Eyelid Anatomy

Overview

Each eye is protected by upper and lower eyelids (palpebrae). The eyelids meet at two corners — the medial canthus (near the nose) and the lateral canthus (toward the temple). The free margin of each lid is approximately 30 mm long and carries two to three rows of lashes (cilia).

The upper eyelid normally rests 1–2 mm below the superior limbus of the cornea. The lower lid rests at or just above the inferior limbus. Any deviation from these positions — whether drooping, turning in, or turning out — is a surgical indication that oculoplastic surgeons are trained to correct.

Eyelid Layers

From anterior (front) to posterior (back), the eyelid consists of five layers:

1. 1
   Skin

   The thinnest skin in the body — typically 0.5–1 mm. It contains fine hair follicles and sebaceous glands, and becomes redundant with age, contributing to dermatochalasis (hooded lids).

2. 2
   Orbicularis Oculi

   A circular muscle responsible for eyelid closure. The orbital portion closes forcefully (blink, squint); the preseptal and pretarsal portions perform gentle, reflex blinking. Paralysis of this muscle — as in facial nerve palsy — causes lagophthalmos (inability to close the eye).

3. 3
   Orbital Septum

   A fibrous membrane that acts as the anterior boundary of the orbit, keeping orbital fat behind the eyelid. The septum fuses with the levator aponeurosis in the upper lid and the capsulopalpebral fascia in the lower lid. Septal weakness allows prolapse of orbital fat ("bags under the eyes").

4. 4
   Tarsus (Tarsal Plate)

   A dense fibrous plate that provides structural rigidity to the eyelid. The upper tarsus is roughly 10–12 mm in height; the lower tarsus 3–4 mm. It contains the Meibomian glands, which secrete the lipid layer of the tear film. The tarsus is the key landmark in most eyelid reconstructive procedures.

5. 5
   Conjunctiva

   A transparent mucous membrane lining the posterior surface of the lid and folding forward to cover the anterior sclera. It contains goblet cells that contribute to the mucin layer of the tear film. The palpebral conjunctiva is firmly adherent to the tarsus; the bulbar conjunctiva covers the globe.

Upper Eyelid Anatomy

The upper eyelid is primarily opened (elevated) by two muscles:

Lower Eyelid Anatomy

The lower eyelid lacks a true retractor muscle comparable to the levator. Inferior retraction is provided by the capsulopalpebral fascia — an extension of the inferior rectus muscle sheath that inserts onto the inferior tarsal border. Below the tarsus, the orbital septum contains three fat compartments:

• Medial fat pad — separated from the central compartment by the inferior oblique muscle
• Central fat pad — the most prominent; herniation creates the classic infraorbital "bag"
• Lateral fat pad — smaller, less commonly symptomatic

The lower lid position is primarily maintained by the canthal tendons and orbicularis tone. When these weaken with age, the lid may turn inward (entropion) or outward (ectropion) — two of the most common oculoplastic conditions.

Canthal Tendons

Lacrimal Drainage

Tears are produced by the lacrimal gland (superolateral orbit) and accessory lacrimal glands (conjunctiva). They flow across the ocular surface and drain medially through the lacrimal drainage system:

1. Puncta — two small openings on the medial upper and lower lid margins
2. Canaliculi — small canals leading medially, joining into a common canaliculus
3. Lacrimal sac — a small reservoir in the medial canthal area
4. Nasolacrimal duct — drains inferiorly into the inferior nasal meatus

Obstruction anywhere along this pathway causes epiphora (tearing). The eyelid's "lacrimal pump" — powered by the orbicularis and medial canthal tendon — actively propels tears through the system with each blink.

Fitzpatrick Skin Phototypes

The Fitzpatrick classification divides skin into six phototypes based on response to ultraviolet exposure. For eyelid surgery and skin tumor management, phototype influences healing characteristics, hyperpigmentation risk, keloid tendency, and skin cancer incidence.

Types I–III have the highest risk of UV-induced skin cancer (basal cell carcinoma, squamous cell carcinoma, melanoma). Types IV–VI have lower skin cancer rates but are more prone to post-inflammatory hyperpigmentation and keloid formation following eyelid surgery.

Clinical Relevance

A precise understanding of eyelid anatomy allows Dr. Brown to identify the exact anatomical layer responsible for each patient's condition and to plan surgery that corrects it with the least disruption to surrounding structures.