2020–2021 BCSC Basic and Clinical Science Course™
2 Fundamentals and Principles of Ophthalmology
Part I: Anatomy
Chapter 1: Orbit and Ocular Adnexa
Medial Orbital Wall
The medial wall of the orbit is formed from 4 bones (Fig 1-3):
frontal process of the maxillary bone
orbital plate of the ethmoid bone
lesser wing of the sphenoid bone
The ethmoid bone makes up the largest portion of the medial wall. The fossa for the lacrimal sac is formed by the frontal process of the maxillary bone and the lacrimal bone. Below, the fossa is continuous with the bony nasolacrimal canal, which extends into the inferior meatus (the space beneath the inferior turbinate) of the nose.
The orbital plate of the ethmoid bone, which forms part of the medial orbital wall, is a paper-thin structure—hence its name, lamina papyracea—and is the most common site of fracture following blunt trauma to the orbit. The medial wall has 2 foramina, which can act as conduits for processes involving the ethmoid sinus to enter the orbit.
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.