Oculomotor n.

Trochlear n.

Abducens n.

Ophthalmic n. (V1)

Maxillary n. (V2)

Sphenoid

bone

ANTERIOR CILIARY VEINS

The anterior ciliary veins receive branches from the conjunctival capillary network and then accompany the anterior ciliary arteries, pierce the sclera, and join with the muscular veins.

INFRAORBITAL VEIN

The infraorbital vein is formed by several veins that drain the face. It enters the infraorbital foramen and, along with the infraorbital artery and nerve, passes posteriorly through the infraorbital canal and groove. It receives branches from some structures in the inferior part of the orbit and may communicate with the inferior ophthalmic vein. The infraorbital vein drains into the pterygoid venous plexus (see Figure 11-11).

CAVERNOUS SINUS

The cavernous sinus is a relatively large venous channel formed by a splitting of the dura mater on each side of the body of the sphenoid bone. The cavernous sinus extends from the medial end of the superior orbital fissure to the petrous portion of the temporal bone. The internal carotid artery and the abducens nerve are located medially within the sinus, covered by the endothelial lining of the sinus. The oculomotor, ophthalmic, and maxillary nerves are found in the lateral wall of the cavernous sinus (Figure 11-12).

Clinical Comment:

Carotid­ -­Cavernous Sinus Fistula

A CAROTID-CAVERNOUS SINUS FISTULA  is an abnormal communication between the internal carotid artery and the cavernous sinus caused by a tear in the artery wall, either traumatic or spontaneous. The sinus communicates directly with the veins of the orbit, so arterial pressure can be transmitted to the ophthalmic veins,

which may become pulsatile. If arterial pressure is reduced because of this leak, a decrease in perfusion to ocular tissue will occur.36,37

FIGURE 11-13

Superior view of venous sinus drainage of ­cranium. (From Mathers LH, Chase RA, Dolph J, et al: Clinical anatomy principles, St Louis, 1996, Mosby.)

Parotoid lymph node

Submandibular lymph node

FIGURE 11-14

Lymphatic drainage of the ocular adnexa. medial lids and conjunctiva drain into submandibular lymph node, lateral lids conjunctiva drain into parotoid lymph node.

L Y M P H A T I C D R A I N A G E

No lymphatic vessels occur in the globe proper; lymphatics are found in the conjunctiva and the eyelids. The lymphatics that drain the medial aspects of the lids and the medial canthal structures (including the lacrimal sac) empty into the submandibular lymph nodes. Those that drain the lateral eyelids and the lacrimal gland empty into the parotid lymph nodes in the preauricular area9,35 (Figure 11-14).

E F F E C T O F A G I N G O N O C U L A R C I R C U L A T I O N

Changes occurring with age differ between individuals. Genetic and environmental factors are contributory, but there are some generalities that can be made. The density of the choroidal and retinal capillary beds and choroidal and retinal vessel diameter all decrease with age.38 Endothelial dysfunction can occur with age and can result in increased vascular tone, a reduction in vessel distensibility, and a decrease in tissue perfusion.38 Because there is a coincident decrease in retinal cells, this decrease in blood flow may be a response to decreased metabolic need.39,40

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