Normal eyelid position

The upper lid rests at or just below the upper limbus. The lower lid normally sits at the lower limbus. The palpebral aperture is the distance between the upper lid margin and the lower lid margin. The normal measurement is approximately 9 mm. The position of the upper lid is best quantified as the upper lid margin reflex distance (MRD₁). This measurement extends from the central corneal light reflex to the upper lid margin and is normally 4–5 mm (Figure 8-1).

Figure 8-1 Measurement of the margin reflex distance (MRD) and the palpebral fissure. The MRD₁ is 1 mm. Often an estimate will suffice, 1–2 mm, in this case. The MRD₂ is 5 mm. The palpebral fissure is the sum of the MRD₁ and the MRD₂.

The upper eyelid retractors

The retractors open the upper eyelid. The retractors are:

Functional or anatomic abnormalities in the levator muscle complex are the cause of most ptosis.

The levator muscle

The levator muscle is the primary retractor of the upper eyelid. This skeletal muscle is responsible for voluntary elevation of the upper eyelid. Innervation to the levator muscle is via the superior division of the third cranial nerve (the oculomotor nerve). The levator muscle originates at the orbital apex and extends forward inferior to the bone of the orbital roof (Figure 8-2). At the orbital aperture, the levator is supported by Whitnall’s ligament (see Figure 2-22). As the levator muscle travels anteriorly, it becomes a fibrous aponeurosis that extends inferiorly into the eyelid to insert on the anterior aspect of the tarsal plate. Fibrous extensions of the aponeurosis pass through the orbicularis muscle to create the upper eyelid skin crease (Figure 8-3).

Figure 8-2 The levator complex: levator aponeurosis, Whitnall’s ligament, and levator muscle.

Figure 8-3 Cross-section of the upper eyelid.

Whitnall’s ligament is an important anatomic landmark. The ligament extends from the fascia surrounding the lacrimal gland temporally to the trochlea medially. Whitnall’s ligament is usually easy to see intraoperatively as a strong white band of fibrous tissue. Generally the tissue superior to the ligament is muscle and the tissue inferior to the ligament is aponeurosis, although variation exists among individuals. It has been suggested that Whitnall’s ligament serves as a “pulley” for the levator muscle. Although the levator muscle complex does not slide through the ligament, the concept of the ligament allowing the muscle to change direction is a helpful one.

As the levator aponeurosis travels from Whitnall’s ligament to the tarsus, it “fans” out to form the horns of the levator aponeurosis. The horns are the medial and lateral flared extensions of the aponeurosis inserting into the medial and lateral canthal regions. During operations on the levator, you will see that the lateral horn of the aponeurosis is much thicker and stronger than the medial horn. The lateral horn is cut, or released from the lateral orbital rim, to improve the typical temporal flare of Graves disease upper eyelid retraction.

Müller’s muscle

Müller’s muscle is responsible for the involuntary upper eyelid elevation seen in the sympathetically innervated “fight or flight” phenomenon. Müller’s muscle is “sandwiched” between the conjunctiva posteriorly and the levator aponeurosis anteriorly. Müller’s muscle extends from the superior margin of the upper tarsal plate to the level of Whitnall’s ligament (Figure 8-3). A prominent surgical landmark on the surface of Müller’s muscle is the peripheral arcade, a vascular arcade extending across the muscle a few millimeters above the tarsal plate (Figure 8-4; see also Figure 2-23). You will recall that the loss of innervation to Müller’s muscle results in the mild ptosis associated with Horner’s syndrome.

Figure 8-4 The peripheral vascular arcade in Müller’s muscle. Note the line of the surgically disinserted levator aponeurosis.

The frontalis muscle

No doubt you have patients with drooping upper lids who lift their eyebrows to provide a tiny bit more upper eyelid elevation. The frontalis muscle lifts the brows and is a weak retractor of the upper eyelids (Figure 8-5). The frontalis muscle is part of the galea aponeurotica of the scalp. The fibrous aponeurosis extending from the occiput becomes the frontalis muscle inferior to the hairline. Like the other muscles of facial expression, the frontalis muscle is innervated by a branch of the facial nerve, the frontal nerve (see Figure 2-27). Elevation of the eyebrows and prominent forehead furrows seen in a patient with ptosis tell you that the drooping lids are interfering with the patient’s vision. In some patients, a brow ache will occur with extended brow activity. The action of the frontalis muscle should be “blocked” with your thumb when making measurements of the eyelids.

Figure 8-5 The frontalis muscle is a weak elevator of the eyelid.

