The lids are extremely important to the health of the ocular surface and function not only to protect against trauma, but also to provide for the distribution of the tear film over the eye. It is therefore important that disease of the eyelids be controlled before significant scarring interferes with their function. Structural eyelid defects should be corrected with procedures that return the anatomy to as close to normal as possible. Because the majority of the lid consists of skin, inflammatory diseases of the lids may be managed much as they would be for the skin. In the short time we have in this session, we will seek to focus on the most important structural defects of the lids and the methods that can be commonly employed to correct them.
The skin of the eyelids is relatively thin and pliable when compared to the skin elsewhere on the body. Because the tarsal plate of the eyelid of many of animals is less well developed than in man, the lid margins are extremely important for maintaining the normal shape and function of the palpebral fissure. In addition, the meibomian or tarsal glands empty through small openings that run the length of the middle of the lid margin and the lipid secretion of these glands is important for preservation of the tear film. Therefore, one of the important considerations in diseases and surgery of the eyelids is the maintenance of the integrity of the lid margins whenever possible.
The orbicularis oculi muscle encircles the palpebral fissure and functions to close the fissure when it contracts. The medial palpebral ligament and the retractor anguli oculi lateralis muscle function to anchor the orbicularis medially and laterally respectively. These medial and lateral attachments serve to preserve the elliptical shape of the palpebral fissure. They further prevent the fissure from becoming circular during contracture of the orbicularis for blinking and lid closure. In addition, the orbicularis oculi has fibers that insert into the lateral wall of the lacrimal sac, and contracture and relaxation of the fibers contribute to movement of tears through the sac via the so-called lacrimal pump.
When blinking occurs, the upper lid is more mobile and travels a greater distance over the cornea than the lower lid. In addition, because the lower lid naturally tends to sag slightly away from the globe, mild entropion and trichiasis are better tolerated when they affect the lower lid than the upper. The upper lid should thus receive a higher priority in reconstructive procedures and special attention should be directed toward maintaining the upper lid margin and conformation.
The major blood supply of the lids arises from the medial and lateral canthi. Therefore, care must be taken in surgery to assure the blood supply to the lids is maintained. When flaps are fashioned from the lids in reconstructive surgeries, their medial or lateral pedicles should be at least 4–6 mm in width to ensure that the flaps have adequate perfusion.
The lacrimal punctae and canaliculi function to drain the tears into the lacrimal sac and the lower punctum is more important than the upper in this function. Preservation of at least the lower punctum and canaliculus is thus a high priority in lid surgeries that involve the medial canthus.
A general rule of thumb is that defects involving up to 25% of the lid margin may be closed primarily. In some breeds with euryblepharon (macroblepharon) and ectropion, this percentage can be as much as 33%. As we will discuss, this can be extremely important in managing large lid defects and neoplasms.
BASIC SURGICAL PRINCIPLES
As with all things, difficult problems can often be solved by breaking them down into simpler tasks or steps. Several simple surgical techniques can be applied to the resolution of more difficult lid problems.
One question that often arises regards the age at which lid procedures should be performed when young animals have a lid defect (colobomas, entropion, ectropion, distichiasis, etc.). In general, the ideal situation would be to wait until at least a year of age when most of the maturation of facial conformation has occurred. However, the potential for secondary damage to the ocular surface must take precedence above all else, and any measure necessary should be taken to prevent corneal ulceration and/or scarring. Thus, the more severe the lid defect is the greater is the need for prompt surgical intervention.
Often the clinician is confronted with tumors or defects that involve the lid margin. The use of a cruciate suture (preferably 6-0 polypropylene or nylon) assures optimal closure of lid margin defects with elimination of tissue shifting without risk of corneal irritation from the suture knot.
When surgery or lacerations affect the lacrimal canaliculi, reconstruction can be aided by the cannulation using silastic tubing. This can be facilitated by initial passage of a monofilament suture through the canaliculi or the nasolacrimal duct. The tubing may then be passed over the suture and pulled through the ducts as discussed in the lecture. A “pigtail” probe may be used with great benefit, especially when cannulating the canaliculi. The use of this instrument and its limitations will be discussed.
In veterinary medicine, we have a tendency to want to do everything at once to accomplish correction during one surgery and avoid multiple anesthesias. However, the surgeon should remember that it is always easier to remove more tissue than it is to replace what is lost. In plastic surgery, it may be better to achieve correction through several gradual corrections than to risk over correction and/or excessive scarring. The owner should be made aware that secondary adjustment procedures might be needed to achieve optimal results so thorough discussion of the problem with the owner is essential.
CORRECTION OF DISTICHIASIS
Numerous techniques have been advocated for the treatment of distichiasis with differences dependent heavily on surgeon preference, available equipment, and residency training in different areas. Obviously, cases in which the extra lashes are causing no problems require no treatment, and when epiphora is the only sign, every effort should be made to rule out other causes before treatment of distichiasis is undertaken. Techniques most often advocated include, simple eversion of the affected lid margin, electroepilation (especially when small numbers of lashes are present), cryoablation with and without excision of the lash follicles, and laser ablation of lash follicles. One consistent teaching among most authors is that the lid margins should not be split as advocated for the disease in humans. Such splitting of the margins weakens it and contributes to irregularities and scarring which may be severe. In addition, recurrence of offending lashes and/or subsequent trichiasis is common with lid splitting. Similarly, any technique should avoid excessive damage to the lid margins. The advantages and disadvantages of the most common therapies will be discussed.
CORRECTION OF LARGE EYELID DEFECTS
The correction of large eyelid defects regardless of their origin poses one of the most challenging surgeries that confront the ophthalmic surgeon. The most commonly employed techniques include advancement and rotational flaps (rhomboid and pedicle) from adjacent skin and cross lid flaps. The advancement and rotational flaps are easier to perform but do not allow reconstruction of the eyelid margin when an upper eyelid defect is present. The cross lid flap uses the lower lid margin to correct defects of the upper lid. However, such flaps are more complex to perform and require surgery in at least two stages. These alternatives and their advantages and disadvantages will be discussed in detail.
TECHNIQUES FOR CORRECTION OF MACROBLEPHARON
Macroblepharon can result in the presence of both entropion and ectropion in the same eye. Depending on the severity, several different approaches to therapy may be employed. In the lecture, we will consider selected cases that illustrate the different techniques ranging from simple canthal closure to rhomboid canthoplasty.
ALTERNATIVES FOR THE CORRECTION OF ECTROPION
Depending upon whether ectropion is primary and related to excessive lid length and/or lack of lid tone or secondary to scarring, different approaches to correction may be employed. For scarring, the Wharton-Jones (V to Y) blepharoplasty may be most preferred, but other cases are best treated by lid shortening and techniques to improve lid tone. These techniques and their indications will be illustrated as time allows.
ALTERNATIVES FOR THE CORRECTION OF ENTROPION
Correction of entropion is perhaps the most commonly taught lid surgery and is perhaps the simplest to perform. Shar Peis and breeds with heavy facial folds can present the clinician with challenging predicaments. We will discuss when simple lid tacking is indicated and when to apply more advanced techniques.