CHAPTER 19

EYE AND ORBIT

Overview and Topographic Anatomy of the Orbit

Osteology of the Orbit

Contents of the Orbit

Clinical Correlates

Questions

Overview and Topographic Anatomy of the Orbit

GENERAL INFORMATION

Orbit: a pyramid-shaped bony recess in the anterior part of the skull, lined by periosteum called the periorbital fascia

Contents include:

• Eye—organ associated with vision

• Extrinsic muscles

• Optic nerve

• Oculomotor nerve

• Ciliary ganglion

• Trochlear nerve

• Ophthalmic division of the trigeminal nerve

• Abducens nerve

• Ophthalmic artery and branches

• Superior and inferior ophthalmic veins

• Lacrimal apparatus

• Much fatty tissue

Osteology of the Orbit

OPENINGS IN THE ORBIT

BONES CREATING THE ORBITAL MARGIN

WALLS OF THE ORBIT

Contents of the Orbit

EYE

Eye: a spherical globe with a diameter of approximately 2.5 cm that lies in the orbit’s anterior portion

Surrounded by a thin capsule called the fascia bulbi (Tenon’s capsule):

• Provides support

• Allows for movement

Composed of 3 coats:

• Sclera

• Uveal tract

• Retina

Divided into an anterior and a posterior segment:

Anterior Segment:

• Filled with aqueous humor

• Separated into anterior and posterior chambers by the iris

• Contains aqueous humor secreted by the ciliary body and drained through a trabeculated network eventually into the superior ophthalmic vein

• Intraocular pressure is measured in the anterior segment, normally 10 to 20 mm Hg

Posterior Segment:

• Filled with vitreous fluid

• Called the vitreous cavity

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