Eyelid Anatomy — Ophthalmology Review (2023)

Eyelid Anatomy — Ophthalmology Review (1)

Palpebral Fissure

  • The palpebral fissure refers to the normal exposed area between upper and lower eyelids.

  • The palpebral fissure vertical height (PFH) is measured between the margin of the lower eyelid to the margin of the upper eyelid.

  • The normal palpebral fissure height is 8-11 mm. This is a key measurement that you need when assessing for ptosis.

Margin-To-Reflex Distance

  • As you might expect, it is the distance from the eyelid margin to the corneal light reflex.

  • It is measured by having the patient fixate on a light, and measuring the distance from the margin of the eyelid to the corneal light reflex. There are two margin-to-reflex distances (MRD), corresponding to the measurement from the upper and lower eyelids:

    • MRD1: upper eyelid margin-to-light reflex; this is probably the single most important measurement when evaluating ptosis.

    • MRD2: lower eyelid margin-to-light reflex

  • MRD1 + MRD2 should equal the palpebral fissure height.

Levator Palpebrae Superioris Function (Excursion)

Eyelid Anatomy — Ophthalmology Review (2)

  • The levator palpebrae superioris muscle is innervated by the superior division of CN III.

  • It is the greatest contributor to upper eyelid movement.

  • It provides 15 mm of eyelid elevation; this can typically be measured by having the patient look down, then as high as possible while holding the frontalis muscle down. Frontalis muscle contracture can open the eyelids an additional 2 mm.

Eyelid Anatomy — Ophthalmology Review (3)

There are several ways to mentally organize the multiple layers of the upper eyelid. The Fundamentals BCSC book lists 9 structures, while the Oculoplastics BCSC book lists 7 structures; they are essentially the same lists so there’s no need to fret over which list to memorize.

I personally have found that thinking through the layers of the eyelid from anterior (external) to posterior (internal) makes the most sense to me. After all, if you are doing eyelid surgery, you are going to make an incision through various layers of the eyelid and it’s helpful to know what tissues you’re cutting through and in what order. The layers are:

  • Skin

  • Subcutaneous connective tissue (the Oculoplastics BCSC book lumps the skin and subcutaneous tissue into one layer, as clinically they are fairly indistinct)

  • Orbicularis oculi muscle

  • Orbital septum

  • Levator palpebrae superioris muscle (not present in the lower eyelid)

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  • Müller muscle (inferior tarsal muscle in the lower eyelid)

  • Tarsus

  • Conjunctiva

The eyelid margin is another unique aspect of the eyelids, which is important to understand for surgical landmarks and various pathologies. This will be discussed in a separate section.

Anterior and Posterior Lamellae

Another method of thinking about eyelids (especially in surgery) is dividing the eyelid into anterior and posterior lamellae. In this framework, the orbital septum separates the anterior tissues from the posterior tissues. When considering certain treatments for conditions such as ectropion or entropion, this may potentially help understand why and how to repair the eyelid tissues.

Anterior Lamellae

  • Skin and connective tissues

  • Orbicularis oculi muscle

Posterior Lamellae

  • Tarsus

  • Conjunctiva


  • The eyelid skin is the thinnest in the body.

  • The skin contains fine hairs, sebaceous glands, and sweat glands.

Eyelid Folds

  • In non-Asians, the levator palpebrae superioris muscle has some attachments to the upper border of the tarsus, which forms a superior eyelid fold.

  • In Asians, the levator palpebrae superioris muscle does not have these attachments, so the superior eyelid fold is minimal or absent.

Subcutaneous Connective Tissue

  • The significant eyelid swelling seen in conditions such as preseptal cellulitis (shown above) is caused by the accumulation of fluid in the loose connective tissue.

Eyelid Anatomy — Ophthalmology Review (5)

Eyelid Anatomy — Ophthalmology Review (6)

Orbicularis Oculi Muscle

The orbicularis muscle consists of the concentric bands of muscle surrounding the eyelid. It is innervated by the facial nerve (CN VII). It has multiple functions, including involuntary blinking, voluntarily and forcibly closing the eyelids, and tear drainage.

Eyelid Anatomy — Ophthalmology Review (7)

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Eyelid Anatomy — Ophthalmology Review (8)


There are 2 sections of the orbicularis oculi muscle:

  • Orbital segment

  • Palpebral segment: further subdivided into the pretarsal and preseptal segments

    • Pretarsal segment

    • Preseptal segment

Orbital Segment of the Orbicularis Oculi Muscle

  • The orbital segment provides voluntary forced closure of the eyelids.

