Diagnosis and Treatment of Entropion

The Normal Eyelid Margin

Understanding exactly how the eyelid sits against the eyeball is important for understanding cicatricial entropion. We take the eyelid margin for granted, but there is a very specific relationship between the mucosal tissues on the back of the lid and the keratinized skin on the lid margin. The next time you perform a slit lamp examination, start to become familiar with this eyelid margin anatomy. The normal eyelid margin is flat, ending at right angles anteriorly and posteriorly to form a long thin rectangle of tissue ( Figure 4.2 ). The most posterior aspect of the normal lid margin is the mucocutaneous junction . It is at this point that the mucosa of the palpebral conjunctiva stops and the keratinized skin of the eyelid margin begins. Look at several normal patients to see this junction. The next time you see a patient with cicatricial entropion, you may be able to appreciate the fact that the mucocutaneous junction moves forward as the eyelid margin inverts ( Box 4.2 ).

Just anterior to the mucocutaneous junction are the meibomian gland orifices extending out from the tarsal plate. By everting the eyelid during the slit lamp examination you can see the faint vertical lines of the meibomian glands visible in the tarsal plate. Anterior to the meibomian gland orifices is the gray line . Initially, this line was thought to result from the fusion of the anterior and posterior lamellae. In reality, the gray line is a specialized muscle of the pretarsal orbicularis, known as the muscle of Riolan. The gray line is still used as a landmark to surgically separate the anterior and posterior lamellae of the eyelid in some procedures. Posterior to the gray line is the posterior lamella (the tarsus and the conjunctiva). Anterior to the gray line is the anterior lamella (the skin and muscle). The eyelashes arise anterior to the gray line, usually in one or two irregular rows in the lower lid and three or four irregular rows in the upper lid. The eyelash follicles originate on the surface of the tarsal plate. Learn these subtle anatomic features of the eyelid. They are especially important when you are evaluating patients with mild cicatricial entropion or trichiasis. I emphasize the changes that occur in the lid margin later in this chapter and more completely in Chapter 5 .

The Stable Lower Eyelid

Let’s go over the anatomic factors that are important for understanding and treating entropion. Remind yourself of the layers of the lower eyelid inferior to the tarsal plate (see Figure 2.35 ). Starting at a point below the tarsus from anterior to posterior, the layers of the eyelid are:

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  Skin

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  Orbicularis muscle

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  Septum

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  Preaponeurotic fat (the landmark for the lower lid retractors)

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  Retractors

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  Conjunctiva

The lid margin remains normally apposed to the eye during eye movements through a combination of forces holding the lid in position. Watch the lid during the slit lamp examination as the eye moves up and down. The pretarsal eyelid and the eyelid margin move as a unit. Remember that the pretarsal orbicularis is firmly adherent to the anterior surface of the tarsus, creating a block of tissue. The mucocutaneous junction of the eyelid margin does not change its position relative to the eyeball as the eye rotates ( Figure 4.3 ) . This is one of many aspects of our functional anatomy that we take for granted. When you try to reconstruct a missing eyelid margin, you come to appreciate this even more!

Several factors contribute to the stability of the lid. In general, a tight lower eyelid, without horizontal lid laxity, is a stable lid. Laxity predisposes the lower lid to either ectropion or entropion , as we have seen in Chapter 3 . Think about what the lower eyelid retractors do. As the eye looks down, the lower lid retractors pull the lower eyelid downward. If the retractors did not work in synchrony with the eyeball, the eyelid would block the pupil in downgaze. This synchronous movement results from the connection of the capsulopalpebral fascia portion of the lower eyelid retractors with the inferior rectus muscle.

The lower eyelid retractors also help to keep the eyelid margin in normal position. The retractors pull the lower margin of the tarsus inferiorly and posteriorly, in the direction of the pull of the inferior rectus muscle. This keeps the lower edge of the tarsal plate tucked in against the eye with the eyelid margin in the normal position. Normal tension on the lower eyelid retractors is essential for maintaining a stable eyelid and preventing entropion ( Box 4.3 ).

In the normal eyelid, the anterior and posterior lamellar tissues superior to the tarsus have enough redundancy and flexibility so that normal movement does not alter the position of the lid margin. There is no pull or cicatricial force turning the eyelid inward or outward.

Involutional Entropion

Involutional entropion occurs only in the lower lid. Three anatomic factors play a role in involutional entropion:

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  Laxity of lower eyelid retractors

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  Horizontal lid laxity

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  Overriding preseptal orbicularis muscle

Laxity of the lower lid retractors is the primary cause of involutional entropion ( Figure 4.4 ). Lower lid horizontal laxity is usually present, making the lid unstable. Laxity of the lower lid retractors allows the inferior edge of the tarsus to rotate away from the eye. This allows the lid margin to invert ( Figure 4.5 ). In many cases, the preseptal orbicularis muscle actually seems to push the lower eyelid margin inward. Variations of Figure 4.4 are shown in all texts discussing entropion. Make sure that you understand this figure. Later in this chapter you learn that you can often elicit involutional entropion by having the patient squeeze the eyelids closed tightly for a few seconds. This squeezing pushes the preseptal and orbital orbicularis muscle upward, initiating the inversion of the eyelid.

For many years, enophthalmos was considered to be an etiologic factor in involutional entropion. This has been disproven. The presence of enophthalmos has been shown to be no different in age-matched patients with or without entropion.

As an aside, many older patients have the appearance of small eyes. This is caused by a narrowing of the eyelid aperture both vertically and horizontally. As the retractors relax with age, the position of the lower eyelid elevates a bit. This upside-down ptosis of the lower eyelid is common in elderly patients with entropion. The upper eyelid becomes somewhat ptotic. The horizontal length of the palpebral aperture decreases, and the canthi become rounded as the canthal tendons lengthen; this condition is known as phimosis of the aperture. Look for this in your elderly patients. It is an apparent, but unappreciated, feature of aging. When you lift the upper eyelids and re-create the sharp lateral canthal angle with a lid-tightening procedure, you notice that the patient’s eyes (and face) look younger.

Spastic Entropion

Spastic entropion occurs when the eyelids are held in a closed or “guarded” position. The sustained squinting of the lower lid is the initiating force for the entropion. The most common situation for this reflex blepharospasm is after surgery, usually an anterior segment trauma repair or an extensive posterior segment procedure. The spasm or squeezing of the lid seems to push the lid margin against the eye. This condition most often occurs in patients who have predisposing factors to involutional entropion, such as horizontal laxity and lax lower lid retractors. The retractors cannot hold the lid in a normal position against the forceful overriding orbicularis pushing the lid margin inward.

Cicatricial Entropion

Cicatricial entropion is caused by shortening of the posterior lamella, which pulls the eyelid margin inward ( Figure 4.6 ). Cicatricial entropion is common throughout the world, especially where trachoma is endemic. Cicatricial entropion is less common than involutional entropion, but it is still seen in the United States. Any problem that causes scarring of the conjunctiva may cause a cicatricial entropion ( Box 4.4 ). Common causes include:

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  Ocular cicatricial pemphigoid

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  Alkali or acid burns

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  Surgical or accidental trauma

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  Recurrent chalazia or blepharitis

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  Stevens–Johnson syndrome

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  Trachoma

In most patients with cicatricial entropion, the conjunctival scarring is easy to see and the etiology is obvious ( Figure 4.7 ). As I said earlier, all instances of upper lid entropion are cicatricial. There is no upper lid involutional entropion.