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Chapter 82 – Clinical Anatomy of the Eyelids

Chapter 82 – Clinical Anatomy of the Eyelids

 

JONATHAN J. DUTTON

 

 

 

 

 

DEFINITION

• The eyelids are mobile, flexible, multilamellar structures that cover the globe anteriorly.

 

KEY FEATURES

• The eyelids provide protection from desiccation and airborne foreign matter.

• The eyelids anatomically contain both superficial musculocutaneous elements anteriorly and orbital components posteriorly.

 

 

 

INTRODUCTION

The eyelids serve a vital function by protecting the globe. They provide important elements of the precorneal tear film and help distribute the tear film evenly over the surface of the eye. The eyelids collect tears and propel them to the medial canthus, where they enter the lacrimal drainage system. The eyelashes sweep airborne particles from the front of the eye, and the constant voluntary and reflex movements of the eyelids protect the cornea from injury and glare.

ANATOMY OF THE EYELIDS

In young adults the interpalpebral fissure measures 10–11?mm vertically. With advancing age this decreases to only about 8–10?mm. [1] The horizontal length of the fissure is 30–31?mm. The upper and lower eyelids meet at an angle of approximately 60° medially and laterally. In primary position the upper eyelid margin lies at the superior corneal limbus in children and 1.5–2?mm below it in adults. The lower eyelid margin rests at the inferior corneal limbus.

The margin is covered by cutaneous epithelium through which the eyelashes emerge anteriorly; posteriorly it is interrupted by meibomian gland orifices. The cutaneous epithelium is continuous with the conjunctival epithelium at the posterior border of the lid margin.

Orbicularis Muscle

The orbicularis oculi is a complex striated muscle sheet that lies just below the skin. It is divided anatomically into three contiguous parts ( Fig. 82-1 ): orbital, preseptal, and pretarsal.

The orbital portion overlies the bony orbital rims. It arises from insertions on the frontal process of the maxillary bone, the orbital process of the frontal bone, and the common medial canthal tendon. Its fibers pass around the orbital rim to form a continuous ellipse without interruption at the lateral palpebral commissure.

The palpebral portion of the orbicularis muscle overlies the mobile eyelid from the orbital rims to the eyelid margins. The muscle fibers sweep circumferentially around each eyelid as a

 

 

Figure 82-1 Orbicularis and frontalis muscles. (Adapted from Dutton JJ: Atlas of clinical and surgical orbital anatomy. Philadelphia: WB Saunders; 1994.)

half ellipse, fixed medially and laterally at the canthal tendons. It is further divided topographically into two parts, the preseptal and pretarsal orbicularis.

The preseptal portion of the muscle is positioned over the orbital septum in both upper and lower eyelids, and its fibers originate perpendicularly along the upper and lower borders of the medial canthal tendon. Fibers arc around the eyelids and insert along the lateral horizontal raphe. The pretarsal portion of the muscle overlies the tarsal plates. Its fibers originate from the medial canthal tendon via separate superficial and deep heads, arc around the lids, and insert onto the lateral canthal tendon and raphe. Contraction of these fibers aids in the lacrimal pump mechanism.[2] Medially, the deep heads of the pretarsal fibers fuse to form a prominent bundle of fibers, Horner’s muscle, that runs just behind the posterior limb of the canthal tendon. It inserts onto the posterior lacrimal crest. Horner’s muscle helps maintain the posterior position of the canthal angle, tightens the eyelids against the globe during eyelid closure, and may aid in the lacrimal pump mechanism. [3]

Orbital Septum

The orbital septum is a thin, fibrous, multilayered membrane that begins anatomically at the arcus marginalis along the orbital

 

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Figure 82-2 Orbital septum. (Adapted from Dutton JJ: Atlas of clinical and surgical orbital anatomy. Philadelphia: WB Saunders; 1994.)

rim; it represents a continuation of the orbital fascial system. Distal fibers of the orbital septum merge into the anterior surface of the levator aponeurosis ( Fig. 82-2 ).[4] [5] The point of insertion usually is about 3–5?mm above the tarsal plate, but it may be as much as 10–15?mm above it.[6] In the lower eyelid the septum fuses with the capsulopalpebral fascia several millimeters below the tarsus, and the common fascial sheet inserts onto the inferior tarsal edge. [7] [8]

Preaponeurotic Fat Pockets

The preaponeurotic fat pockets in the upper eyelid and the precapsulopalpebral fat pockets in the lower eyelid are anterior extensions of extraconal orbital fat. These eyelid fat pockets are surgically important landmarks and help identify a plane immediately behind the orbital septum and anterior to the major eyelid retractors. In the upper eyelid, two fat pockets typically occur—a medial pocket and a central one. Laterally, the lacrimal gland may be mistaken for a third fat pocket. In the lower eyelid, three pockets occur—medial, central, and lateral.

