The inferior ophthalmic vein leaves the orbit posteriorly by: joining with the superior ophthalmic vein, passing through the superior orbital fissure on its own to join the cavernous sinus, or passing through the inferior orbital fissure to join with the pterygoid plexus of veins in the infratemporal fossa.
Because the ophthalmic veins communicate with the cavernous sinus, they act as a route by which infections can spread from outside to inside the cranial cavity.