2020–2021 BCSC Basic and Clinical Science Course™
2 Fundamentals and Principles of Ophthalmology
Part I: Anatomy
Chapter 1: Orbit and Ocular Adnexa
The periorbital sinuses have a close anatomical relationship with the orbits (Fig 1-8). The medial walls of the orbits, which border the nasal cavity anteriorly and the ethmoid sinus and sphenoid sinus posteriorly, are almost parallel. In adults, the lateral wall of each orbit forms an angle of approximately 45° with the medial plane. The lateral walls border the middle cranial, temporal, and pterygopalatine fossae. Superior to the orbit are the anterior cranial fossa and the frontal sinus. The maxillary sinus and the palatine air cells are located inferiorly.
Figure 1-8 Coronal (A), sagittal (B), and axial (C) views of the anatomical relationship of the 4 periorbital sinuses.
(Illustrations by Dave Peace.)
Figure 1-9 Coronal computed tomography scan of the orbits and sinuses showing the maxillary and ethmoid sinuses. ES = ethmoid sinus; FE = fovea ethmoidalis; IT = inferior turbinate; MS = maxillary sinus; MT = middle turbinate; NS = nasal septum; Ost = ostium of the maxillary sinus; ST = superior turbinate; Strut = inferomedial orbital strut.
(Courtesy of William R. Katowitz, MD.)
The inferomedial orbital strut is located along the inferonasal orbit, where the orbital bones slope from the floor to the medial wall. This region is significant because of its proximity to the ostium of the maxillary sinus (Fig 1-9). In addition, the fovea ethmoidalis, which forms the roof of the ethmoid sinuses, is a lateral extension of the cribriform plate. The locations of the periorbital sinuses and their relation to anatomical features of the skull are indicated in Figure 1-8 and discussed further in BCSC Section 7, Oculofacial Plastic and Orbital Surgery.
Gospe SM 3rd, Bhatti MT. Orbital anatomy. Int Ophthalmol Clin. 2018;58(2):5–23.
Zide BM, Jelks GW. Surgical Anatomy Around the Orbit: The System of Zones. Philadelphia: Lippincott Williams & Wilkins; 2015.
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.