The “eyelid vital signs”

The condition or “health” of the eyelid can be identified by measuring the eyelid vital signs:

We have already mentioned the MRD as a simple way to measure the height of the upper lid. The most practical measure of the strength of the levator muscle is the levator function. The levator function is defined as the excursion of the upper lid from extreme downgaze to extreme upgaze measured in millimeters. This movement is normally 15 mm. You will recall that the upper eyelid skin crease is created by the pull of the levator aponeurosis on the skin. The skin crease height is the distance from the lid margin to the crease. This height varies among individuals, but averages 6–8 mm for men and 8–10 mm for women at the highest point. The crease slopes both medially and laterally. A weak levator muscle creates less pull on the skin so the crease is less distinct or “weak.” Read this paragraph again.

The vital signs will give you the information that you need to know to classify and treat ptosis. You will see the following concepts repeated several times in this chapter:

Notice how important the levator function is. As you become experienced in taking care of patients with ptosis, you will see that asking “What is the levator function?” becomes the critical question (Box 8-1). We will discuss this further in the next section.

A simplified system

There are many types of ptosis and many systems that classify the types (Box 8-2). From a practical point of view, most patients you will see have either simple congenital ptosis or involutional ptosis. Most of the children you will see have simple congenital ptosis. Most of the older adults you will see have an involutional ptosis. I group the other less common types into the category unusual ptosis. This is an oversimplification, but it works well.

The levator function: the relationship to classification

For this approach to work, you must learn the common types of ptosis well. Most of our medical training is spent learning the details of diseases that we will rarely see, an example being ptosis secondary to myasthenia gravis. For now, I will be emphasizing the two common types of ptosis. After you know all about these two types, you will be able to easily identify an unusual type of ptosis when you see something that doesn’t fit with the two common types.

Levator function is the key concept in ptosis classification and treatment. We have already stated that levator function is defined as the movement, or excursion, of the eyelid from extreme downgaze to extreme upgaze. It is measured in millimeters with 15 mm being the average normal adult measurement (Figure 8-6). The levator function is the most clinically useful indicator of the health of the levator muscle. Normal movement suggests that the levator muscle has normal strength (Box 8-3). As we have said, the levator function forms the basis of both classification and treatment of ptosis. Does the patient have “normal” levator function? Is the levator function reduced? Is it poor or absent?

Figure 8-6 Measurement of the levator function. Note the position of the thumb on the brow, preventing any eyelid elevation by the frontalis muscle. (A) Eyelid in extreme downgaze. (B) Eyelid in extreme upgaze. The excursion of the eyelid, or levator function, is 15 mm in this case.

Simple congenital ptosis is always associated with reduced levator function. If you see a child with ptosis and normal levator function, something doesn’t make sense, and you should consider another diagnosis. Involutional ptosis is associated with normal (or near normal function). If you see an adult with ptosis and reduced levator function, something doesn’t make sense, and you should consider another diagnosis. Are you getting the idea? So far, we know that:

When I see a patient with ptosis, I classify the ptosis into one of these three categories. Most patients will have involutional or simple congenital ptosis. Congenital ptosis is much less common than the acquired forms of ptosis; consequently, the majority of patients will have involutional ptosis.

Tips for measuring the levator function

As you measure the levator function, you must immobilize the eyebrow so that the action of the frontalis muscle is eliminated completely. The amount of movement is measured with a millimeter ruler placed next to the patient’s eye. The measurement is straightforward with adults, but may be difficult with children who will often elevate the chin as well as the eyes. It is sometimes helpful to practice a few times with the child before actually measuring the function. I will often demonstrate on myself to give the child the idea. Using the example of a “rocket ship” blasting off will help to hold the child’s attention. Several measurements should be made until a reliable number can be obtained.

Watching how the lid crease develops with lid elevation will give a good idea of the function as well. As you get experience with measuring levator excursion, you will notice that the speed of elevation also varies among individuals. Later in the chapter, we will talk more about how levator function plays a role in treatment choice. At this point, we will discuss simple congenital ptosis and involutional ptosis in detail.

Simple congenital ptosis

Let’s start with some comments on nomenclature. Some classification systems include congenital and acquired ptosis as the major categories. This is appropriate in some ways. Obviously congenital ptosis means that the patient was born with a drooping lid, and acquired ptosis means that the ptosis developed after birth. Unfortunately, so many varied types of ptosis fit into these two categories that you are not given any direction for a treatment plan using this classification. To avoid confusion with the inclusive term congenital ptosis, I like to use the term simple congenital ptosis to describe a specific form of ptosis present at birth. For the most common form of acquired ptosis that occurs late in life, I like to use the term involutional ptosis (Box 8-4).

In simple congenital ptosis, the eyelid is ptotic because of a dystrophy of the levator muscle itself. I use the term simple to specify that the only problem is the dystrophic levator muscle. When you perform ptosis surgery on a patient with simple congenital ptosis, you will see that the dystrophic muscle is infiltrated with fatty tissue. The muscle is no longer a healthy red color, but yellowish to a variable degree (Figure 8-7). This weak muscle cannot move well so the levator function is reduced. Usually the degree of ptosis is related to the levator function, that is the lower the levator function, the more ptosis present. In patients with severe ptosis, the levator function may be totally absent. In patients with mild ptosis, the levator function may be minimally reduced.