Pretarsal segment of the Orbicularis Oculi Muscle

  • The pretarsal segment is involved in tear drainage (“preTarsal helps with Tearing”)

  • The portion that attaches to the anterior and posterior lacrimal crest is called the Horner muscle.

  • The upper and lower eyelid segments fuse laterally to form the lateral canthal tendon.

Preseptal segment of the Orbicularis Oculi Muscle

  • The preseptal muscles form the lateral palpebral ligament (raphe), which inserts into Whitnall’s tubercle.

Riolan Muscle

  • The muscle of Riolan represents the most superficial portion of the orbicularis muscle.

  • It corresponds to the gray line of the eyelid margin, and may contribute to meibomian gland secretion, eyelash position, and blinking.

  • It arises from the palpebral segment of the orbicularis muscle.

Orbital Septum

  • The orbital septum is an extension of periosteum from the orbital roof (upper eyelid) and orbital floor (lower eyelid).

  • It serves as a barrier for preventing infections/blood/inflammation from spilling over between the anterior eyelid and the orbit.

    • Preseptal cellulitis refers to inflammation and infections that are anterior (superficial) to the orbital septum. These may be treated with oral or IV antibiotics first, and may not require additional hospital treatment or surgery.

    • Orbital celluiltis affects the tissues posterior to the orbital septum and may result in subperiosteal abscesses, cavernous sinus thrombosis, or systemic infection.

  • It separates the anterior lamellae of the eyelid from the posterior lamellae.

Levator Palpebrae Superioris Muscle

Eyelid Anatomy — Ophthalmology Review (9)

  • The levator palpebrae superioris muscle travels from the posterior orbit (arising from the lesser wing of the sphenoid).

  • It is innervated by the superior division of CN III. There one common central subnuclei for the eyelids present in the CN III nucleus.

    • Lesions in the midbrain affecting the CN III nucleus on one side may result in an ipsilateral CN III palsy with bilateral ptosis.

    • In accordance with Hering’s law of equal innervation, unilateral ptosis may create the false impression of contralateral eyelid retraction; likewise, unilateral eyelid retraction may result in contralateral pseudoptosis.

  • The Whitnall ligament (a condensation of the superior rectus and levator palpebrae superioris muscles) affects the levator palpebrae superioris muscle in several ways:

    • At the Whitnall ligament, the levator palpebrae superioris muscle changes direction from horizontal to vertical.

    • At the Whitnall ligament, the levator palpebrae superioris muscle divides into the levator aponeurosis and the superior tarsal (Müller) muscle.

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Superior Tarsal (Müller) Muscle

The superior tarsal muscle, also termed the Müller muscle, is a smooth muscle (nonstriated, as opposed to the striated/skeletal muscles of the orbicularis oculi, levator palpebrae superioris, and other extraocular muscles). It is innervated by the sympathetic nerves with cell bodies in the superior cervical ganglion. It provides a small amount of additional eyelid retraction.

  • Müller muscle originates from the posterior surface of the levator palpebrae superioris muscle at the level of the Whitnall ligament and inserts on the upper border of the tarsus. There are also attachments to the conjunctiva at the upper fornix.

  • There is a sympathetically-innervated muscle in the lower eyelid that functions as the analogue of the Müller muscle, the capsulopalpebral (inferior tarsal) muscle, which inserts on the lower border of the lower eyelid tarsus.

  • In Horner syndrome, loss of sympathetic tone results in ~2 mm of upper eyelid ptosis and also lower lid ptosis.

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  • The tarsal plates of the eyelids are comprised of dense connective tissue.

  • They are attached to the periosteum horizontally via the medial and lateral canthal tendons.

  • The meibomian glands of the eyelid are holocrine sebaceous glands that lie within the tarsus. They produce oil which forms the oily layer of the tear film.

    • There are more meibomian orifices in the upper eyelid compared to the lower eyelid (30-40 vs. 20-30).

  • The upper tarsus is wider than the lower tarsus.

  • With age the medial and lateral canthal tendons stretch and become more lax, resulting in horizontal displacement of the tarsal plate. A lateral tarsal strip procedure sutures the lateral tarsus to the periosteum, restoring the horizontal tension on the tarsus.

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The conjunctiva is a transparent vascularized membrane that covers the eyelids (palpebral conjunctiva) and globe (bulbar conjunctiva).

