Anatomy of Eyelids - 7 Layers of Eyelids You Need to Know. - Smart Optometry (2024)

Gross Anatomy of Eyelids:

What is the definition of Eyelids?

  • The eyelids are protective, mobile tissue curtains in front of the eyeballs.
  • They act as shutters to shield the eyes from injuries, light, and help spread the tear film over the eye’s surface.
  • Eyelids play a role in facial expressions and provide cues about a person’s wakefulness and attention.
Anatomy of Eyelids - 7 Layers of Eyelids You Need to Know. - Smart Optometry (1)

Extend of Eyelids (Anatomy of Eyelids):

  • Extent of Upper Eyelid:
    • Extends downward from the eyebrow and forms the top boundary of the eye opening (palpebral fissure).
  • Extent of Lower Eyelid:
    • Extends upward to meet the skin of the cheek, creating the lower boundary of the eye opening.

Folds of Eyelid:

  • Upper Eyelid Fold:
    • Divides the eyelid into an orbital and a tarsal portion, formed by fibers from the levator muscle.
  • Lower Eyelid Fold:
    • Less prominent, marks the boundary between the eyelid and cheek area.
  • Nasojugal and Malar Folds:
    • These folds on the lower eyelid limit the spread of blood or fluid into the cheek.

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Canthi/Canthus of Eyelids:

  • Medial Canthus of Eyelids:
    • The inner angle where eyelids meet, separated from the eyeball by the tear lake (lacus lacrimalis).
  • Lateral Canthus of Eyelids:
    • The outer angle, which lies in contact with the eyeball, forming an angle that changes with the eye’s opening.

Margins of Eyelids:

  • Divided into a Medial Lacrimal Portion (rounded, no lashes, or glands) and a Lateral Ciliary Portion.
  • The Grey Line marks the division between skin and conjunctiva, where lashes and meibomian gland openings are located.

Eyelashes of Eyelids:

  • Arranged in 2-3 rows: Upper lid lashes (100-150) curve upward, lower lid lashes (50-75) curve downward to avoid interlocking when closed.
  • Lashes are dark, fine-tapered, and renew every 3-4 months.

Palpebral Fissure of Eyelids:

  • The elliptical space between the eyelids, which is approximately 28-30 mm horizontally and 9-11 mm vertically in adults.
  • The alignment of the fissure can vary: some have a slight upward tilt (mongoloid slant), while others may tilt slightly downward (antimongoloid slant).

Associated Glands of Eyelids:

Anatomy of Eyelids - 7 Layers of Eyelids You Need to Know. - Smart Optometry (2)

Glands of Zeis:

  • Sebaceous glands that empty into the lash follicles.

Glands of Moll:

  • Apocrine glands also associated with lash follicles, providing lubrication.

Note: These glands and lash follicles are highly sensitive, responding to touch for eye protection.

Anatomy/Structures of Eyelids:

What are the Layers of Eyelids (Structures of Eyelids)?

  • Eyelid has 7 layers:
    • 1. Skin
    • 2. Subcutaneous areolar tissue
    • 3. Striated muscle
    • 4. Submuscular areolar tissue
    • 5. Fibrous layer
    • 6. Non-striated muscle
    • 7. Conjunctiva
Anatomy of Eyelids - 7 Layers of Eyelids You Need to Know. - Smart Optometry (3)

Note: The skin on our eyelids is the thinnest in the entire body

  • You can easily remember those layers by the mnemonic

“Smart Students Study Subjects For New Concepts”

  • Smart = Skin,
  • Students = Subcutaneous areolar tissue,
  • Study = Striated muscle,
  • Subjects = Submuscular areolar tissue,
  • For = Fibrous layer,
  • New = Non-striated muscle, and
  • Concepts = Conjunctiva.

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1. Skin of Eyelids (Structures of Eyelids):

Anatomy of Eyelids - 7 Layers of Eyelids You Need to Know. - Smart Optometry (4)
  • The eyelid skin is the thinnest on the body, very elastic, and allows the eyelids to move quickly.
  • The nasal skin (near the nose) is smoother and oilier than the skin on the outer part of the eyelid.
  • Microscopic Structure: It consists of several layers of cells (epidermis), including a protective outer layer, and a dermis layer that has connective tissue, blood vessels, lymphatics, and nerves.
  • The skin’s pigment can darken with chronic swelling or irritation.

2. Subcutaneous Areolar Tissue layer of Eyelids (Structures of Eyelids):

Anatomy of Eyelids - 7 Layers of Eyelids You Need to Know. - Smart Optometry (5)
  • A layer of loose connective tissue just below the skin with no fat, allowing easy movement of the skin.
  • This layer can swell with fluid or blood, and it’s also helpful for eyelid surgeries.
  • Not present near the lash line or where skin attaches to ligaments at the eyelid edges.

