The periorbita is the periosteal lining of the orbital bones. At the orbital apex, it fuses with the dura mater covering the optic nerve. Anteriorly, the periorbita is continuous with the orbital septum and the periosteum of the facial bones. The line of fusion of these layers at the orbital rim is called the arcus marginalis. The periorbita adheres loosely to the bone except at the orbital margin, sutures, fissures, foramina, tubercles, and canals. In an exenteration, the periorbita can be easily separated except where these firm attachments are present. Subperiosteal fluid, such as pus or blood, is usually loculated within these boundaries. The periorbita is richly innervated by sensory nerves.
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.