  • It is composed of nonkeratinizing squamous epithelium.

  • It contains goblet cells, which secrete mucin (forming the mucin layer of the tear film).

  • It contains accessory lacrimal glands of Wolfring and Krause, which secrete the basal aqueous layer of the tear film.

    • The glands of Wolfring are located along the upper border of the tarsus in the upper lid and the lower border of the tarsus in the lower lid (“nonmarginal tarsal borders”).

    • The glands of Krause are located in the fornices (“Krause in the crack”).

The eyelid margin contain many important structures and are ordered in specific way, as are all the layers of the eyelid. Knowing the orientation and position of the margin structures is especially important with trauma, where restoration of the anatomy as best as possible is critical.

From anterior to posterior, the structures seen are:

  • Skin

  • Eyelashes (cilia)

  • Gray line

  • Meibomian gland orifices

  • Mucocutaneous junction

  • Palpebral conjunctiva

Eyelid Anatomy — Ophthalmology Review (12)

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Special Structures Of the Eyelid Margin


The puncta of the canaliculus is present at the medial aspect of each eyelid margin.

  • The upper (superior) punctum is more medially located than the lower (inferior) punctum.

Gray Line (Intermarginal sulcus)

  • The gray line of the eyelid margin represents the most superficial portion of the palpebral (pretarsal) orbicularis oculi muscle, the muscle of Riolan.

Eyelashes (Cilia)

Eyelashes arise from the anterior eyelid margin just anterior to the tarsal plate.

  • Glands of Zeis are modified sebaceous glands associated with the cilia (“Zei-baceous” glands)

  • Glands of Moll are apocrine sweat glands in the skin.

Arterial Supply

The eyelids are supplied by both the external carotid artery and internal carotid artery systems.

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External Carotid Artery System

  • The facial artery from the ECA (facial system) becomes the angular artery lateral to the nose and supplies the medial eyelid.

    • The angular artery is an important surgical landmark in dacryocystorhinostomy (DCR).

  • The temporal artery from the ECA supplies the lateral eyelid.

Internal Carotid Artery System

  • The circulation from the internal carotid artery (orbital system) arises from branches of the ophthalmic artery, namely the supraorbital and lacrimal arteries.

Arterial Arcades

  • Marginal arterial arcade: located 2-3 mm from the eyelid margin, it lies just above the ciliary follicles, either within the tarsus or between the tarsal plate and orbicularis oculi muscle.

  • Peripheral arterial arcade: located within the Müller/inferior tarsal muscles, at the border of the tarsus and those muscles.

Venous Drainage

Superficial (Pretarsal) System

  • These veins drain from preseptal tissues into the internal and external jugular veins.

    • The angular vein supplies the medial eyelid.

    • The superficial temporal vein supplies the lateral eyelid.

Deep (Posttarsal) System

  • These veins drain into the cavernous sinus.

    • Some notable veins include the orbital veins and deep branches of the anterior facial vein and pterygoid plexus.

Medial Drainage

  • The lymphatic vessels that serve the medial eyelids drain into the submandibular lymph nodes (Medial eyelids = subMandibular nodes).

Lateral Drainage

  • The lymphatic vessels that serve the lateral eyelids drain into the preauricular lymph nodes (lateral eyelids go to the ear).

Eyelid Anatomy — Ophthalmology Review (14)


  • The caruncle is modified skin.

  • Histologically it is covered by nonkeratinized, stratified squamous epithelium and contains sebaceous glands and hair.

Plica Semilunaris

  • The plica semilunaris is a fold of the conjunctiva on the medial aspect of the globe.

  • Histologically, it resembles bulbar conjunctiva but the stroma contains fat and some nonstriated muscle. The epithelium is rich with goblet cells.

  • Of note (but probably not of testing consequence), it is a vestigial structure analogous to the nictitating membrane (third eyelid) of other animals.

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  • Basic and Clinical Science Course, Section 2. Fundamentals and Principles of Ophthalmology. San Francisco: American Academy of Ophthalmology, 2018-2019:18-27.

  • Basic and Clinical Science Course, Section 7. Orbit, Eyelids, and Lacrimal System. San Francisco: American Academy of Ophthalmology, 2018-2019:145-154.

  • Tong J, Patel BC. Anatomy, Head and Neck, Eye Orbicularis Oculi Muscle. StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available online from the National Library of Medicine.


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