bag’).

The ocular surface, conjunctival sacs and eyelids are prepared in a way that is not damaging to the corneal surface. A dilute Povidone-iodine solution is used; when preparing this it is of utmost importance that Povidone stock solution is chosen and not the scrub (the later contains detergents that are toxic to the corneal epithelium).

The dilution is prepared as follows:

• 1/50 dilution is used for cornea and conjunctiva
• 10 ml stock Povidone-iodine 10% into 490 ml saline 0.9%
• 1/10 dilution is used for the periorbital skin
• 0 ml stock Povidone-iodine 10% in 450 ml saline 0.9%

The eye and conjunctival fornices are initially gently wiped clean with a sterile cotton-tipped applicator to remove the KY-Jelly®. The eye is then flushed 3–5 times with 10 ml of the 1/10 Povidone-iodine solution; care is taken to flush behind the third eyelid and into the conjunctival fornices. In order to facilitate the flushing, a soft/plastic naso-lacrimal cannula can be applied to the syringe containing the flushing solution. The periocular skin is gently wiped 3–5 x for both upper and lower lid with the 1/50 dilution. Preparation of the eye for surgery is completed with a final flush with sterile saline. For surgery, the eye is draped with a sterile surgical cloth that has an adequate ‘window’. Both the use of re-usable drapes and of single use drapes is possible.

Adnexal Surgical Instrumentation and Suture Material

Commercially available ocular instruments are designed to minimize trauma to adnexal structures and facilitate handling of small needles and suture material. This author suggests that the basic eyelid ocular surgical pack should contain the following instruments:

• Barraquer eyelid speculum
• Hartman curved hemostatic mosquito forceps
• Knapp curved strabismus scissors
• Stevens straight tenotomy scissors
• Bishop-Harmon straight tissue forceps
• Small Derf needle holder
• Bard-Parker scalpel handle that accommodates a number 15 Bard-Parker scalpel blade
• Berke-Jaeger eyelid plate
• Desmarres chalazion forceps

Ophthalmic instruments are delicate and should be cleaned with care, fine tips covered with plastic tip covers, and steam-autoclaved in a dedicated protective instrument tray.

Adnexal Suture Material

1.  Nonabsorbable (silk, nylon, polypropylene, and braided polyester) and absorbable (polyglycolic acid, polyglyconate, and polydioxanone) suture material are commonly used in adnexal surgery. Of the commercially available options, this author prefers the use of suture material that is flexible and has less memory [e.g., silk (Ethicon) or braided nylon (Nurolon - Ethicon) versus monofilament nylon (Ethilon - Ethicon) for nonabsorbable suture and braided polyglactin 910 (Vicryl - Ethicon) versus monofilament polydioxanone (PDS II - Ethicon)] when performing eyelid surgery. Synthetic absorbable sutures have prolonged tensile strength and, therefore, can be used as a substitute for non-absorbable suture in many eyelid surgical procedures. Removal in 10–14 days is still recommended when using absorbable suture in the skin to minimize tissue reaction and expedite healing. Polyglactin 910 and polyglycolic cid are most commonly used in cutaneous and conjunctival eyelid tissues because they are softer, more pliant, and nonantigenic, thereby causing minimal tissue reactions. Coated polyglactin 910 decreases tissue drag; however, knots must be secure to prevent premature loosening. Suture size is dependent on the procedure but typically ranges from 6–0 to 4–0 for most adnexal surgeries in canine and feline patients.

2.  Needle type: Swaged needles result in smaller puncture holes though eyelid tissues, less tissue drag, and are recommended. Cutting or reverse cutting (1/4–3/8 circle type) are preferred. Tapered needles should be avoided unless repairing a prolapsed gland of the third eyelid, in which case tapered needles can be a useful adjunct.

3.  Other: Stents, made from pieces of IV tubing or sterilized rubber bands, help protect the eyelid skin and prevent premature dehiscence of sutures.

Acknowledgements

The author graciously appreciates contributions to these lecture notes by fellow colleagues, especially Dr. Christine Heinrich.

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