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Introduction
Entropion of the eyelid occurs when the lid margin inverts or turns against the eyeball ( Figure 4.1 ). The keratinized skin of the eyelid margin and eyelashes rub against the cornea and conjunctiva, causing irritation. Unlike with ectropion, the irritation is troublesome enough so that most patients seek medical treatment early. Entropion is common, but less common than ectropion of the lids.
There are four types of entropion ( Box 4.1 ). A congenital form of entropion exists, but it is so rare that it is hardly worth mentioning.
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Involutional
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Spastic
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Cicatricial
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Marginal
The anatomy of the lower eyelid is discussed as it relates to the causes of entropion in some detail. The two most important causes of involutional entropion are horizontal lid laxity and disinsertion or laxity of the lower eyelid retractors . As discussed in Chapter 3 , any horizontal laxity of the eyelid contributes to instability. Without the normal tension of the lower eyelid retractors pulling the lower edge of the tarsus inferiorly and posteriorly, the eyelid may invert, pulling skin and lashes against the eye. The concepts of anterior and posterior lamellar shortening are also important in the discussion of entropion. Scarring of the posterior lamella, conjunctiva, and tarsus causes a cicatricial entropion.
The history and physical examination show the etiology of entropion to be either lax tissues (seen with involutional and spastic entropion types) or shortening of the posterior lamellar tissues (seen with cicatricial and marginal entropion types). Lower eyelid entropion is most commonly involutional. The symptoms of irritation are intermittent , and lower eyelid horizontal laxity is seen. Upper eyelid entropion is always cicatricial and is a source of constant irritation. When you evert the lid, you see cicatricial changes. Cicatricial forms of lower lid entropion do occur, so it is important to look for scarring of the posterior lamella in the lower lid also. Spastic entropion occurs when the eye is irritated and inflamed. Guarding of the inflamed eye, with some squeezing of the eyelid, initiates the entropion. Usually, some elements of laxity are also present. Marginal entropion, a subtle form of eyelid inversion, is often perceived by the patient (and sometimes the inexperienced examiner) as an eyelash problem.
Involutional entropion is the most common type of entropion seen in the United States, so you should be familiar with its management. The aim of surgical treatment is to restore the normal tension of the lower lid retractors and to correct any coexisting horizontal lid laxity. The discussion includes the retractor reinsertion operation and the lateral tarsal strip operation to correct involutional entropion. Learn these operations well.
Cicatricial entropion is less common than involutional entropion. Trachoma is the “textbook” cause of posterior lamellar scarring that leads to cicatricial entropion. Trachoma is rarely seen in the United States. The typical trachoma patient with cicatricial entropion has severe conjunctival scarring with the eyelid margin inverted, causing skin and lashes to rub against the eye. Chemical, thermal, and conjunctival diseases can cause a cicatricial entropion. In reality, the patient with the most commonly seen type of cicatricial entropion has a mild form, called marginal entropion . The eyelid margin is turned in slightly, bringing the lashes against the eye. A considerable amount of time is spent on marginal entropion in Chapter 5 . The aim of treatment of all forms of cicatricial entropion is to restore the normal length of the posterior lamella using either incisional rotation of the margin or incision of the cicatrix and replacement with a graft. The tarsal fracture operation is a great margin rotation procedure to add to your list of competencies for repair of marginal entropion or mild degrees of cicatricial entropion of the lower eyelid. The anterior lamellar advancement procedure is also an upper eyelid everting procedure that pulls the anterior lamella tighter. When the entropion is too severe for incisional rotation, mucous membrane grafts are necessary. You should learn to recognize patients with severe entropion who need the more advanced operations involving grafting. These grafts are not often needed, however.
Spastic entropion is an unusual form of eyelid entropion. You occasionally see this form of entropion occurring with squeezing of the lids in association with ocular pain or inflammation, often after eye surgery. Frequently, the entropion resolves as the postoperative discomfort disappears. If corneal irritation is severe, treatment with Quickert sutures returns the lid to its normal position. There are not many patients with spastic entropion. Quickert sutures are easy to learn, however, and are an easy solution for spastic entropion when it occurs.
Anatomic Considerations
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 ).
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Mucocutaneous junction
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Meibomian gland orifices
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Gray line
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Eyelashes
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 ).
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Appropriate horizontal tension of the lower lid so that the eyelid is apposed to the eyeball
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Lower lid retractors applying appropriate tension to the inferior margin of the tarsus, pulling the lower edge of the tarsus inferiorly and posteriorly and thus preventing the lid margin from turning inward toward the eye
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Synchronous movement of the inferior rectus and lower lid retractors so that the eyelid moves downward as the eye travels in downgaze
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Balance between the anterior and posterior lamellar tension
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
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Laxity of lower lid retractors
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Horizontal lid laxity
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Overriding preseptal orbicularis muscle
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.
Marginal Entropion
Patients with cicatricial entropion have eyelashes against the eye. The problem is classified as entropion, not trichiasis, because the eyelid margin is obviously inverted. Most patients diagnosed with trichiasis have a subtle form of cicatricial entropion known as marginal entropion . Slit lamp examination of these patients shows that the lid margin is no longer a flat platform with well-defined right-angled anterior and posterior edges. The posterior angle of the lid margin has a slightly rolled appearance, with the mucocutaneous junction being more anterior than normal. There may be subtle scarring or inflammation of the posterior surface of the conjunctiva and tarsus. This subtle shortening brings the eyelashes against the cornea. The diagnosis and management of marginal entropion is discussed in the next chapter. This is an important concept, so do not ignore it.
At this point you should:
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Understand the definition of entropion
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Be able to recognize entropion in a patient
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Know the normal anatomic appearance of the eyelid margin as seen with the slit lamp (this is very important in understanding trichiasis)
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Know the anatomic factors responsible for a stable eyelid
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Understand the anatomic factors responsible for
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Involutional entropion
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Cicatricial entropion
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