Understanding eyelid anatomy is essential not only for examinations but also for clinical decision-making.
However, simply memorizing structures is not enough. A far more effective approach is to repeatedly draw the anatomy yourself from scratch—this helps transform knowledge into long-term retention.

Basic Structure of the Upper Eyelid

Orbital Septum: The Key Landmark

The orbital septum is a thin fibrous membrane extending from the orbital rim to the tarsal plate.

This structure divides the upper eyelid into two layers:

  • Anterior lamella
  • Posterior lamella

Anterior Lamella

Contains:

  • Orbicularis oculi muscle
  • Glands of Moll
  • Glands of Zeis

Posterior Lamella

Contains:

  • Tarsal plate
  • Levator palpebrae superioris muscle
  • Müller’s muscle
  • Conjunctiva

Clinical Importance of the Orbital Septum

The orbital septum plays a critical role as a barrier against the spread of infection and hemorrhage.

This distinction is essential in eyelid infections:

Preseptal cellulitis (anterior to the septum)

Usually managed with oral antibiotics on an outpatient basis

Orbital cellulitis (posterior to the septum)

Requires hospitalization and intravenous antibiotics.
Risk of serious complications such as intracranial spread (e.g., meningitis).

In practice, identifying whether inflammation crosses the orbital septum directly impacts management strategy.

Meibomian Glands

The Meibomian glands are specialized sebaceous glands located within the tarsal plate.

Secrete meibum, composed mainly of:

  • Wax esters
  • Cholesterol esters

More numerous in the upper eyelid than the lower eyelid.

Clinical relevance:

Dysfunction leads to:

  • Internal hordeolum
  • Chalazion

Glands of Zeis and Moll

Glands of Zeis

  • Sebaceous glands located at the eyelash follicles
  • Infection → External hordeolum (stye)

Glands of Moll

  • Apocrine sweat glands at the eyelash follicles
  • Infection → External hordeolum (stye)

    Both glands are involved in anterior eyelid infections, but their histological origin differs.

    Accessory Lacrimal Glands

      There are two types of accessory lacrimal glands: Krause Glands, Wolfring Glands.

      These glands contribute to basal tear secretion, complementing the main lacrimal gland.

      Krause Glands

      Open into the conjunctival fornix

      Wolfring Glands

      Open near the upper border of the tarsal plate

      Müller’s Muscle and Sympathetic Control

        The Müller’s muscle is a smooth muscle innervated by the sympathetic nervous system.

        Clinical correlations:

        In Horner syndrome

        • Sympathetic dysfunction
        • Relaxation of Müller’s muscle
        • Mild ptosis

        In Graves disease

        • Increased sympathetic activity
        • Overcontraction of Müller’s muscle
        • Eyelid retraction

        Summary

        The orbital septum is the most important anatomical landmark in eyelid infections.

        Eyelid glands are divided into:

        • Meibomian (tarsal, lipid secretion)
        • Zeis (sebaceous, eyelash-associated)
        • Moll (apocrine, eyelash-associated)

        Accessory lacrimal glands contribute to tear production
        Müller’s muscle links eyelid position to autonomic function