Anatomy

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Anatomy

A thorough understanding of the anatomy of the eye, orbit, visual pathways, upper cranial nerves, and central pathways for the control of eye movements is a prerequisite for proper interpretation of diseases having ocular manifestations. Furthermore, such anatomic knowledge is essential to the proper planning and safe execution of ocular and orbital surgery.

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The Ocular Adnexa

Eyebrows

Eyelids

Lacrimal Apparatus

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Eyelids

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From superficial to deep, they are the skin layer, a layer of striated muscle (orbicularis oculi), areolar tissue, fibrous tissue (tarsal plates), and a layer of mucous membrane (palpebral conjunctiva)

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Lid Margins

Anterior Margin

Eyelashes

Glands of Zeis

Glands of Moll

Posterior Margin

small orifices of modified sebaceous glands (meibomian, or tarsal, glands).

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Orbital Septum

the fascia behind that portion of the orbicularis muscle that lies between the orbital rim and the tarsus and serves as a barrier between the lid and the orbit.

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Lid Retractors

The lid retractors are responsible for opening the eyelids.

In the upper lid: levator palpebrae superioris & Muller's (superior tarsal) muscle

In the lower lid:the main retractor is the inferior rectus

The smooth muscle components of the lid retractors are innervated by sympathetic nerves.

The levator and inferior rectus muscles are supplied by the third cranial (oculomotor) nerve. Ptosis is thus a feature of both Horner's syndrome and third nerve palsy

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Sensory Nerve Supply

first and second divisions of the trigeminal nerve (V).

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Blood Supply & Lymphatics

the lacrimal and ophthalmic arteries by their lateral and medial palpebral branches.

Venous drainage from the lids empties into the ophthalmic vein and the veins that drain the forehead and temple