The orbit is a bony socket of the facial skeleton formed around the optic nerve and eyeball. Each orbit is cone-shaped, with the apex pointing posteromedially so that the medial walls of the two orbits are almost parallel while the lateral walls are virtually perpendicular. Posteriorly, the orbit communicates with the cranial cavity via the superior orbital fissure and with the pterygopalatine fossa via the inferior orbital fissure – the optic canal lies more medial to these structures.

Bony walls

• The lateral wall separates the temporalis muscle from the eye and is formed by the zygomatic bone and greater wing of the sphenoid.
• The thin medial wall is mainly formed by the labyrinth of the ethmoid bone, lacrimal bone and frontal process of the maxilla. Inferiorly on the lacrimal bone (behind the inferomedial angle of the orbital rim) is the lacrimal fossa, a depression which houses the lacrimal sac.
• The roof is formed by the orbital plate of the frontal bone, separating the cranial and orbital contents.
• The floor is mostly maxilla. A large foramen for the nasolacrimal duct in the floor drains tears collected by the lacrimal sac into the nasal cavity.