Medial Wall of the Orbit
The medial wall of the orbit is composed of the orbital plate of the ethmoid bone, the lacrimal bone, the frontal process of the maxillary bone, and the lesser wing of the sphenoid bone. Of these, only the lacrimal bone is wholly within the orbital confines. The medial wall of the orbit is located adjacent to the ethmoid and sphenoid sinuses and nasal cavity. The medial wall of the optic canal is formed by the lesser wing of the sphenoid, which is also the lateral wall of the sphenoid sinus.
An important landmark is the frontoethmoidal suture, which marks the approximate level of the cribriform plate, the roof of the ethmoids, the floor of the anterior cranial fossa, and the exit of the anterior and posterior ethmoidal arteries from the orbit.
The thinnest walls of the orbit are the lamina papyracea, between the orbit and the ethmoid sinuses along the medial wall, and the maxillary bone, particularly in its posteromedial portion. These are the bones most frequently fractured as a result of indirect, or blowout, fractures (see Chapter 6 in this volume). Acute bacterial infections of the ethmoid sinuses may extend through the lamina papyracea or neurovascular perforations to form a subperiosteal abscess and extend into the orbital soft tissues.
Figure 1-2 Orbital bones, internal views. A, Lateral wall. B, Medial wall.
(Modified with permission from Dutton JJ. Atlas of Clinical and Surgical Orbital Anatomy. Philadelphia: Saunders; 1994:9–10.)
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.