Major Eyelid Retractors

The retractors of the upper eyelid consist of the levator palpebrae and Müller’s muscles. The levator palpebrae superioris arises from the lesser sphenoid wing and runs forward just above the superior rectus muscle. Near the superior orbital rim, a condensation is seen along the muscle sheath,[9] which attaches medially and laterally to the orbital walls and soft tissues. This is the superior transverse orbital ligament of Whitnall. It appears to provide some support for the fascial system that maintains spatial relationships between a variety of anatomical structures in the superior orbit.

From Whitnall’s ligament the muscle passes into its aponeurosis ( Fig. 82-3 ). This sheet continues downward 14–20?mm to its insertion near the marginal tarsal border. The aponeurotic fibers are most firmly attached at about 3–4?mm above the eyelid margin.[10] [11] Beginning near the upper edge of the tarsus, the aponeurosis also sends numerous delicate interconnecting slips forward and downward to insert onto the interfascicular septa of the pretarsal orbicularis muscle and subcutaneous tissue. These

 

 

Figure 82-3 Levator aponeurosis and medial and lateral canthal tendons. (Adapted from Dutton JJ: Atlas of clinical and surgical orbital anatomy. Philadelphia: WB Saunders; 1994.)

multilayered slips maintain the close approximation of the skin, muscle, aponeurosis, and tarsal lamellae, and thus integrate the distal eyelid as a single functional unit. This relationship defines the upper eyelid crease of the Caucasian and black eyelid. In the Asian eyelid the crease is lower and less well defined.

As the levator aponeurosis passes into the eyelid from Whitnall’s ligament, it broadens to form the medial and lateral “horns.” The lateral horn forms a prominent fibrous sheet that indents the posterior aspect of the lacrimal gland, and so defines its orbital and palpebral lobes. The medial horn is not as well developed. It blends with the intermediate layer of the orbital septum and inserts onto the posterior crus of the medial canthal tendon and the posterior lacrimal crest. Together, the two horns serve to distribute the forces of the levator muscle along the aponeurosis and the tarsal plate.

In the lower eyelid, the capsulopalpebral fascia is a fibrous sheet that arises from Lockwood’s ligament and the sheaths around the inferior rectus and inferior oblique muscles. It passes upward and generally fuses with fibers of the orbital septum about 4–5?mm below the tarsal plate. From this junction, a common fascial sheet continues upward and inserts onto the lower border of the tarsus.

Sympathetic Accessory Retractors

Smooth muscles innervated by the sympathetic nervous system are present in both the upper and lower eyelids and serve as accessory retractors.[12] In the upper eyelid, the supratarsal muscle of Müller originates abruptly from the undersurface of the levator muscle just anterior to Whitnall’s ligament. [13] It runs downward, posterior to the levator aponeurosis, to which it is adherent, and inserts onto the anterior edge of the superior tarsal border. In the lower eyelid, the sympathetic muscle is not as well defined. Fibers run behind the capsulopalpebral fascia to insert 2–5?mm below the tarsus.[14]

Disruption of sympathetic innervation to these muscles results in Horner’s syndrome. This is characterized by the classic triad of ptosis, miosis, and ipsilateral anhidrosis of the face. Specific clinical findings vary according to the location of the lesion along the polysynaptic pathway.

 

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Tarsal Plates

The tarsal plates consist of dense, fibrous tissue 1–1.5?mm thick that imparts structural integrity to the eyelids. Each plate measures about 25?mm horizontally and is curved gently to conform to the contour of the anterior globe; the central height of the tarsal plates is 8–12?mm in the upper eyelid and 3.5–4?mm in the lower. Medially and laterally they taper to 2?mm in height as they pass into the canthal tendons. Within each tarsus are the meibomian glands, numbering about 25 in the upper lid and 20 in the lower lid. These are holocrine-secreting sebaceous glands that are not associated with lash follicles. They produce the lipid layer of the precorneal tear film.