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3. Striated Muscles layer of Eyelids (Structures of Eyelids):

Anatomy of Eyelids - 7 Layers of Eyelids You Need to Know. - Smart Optometry (6)
  • This layer consists of orbicularis muscle which forms an oval sheet across the eyelids. In addition, the upper eyelid also contains levator muscle.

Orbicularis Oculi Muscle:

  • This muscle encircles the eyelid and has two main parts:

Orbital Part of Orbicularis Oculi Muscle:

  • Helps close the eyelid tightly and supports eyebrow movement.

Palpebral Part of Orbicularis Oculi Muscle:

  • Helps in gentle eyelid closure, such as blinking or during sleep.
  • This part is further divided into:

Preseptal and Pretarsal Portions of Orbicularis Oculi Muscle:

  • Important for tear drainage and keeping the lids close to the eye.

Levator Palpebrae Superioris Muscle (LPS):

  • Only in the upper lid, this muscle lifts the upper eyelid.
  • Its tendon, called the aponeurosis, helps form the upper lid fold and connects to various points in the eyelid structure.

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4. Submuscular Areolar Tissue layer of Eyelids (Structures of Eyelids):

Anatomy of Eyelids - 7 Layers of Eyelids You Need to Know. - Smart Optometry (7)
  • A loose tissue layer between the muscles and deeper structures, containing blood vessels and nerves.
  • It splits the eyelid into front and back sections, allowing for easy surgical access.
  • In the upper eyelid, it has two spaces (pretarsal and preseptal), separated by the levator muscle.
  • These spaces allow movement and house blood supply.

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5. Fibrous Layer of Eyelids (Structures of Eyelids):

Anatomy of Eyelids - 7 Layers of Eyelids You Need to Know. - Smart Optometry (8)
  • The fibrous layer forms the structural support of the eyelids and includes:

a. Tarsal Plate:

  • This is the dense, fibrous tissue that gives the eyelid its shape and rigidity.
  • It’s about 29 mm in length, with the upper tarsus being larger than the lower.

Surfaces of Tarsal Plate:

  • The front (anterior) surface is convex and separates from the orbicularis muscle, allowing smooth movement.
  • The back (posterior) surface curves to align with the eye.

Borders of Tarsal Plate:

  • The edges provide attachment points for key structures like the orbital septum and muscles.

b. Septum Orbitale (Palpebral Fascia):

  • A thin membrane that moves with the eyelids, linking the tarsal plates with the orbital rim.

Attachments and Relations of Septum Orbitale:

  • Attaches to the tarsal plate centrally and to the orbital bone peripherally, allowing it to act as a barrier for orbital fat and connect with the surrounding muscle structures.

c. Medial and Lateral Palpebral Ligaments:

Medial Ligament:

  • Attaches to the frontal bone, providing support and anchoring the eyelids at the inner corner of the eye.

Lateral Ligament:

  • Anchors to the outer corner, connecting the tarsal plates with the orbital margin, ensuring stability during movement.

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6. Non-Striated Muscle Fibers layer of Eyelids (Structures of Eyelids):

Anatomy of Eyelids - 7 Layers of Eyelids You Need to Know. - Smart Optometry (9)
  • This layer consists of Müller’s muscles (smooth muscle fibers), which are controlled by the sympathetic nervous system:

Location and Function of Non-Striated Muscle Fibers layer of Eyelids:

  • Found in both upper and lower eyelids, just beneath the septum orbitale.
  • They help elevate the upper eyelid and slightly lower the lower eyelid.

Sympathetic Control of Non-Striated Muscle Fibers layer of Eyelids:

  • Stimulates lid retraction (pulls eyelids up).
  • If damaged, it can lead to conditions like Horner’s syndrome, where the lid droops due to reduced muscle tone.

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7. Conjunctiva of Eyelids (Structures of Eyelids):

Anatomy of Eyelids - 7 Layers of Eyelids You Need to Know. - Smart Optometry (10)
  • The conjunctiva is the innermost layer of the eyelid:

Structure and Location Conjunctiva of Eyelids:

  • A thin mucous membrane that extends from the inner lid margin to the conjunctival fornix, covering the back of the tarsal plate and Müller’s muscle.

Function Conjunctiva of Eyelids:

  • Provides a protective barrier and helps produce mucus to keep the eye moist.
  • Check Our Courses: Ophthalmic Instrumentation, Clinical Refraction, Contact Lens, Binocular Vision, Dispensing Optics, MCQs in Optometry
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Anatomy of Eyelids - 7 Layers of Eyelids You Need to Know. - Smart Optometry (2024)

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