Figure 8-7 Fatty infiltration into the levator muscle seen in simple congenital ptosis.

As alluded to above, reduced levator function is associated with a weak or absent skin crease. Remember that the skin crease is formed by attachments of the levator aponeurosis extending through the orbicularis to the skin at or near the top of the tarsal plate. If the levator is not pulling well, the skin crease will likewise not be as well defined.

Although we usually think of the upper lid not moving up well, it is probably more accurate to think of the weak and fibrotic muscle not moving well in either upgaze or downgaze. A characteristic of congenital ptosis demonstrating this is known as lid lag on downgaze (Figure 8-8).

Figure 8-8 Characteristics of simple congenital ptosis, in this case bilateral and asymmetric. (A) Ptotic right upper eyelid with a weak skin crease. (B) The upper eyelid does not drop as far on the less ptotic side (lid lag on downgaze) because of the fibrosis in the weak levator muscle. (C) The upper eyelid does not elevate well (reduced levator function).

Simple congenital ptosis ranges from mild to severe. In essentially all patients with congenital ptosis, the problem is bilateral. Sometimes, the amount of ptosis is quite asymmetric, and parents will only recognize that one side droops (see Figure 8-8). It is worth pointing out the bilaterality because it will probably affect some of the subtleties of the treatment.

Typically, simple congenital ptosis is associated with:

We have stressed that levator function is the key to both classification and treatment of ptosis. For simple ptosis with levator function greater than 4 mm, a levator aponeurosis advancement (tightening the levator) is the correct treatment. Greater amounts of advancement are necessary for diminishing amounts of function. If the levator function is less than 3 mm, a frontalis sling is appropriate. For levator function between 3 and 4 mm, a generous advancement is usual, with the resection extending high above Whitnall’s ligament into the muscle itself (Box 8-5).

Involutional ptosis

In contrast to simple congenital ptosis, involutional ptosis is associated with normal, or near normal, levator function. The traditional teaching says that the muscle is normal. The droop of the lid is suggested to be caused by the aponeurosis separating from the tarsal plate; hence, the commonly used name, aponeurotic ptosis. The term disinsertion is used, implying a slipping of the aponeurosis (disinsertion) off the tarsal plate or a thinning of the aponeurosis (dehiscence or rarefaction) itself. This pathophysiologic concept is helpful to differentiate this form of ptosis from the simple congenital form in which the muscle is weakened and much less easy to tighten surgically.

From a conceptual point of view, these features are helpful. Remember the suggested pathogenesis is that the aponeurosis is disinserted or stretched. The muscle is normal. It then makes sense that the levator function is normal. A high skin crease is the result of the levator fibers to the skin being dragged upward with the disinserted aponeurosis. The lid margin remains low throughout downgaze: lid drop on downgaze. This is caused by the eyelid being “longer” because of the aponeurosis disinsertion or stretching. Contrast this with the lid lag on downgaze in congenital ptosis caused by the fibrotic levator muscle.

Involutional ptosis ranges from mild to severe. It may be bilateral or unilateral. Usually there is an element of bilaterality to the ptosis if you look for it, although the patient often only complains about the more ptotic side.

Typically, involutional ptosis is associated with:

Compare the photos of the patients with simple congenital and involutional ptosis to get these points clear in your mind (Figure 8-9). Although not all patients show these features on examination, the concept is valuable. However, as we will discuss later, the etiology of involutional ptosis as being entirely “aponeurotic” is likely not accurate.

Figure 8-9 Characteristics of involutional ptosis. (A) Ptotic left upper eyelid with a high skin crease. (B) The upper eyelid shows lid drop on downgaze. (C) The levator function is normal.

Because patients with involutional ptosis have normal levator function, tightening the levator aponeurosis is the procedure of choice. You should notice that, as long as the levator function is good, levator aponeurosis advancement is the procedure of choice for both of the common types of ptosis.

Introduction

Your goal for the history taking and physical examination is to obtain three important pieces of information:

With the background you have so far, you know that most children will have simple congenital ptosis, and most adults will have an involutional type of ptosis. During the history taking and physical examination, you will look for findings that confirm the diagnosis. At the same time, you will be looking for factors that point away from the common diagnosis.

Once you have convinced yourself of the diagnosis, you will look for the factors that allow you to devise a treatment plan. You already know that the most important part of this is the levator function. Other factors may cause you to modify or individualize the treatment plan. Does the patient have a dry eye? Is closure incomplete? Does the normal lid have an unusual contour that you may need to match? Is the patient too frail to have an operation in the usual outpatient setting? There are many of these factors, and looking for them becomes second nature with experience.