Canthal Tendons

Medially, the tarsal plates pass into fibrous bands that form the crura of the medial canthal tendon. These lie between the orbicularis muscle anteriorly and the conjunctiva posteriorly. The superior and inferior crura fuse to form a stout common tendon that inserts via three limbs (see Fig. 82-3 ).[2] The anterior limb inserts onto the orbital process of the maxillary bone in front of and above the anterior lacrimal crest. It provides the major support for the medial canthal angle. The posterior limb arises from the common tendon near the junction of the superior and inferior crura and passes between the canaliculi. It inserts onto the posterior lacrimal crest just in front of Horner’s muscle. The posterior limb directs the vector forces of the canthal angle backward to maintain close approximation with the globe. The superior limb of the medial canthal tendon arises as a broad arc of fibers from both the anterior and posterior limbs. It passes upward to insert onto the orbital process of the frontal bone. The posterior head of the preseptal orbicularis muscle inserts onto this limb, and the unit forms the soft tissue roof of the lacrimal sac fossa. This tendinous extension may provide vertical support to the canthal angle,[15] but it also appears to play a significant role in the lacrimal pump mechanism.

Laterally, the tarsal plates pass into not very well developed fibrous strands that become the crura of the lateral canthal tendon. The lateral canthal tendon is a distinct entity separate from the orbicularis muscle; it measures about 1?mm in thickness, 3?mm in width, and approximately 5–7?mm in length.[16] The insertion of these fibrous strands extends posteriorly along the lateral orbital wall, where it blends with strands of the lateral check ligament from the sheath of the lateral rectus muscle.

Conjunctiva

The conjunctiva is a mucous membrane that covers the posterior surface of the eyelids and the anterior pericorneal surface of the globe. The palpebral portion is applied closely to the posterior surface of the tarsal plate and the sympathetic tarsal muscle of Müller. It is continuous around the fornices above and below, where it joins the bulbar conjunctiva. Small accessory lacrimal glands are located within the submucosal connective tissue.

A small mound of tissue, the caruncle, is at the medial canthal angle. The caruncle consists of modified skin that contains fine hairs, sebaceous glands, and sweat glands. Just lateral to the caruncle is a vertical fold of conjunctiva, the plica semilunaris.

NERVES TO THE EYELIDS

The motor nerves to the orbicularis oculi muscle derive from the facial nerve (seventh cranial nerve) through its temporal and zygomatic branches ( Fig. 82-4 ). The facial nerve separates into two divisions, the upper temporofacial and the lower cervicofacial. [17] The upper division further subdivides into the temporal and zygomatic branches, which innervate the frontalis and orbicularis muscles, respectively. The lower cervicofacial division gives rise to the buccal, mandibular, and cervical branches, which innervate muscles of the lower face and neck.

 

 

Figure 82-4 Motor nerve supply to the eyelids; the facial nerve. (Adapted from Dutton JJ: Atlas of clinical and surgical orbital anatomy. Philadelphia: WB Saunders; 1994.)

 

 

Figure 82-5 Sensory nerve supply from the eyelids. (Adapted from Dutton JJ: Atlas of clinical and surgical orbital anatomy. Philadelphia: WB Saunders; 1994.)

The sensory nerves to the eyelids derive from the ophthalmic and maxillary divisions of the trigeminal nerve ( Fig. 82-5 ). Sensory input from the upper lid passes to the ophthalmic division primarily through its main terminal branches, the supraorbital, supratrochlear, and lacrimal nerves. The infratrochlear nerve receives sensory information from the extreme medial portion of both upper and lower eyelids. The zygomaticotemporal branch of the maxillary nerve innervates the lateral portion of the upper eyelid and temple. These branches also innervate portions of the adjacent brow, forehead, and nasal bridge.

 

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Figure 82-6 Arterial supply to and venous drainage from the eyelids. (Adapted from Dutton JJ: Atlas of clinical and surgical orbital anatomy. Philadelphia: WB Saunders; 1994.)

