Horizontal eyelid laxity

The tarsal plates are attached to the bony orbital rims by the lateral and medial canthal tendons. Lengthening of the tendons occurs with age. This increase in the horizontal length of the eyelid is responsible for the eyelid laxity that causes involutional ectropion. The tarsal plates do not lengthen with time. The insertion of the lateral canthal tendon is on the inner aspect of the lateral orbital rim at Whitnall’s tubercle. This slightly elevated area of the lateral orbital rim is approximately 10 mm inferior to the frontozygomatic suture. Remember when you reattach the lateral canthal tendon using the lateral tarsal strip procedure to place the tendon on the inner aspect of the rim to prevent lid distraction from the globe.

Midfacial hypoplasia

The bony architecture of the inferior orbital rim provides support for the lower eyelid. Individual and racial variations occur. Patients with higher cheekbones or prominent malar bones tend to have less ectropion. Asian patients tend to have a flat face with more prominent malar bones. Black patients tend to have less prominent malar bones. The bony architecture of white patients is intermediate. Patients with the so-called hypoplastic midface or maxilla have an inferior orbital rim that is somewhat posterior in relationship to the eyeball (Figure 3-2). These patients tend to have less support for the lower lid and may have lower lid retraction or ectropion. Another term for the hypoplastic maxilla is “hemiproptosis.” I like this term because it emphasizes the fact that the inferior half of the eye is more anterior than the orbital rim. Tightening of the lower lid in a patient with hemiproptosis may cause the eyelid to slide under the eye, so be careful in tightening any lower eyelid in a patient with hemiproptosis. The relationship of the maxilla to the inferior rim should be considered in patients undergoing lower eyelid blepharoplasty in order to avoid the common complication of eyelid retraction or “rounding” of the lower eyelid. You will see later that the term “hemiproptosis” is also referred to as a “negative vector” eyelid, especially in the context of lower eyelid cosmetic surgery.

Figure 3-2 “Hemiproptosis” or hypoplastic midface associated with lid retraction. Facial nerve paralysis after parotidectomy. (A) Note lower eyelid retraction on both sides and ectropion of right lower eyelid. (B) Inferior orbital rim is posterior to the front of the globe which complicates ectropion repair. (C) Note lower lid retraction in a second patient with hemiproptosis. (D) Simulated horizontal tightening of the lower eyelid increases the retraction.

Anterior lamellar shortening

The skin, orbicularis muscle, and orbital septum are normally flexible enough that spontaneous movement of the eyelids can occur. You are already familiar with the terms anterior lamella (skin and muscle) and posterior lamella (tarsus and conjunctiva). Scarring of the anterior lamella can cause a cicatricial ectropion (Figure 3-3). Lengthening of the shortened lamella by adding a full-thickness skin graft is the treatment for cicatricial ectropion. As you know, scarring of the posterior lamella also causes a cicatricial entropion.

Figure 3-3 Cicatricial ectropion caused by anterior lamellar shortening. (A) Trauma to the skin over the zygoma, resulting in a scar that pulls the eyelid down. (B) Chronic sun-damaged skin causing a generalized tightness of the facial skin. In both cases, surgical correction requires lengthening of the anterior lamella, usually with a full-thickness skin graft and lower eyelid tightening.

Middle lamella

Recently, the term middle lamella has been used to describe the tissues between the anterior and posterior lamellae of the eyelid inferior to the tarsal plate. These tissues include the orbital septum, the preaponeurotic fat, and the lower lid retractors. Scarring of the middle lamella may tether the eyelid, which causes cicatricial ectropion, lid retraction, or even cicatricial entropion, depending on how the scar tissue forms. This middle lamella scarring occurs most commonly after eyelid trauma or surgery.

Paralysis of the orbicularis muscle

The resting tone of the orbicularis muscle supports the tarsal plate and canthal tendons, helping to support the lower eyelid in the normal position. In patients with paralytic ectropion, the resting tone of the orbicularis muscle is reduced or absent (Figure 3-4). Ectropion occurs primarily in older patients who have an underlying element of lid laxity. In younger patients with facial nerve palsy, ectropion generally does not occur because there is no underlying lid laxity.

Figure 3-4 Paralytic ectropion caused by right facial nerve palsy. Note the flattened nasolabial fold and brow ptosis accompanying the ectropion.

Normal lid position and function are necessary for tear drainage. Any type of ectropion may cause tearing as a result of reflex tearing, punctal eversion, or loss of the lacrimal pump. Interestingly, many older patients with ectropion do not complain of tearing. This is probably because tear production decreases with age.

Etiologic factors

Are cicatricial changes present?

The etiology of the ectropion is usually apparent. The first question to ask is Is the ectropion cicatricial? Is there scar tissue pulling the eyelid away from the eyeball? Look for any specific scarring of the periocular area that would indicate previous accidental or surgical trauma. Look to see if the patient has tight skin on the whole face. Some patients, despite their age, may have tight skin with very few wrinkles. These patients may have generalized skin shrinkage as a cause of the cicatricial ectropion. Cicatricial ectropion is less common than involutional ectropion (see Figure 3-3).

Is there facial asymmetry?

If there are no cicatricial changes, ask the question, Is there evidence of facial asymmetry suggesting paralytic ectropion? Patients with facial nerve palsy have associated flattening of the nasolabial fold and coexisting brow ptosis. Patients with paralytic ectropion have significant laxity of the involved lower eyelid. Be sure to check for evidence of corneal exposure that would require additional medical or surgical treatment aside from repair of the paralytic ectropion (Figure 3-4). The additional procedures used in the management of facial nerve palsy will be covered in Chapter 9.

The eyelid distraction test

The eyelid distraction test is performed by manually pulling the eyelid away from the eyeball. The lower lid should not move more than 6 mm off the eyeball (Figure 3-6).

Figure 3-6 The eyelid distraction test to measure horizontal eyelid laxity. The eyelid should not pull away from the globe more than 6 mm.

The eyelid snap test

The eyelid snap test is performed by pulling the lower eyelid inferiorly toward the inferior orbital rim. An eyelid without lower eyelid laxity will spring back into position without a blink. The lax lower eyelid will remain away from the eye for a period of time. The amount of laxity can be grossly quantified by asking the patient to blink and counting the number of blinks required to return the lid to normal position. I note in the chart something like, “eyelid returns with two blinks.” You will find the eyelid distraction and eyelid snap tests very helpful (Figure 3-7). The amount of laxity is directly related to the treatment—shortening the eyelid with a lateral tarsal strip operation. Remember that involutional ectropion is one of the most common oculoplastic conditions you will see.

Figure 3-7 The eyelid snap test to measure horizontal lower eyelid laxity. (A) The eyelid at rest. (B) The lower eyelids manually retracted. (C) The normal eyelid should return to normal position in one blink. In this case, the eyelids do not return to normal with several blinks.