Anatomy & Education
Orbital Anatomy
Orbital Anatomy
The orbit is a bony pyramid roughly 40 mm deep that houses and protects the eyeball, its six muscles, the optic nerve, and the lacrimal gland. Understanding orbital anatomy is essential for evaluating proptosis, orbital fractures, tumors, and the changes that occur in thyroid eye disease.
Overview
The orbit is shaped like a pear or four-sided pyramid with its apex pointing posteriorly toward the optic canal. It is widest approximately 1 cm behind the orbital rim. Volume is approximately 30 mL in adults, of which the globe occupies about 6.5 mL.
The four walls of the orbit — roof, floor, medial wall, and lateral wall — are each composed of different bones and have different clinical vulnerabilities. The medial wall and floor are the thinnest and most commonly fractured; the lateral wall is the thickest and most surgically accessible.
Orbital Bones
Seven bones contribute to the orbital walls. Click any bone in the interactive diagram below to identify it and learn its anatomical role.
Click any region to identify the orbital bones and foramina.
Frontal bone
Forms the orbital roof and supraorbital rim
Zygomatic bone
Forms the lateral wall and lateral orbital rim — the thickest, most accessible wall
Maxillary bone