The lower eyelid sends sensory impulses to the maxillary division via the infraorbital nerve. The zygomaticofacial branch from the maxillary nerve innervates the lateral portion of the lower lid, and part of the infratrochlear branch receives input from the medial lower lid.

VASCULAR SUPPLY TO THE EYELIDS

Vascular supply to the eyelids is extensive. The posterior eyelid lamellae receive blood through the vascular arcades. In the upper eyelid, a marginal arcade runs about 2?mm from the eyelid margin, and a peripheral arcade extends along the upper border of the tarsus between the levator aponeurosis and Müller’s muscle ( Fig. 82-6 ). These arcades are supplied medially by the superior medial palpebral vessel from the terminal ophthalmic artery and laterally by the superior lateral palpebral vessel from the lacrimal artery. The lower lid arcade receives blood from the medial and lateral inferior palpebral vessels.

The venous drainage system is not as well defined as the arterial system. Drainage is mainly into several large vessels of the facial system (see Fig. 82-6 ). Lymphatic drainage from the eyelids is restricted to the region anterior to the orbital septum. Drainage from the lateral two thirds of the upper eyelid and the lateral one third of the lower eyelid proceeds inferiorly and laterally into the deep and superficial parotid and submandibular nodes. Drainage from the medial one third of the upper eyelid and the medial two thirds of the lower eyelid occurs medially and inferiorly into the anterior cervical nodes.

 

 

REFERENCES

 

1. Hrecko T, Farkas LG, Katic M. Clinical significance of age-related changes in the palpebral fissure between ages 2 and 18 in healthy Caucasians. Acta Chir Plast. 1968;32:194–204.

 

2. Dutton JJ. Atlas of clinical and surgical orbital anatomy. Philadelphia: WB Saunders; 1994.

 

3. Ahl NC, Hill JC. Horner’s muscle and the lacrimal system. Arch Ophthalmol. 1982;100:488–93.

 

4. Barker DE. Dye injection studies of orbital fat compartments. Plast Reconstr Surg. 1977;59:82–5.

 

5. Putterman AM, Urist MJ. Surgical anatomy of the orbital septum. Ann Ophthalmol. 1974;6:290–4.

 

6. Anderson RL, Dixon RS. The role of Whitnall’s ligament in ptosis surgery. Arch Ophthalmol. 1979;97:705–10.

 

7. Harvey JT, Anderson RL. The aponeurotic approach to eyelid retraction. Ophthalmology. 1981;88:513–24.

 

8. Meyer DR, Linberg JV, Wobig JL, McCormick S. Anatomy of the orbital septum and associated eyelid connective tissue. Ophthal Plast Reconstr Surg. 1991;7:104–13.

 

9. Lemke BN, Stasior OG, Rosenberg PN. The surgical relations of the levator palpebrae superioris muscle. Ophthal Plast Reconstr Surg. 1988;4:25–30.

 

10. Anderson RL, Beard C. The levator aponeurosis. Attachments and their clinical significance. Arch Ophthalmol. 1977;95:1437–41.

 

11. Collin JRO, Beard C, Wood I. Experimental and clinical data on the insertion of the levator palpebrae superioris muscle. Am J Ophthalmol. 1987;85:792–801.

 

12. Manson PN, Lazarus RB, Magar R, Iliff N. Pathways of sympathetic innervation to the superior and inferior (Müller’s) tarsal muscles. Plast Reconstr Surg. 1986;78:33–40.

 

13. Kuwabara T, Cogan DG, Johnson CC. Structure of the muscles of the upper eyelid. Arch Ophthalmol. 1975;93:1189–97.

 

14. Hawes MJ, Dortzbach RK. The microscopic anatomy of the lower eyelid retractors. Arch Ophthalmol. 1982;100:1313–8.

 

15. Anderson RL. The medial canthal tendon branches out. Arch Ophthalmol. 1977;95:2951–61.

 

16. Gioia VM, Linberg JV, McCormick SA. The anatomy of the lateral canthal tendon. Arch Ophthalmol. 1987;105:529–32.

 

17. Malone B, Maisel RH. Anatomy of the facial nerve. Am J Otolaryngol. 1988;9:494–504.

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