Taking a history in children with ptosis

Is the diagnosis simple congenital ptosis? There are a few questions that you can ask to see if the child with ptosis has simple congenital ptosis. Remember that simple congenital ptosis involves only a ptotic upper lid in an otherwise healthy child with no other abnormal eye findings.

Is the ptosis congenital? When a ptosis is seen in a child, it is almost always congenital. Any onset after birth suggests a different diagnosis.

Is the ptosis unilateral or bilateral? Remember that congenital ptosis is usually bilateral, but often asymmetric. The parents may not have recognized this.

Does the lid change position? Is the lid ever open all the way? Does the lid position change with chewing or sucking?

Is there a family history of ptosis?

Taking a history in adults with ptosis

The goals of the history taking for an adult are the same as those for a child but are somewhat more involved because there are more unusual types of ptosis in adults. The goals are:

Is the diagnosis involutional ptosis? The first part of the history taking will help you determine if the ptosis is the usual involutional type of ptosis seen as the most common acquired ptosis in adults.

Is the ptosis acquired or has it been present since birth? When was the onset? What is the rate of progression?

Introduction

As we have seen above, a good history prepares you to do a directed physical examination. As in all fields of medicine, the history and physical examination are highly complementary. The goals of the physical examination are:

The eyelid vital signs give an assessment of the overall condition of the eyelids. Remember the eyelid vital signs:

You should measure the eyelid vital signs in every patient with ptosis.

The margin reflex distance

We used the term, margin reflex distance (MRD) earlier. The MRD is a useful measurement for describing the position of the eyelids. Before the introduction of the MRD, the palpebral fissure measurement was used. This distance is the millimeters measured between the upper and lower lids. A normal palpebral fissure is 9–10 mm. For the palpebral fissure measurement to be meaningful in describing the upper lid position, the lower lid must be in the normal position. A fissure of 9 mm could mean that the upper lid is crossing the pupil and that the lower lid is 4 mm below the lower limbus. For this reason, the palpebral fissure, or aperture, measurement has largely been replaced by the MRD measurement.

Useful refinements of the MRD measurement are the MRD₁ and MRD₂. MRD₁ designates the distance of the upper lid from the corneal light reflex. MRD₂ designates the distance of the lower lid from the corneal light reflex. These measurements give a good mental picture and accurately define the position of the upper and lower lids.

The MRD₁ measures the degree of ptosis. It should be measured using a penlight and a millimeter rule. With the patient at your eye level, ask him or her to look straight ahead at a distant target. Shine the penlight at the patient’s eye. The distance from the corneal light reflex to the upper lid margin, measured with the millimeter rule, is the MRD₁. With some experience, it is easy to estimate the MRD₁, if you assume that the corneal diameter is 10 mm and that the normal upper lid resting position is just below the upper limbus. The normal MRD₁ is between 4 and 5 mm. If the lid margin crosses the pupil, the MRD₁ is 0 mm. If the lid margin is about halfway down from the limbus to the corneal light reflex, the MRD₁ is 2.5 mm (a good number to remember because this is the MRD₁ often considered to indicate that a visual impairment exists) (Figure 8-10).

Figure 8-10 MRD and palpebral fissure measurements. Note that the palpebral fissures measure the same in examples (A and D) although each represents a different clinical condition. (A) Normal: MRD₁ of 4 mm, MRD₂ of 5 mm, and palpebral fissure of 9 mm. (B) Upper lid ptosis: MRD₁ of 2 mm, MRD₂ of 5 mm, and palpebral fissure of 7 mm. (C) Upper lid retraction: MRD₁ of 7 mm, MRD₂ of 5 mm, and palpebral fissure of 12 mm. (D) Upper lid ptosis and lower lid retraction: MRD₁ of 2 mm, MRD₂ of 7 mm and palpebral fissure of 9 mm.

It is important to remember that the patient should be relaxed during this measurement. The frontalis muscle should not be contributing to the lid opening. As we stated earlier, it is best to stabilize the brow during this measurement. Take care not to push the lid down. I usually ask the patient to close the eyes and then open them in a comfortable position. Often the patient will be somewhat anxious during the initial part of the examination, and the eyes will be open more than usual. It is important to recognize this and help the patient relax during this measurement.

With experience, it is easy to accurately estimate the MRD just by watching the patient while obtaining the history. Although for the sake of organizing this textbook, I have separated history taking and physical examination, as you probably already know, many observational measurements are made while obtaining the history. As you have probably heard before in your training, the physical examination starts when the patient walks into the examination room.

The levator function

Related posts:

The Diagnosis and Management of Misdirected Eyelashes The Art of the Surgical Technique Aesthetic Surgery of the Face Abnormal Movements of the Face Diagnosis of Malignant and Benign Lid Lesions Made Easy The Diagnostic Approach to the Patient with Proptosis

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