Tomoyuki Kashima
Tomoyuki Kashima graduated from Medical school of Gunma University in 2002 and trained in general ophthalmology in Department of Ophthalmology in Gunma University. He achieved oculoplastic fellowship program in Seirei Hamamatsu Hospital, Shizuoka, Japan from 2005 to 2007. He became the chief of oculoplastic and orbit surgery in Gunma University from 2007, and also become council member of Asia Pacific Society of Ophthalmic Plastic and Reconstructive Surgery from 2010 to 2014. He achieved International fellowship program in UCLA Stein Eye Institute from 2015 to 2016.
Introduction
The characteristic physiology and anatomy of the orbit must be understood before considering how to care for a patient of orbital trauma [1]. Orbits have a typical structure which is surrounded by facial bones, and the only open direction is anterior. In addition, there are the optic nerve and many motor nerves, arteries, and veins in the orbit. After blunt or penetrating trauma to the eyeball and/or its surrounding tissue, these structures are easily damaged by direct insult and/or compressive pressure, which leads to severe subjective symptoms [2]. Therefore, to treat orbital trauma, the orbital structure should be understood.
Anatomy of the Orbit
The anatomy of the orbit is shown in Fig. 13.1. The structure has four walls, with the medial wall formed primarily by the orbital plate of ethmoid, as well as contributions from the frontal process of maxilla, the lacrimal bone, and a small part of the body of the sphenoid; the floor of the orbit (inferior wall) formed by the orbital surface of maxilla, the orbital surface of the zygomatic bone, and the minute orbital process of palatine bone; the lateral wall formed by the frontal process of zygomatic and more posteriorly by the orbital plate of the greater wing of sphenoid; and a roof (superior wall), formed primarily by the orbital plate frontal bone and also the lesser wing of sphenoid near the apex of the orbit. The medial wall and inferior wall of the orbit are located adjacent to the ethmoid and maxillary sinuses, respectively, and the two walls consist of very thin bones. Therefore, the medial and inferior walls are the most common sites of orbital fractures when blunt pressure is put on the orbit, causing injury to orbital contents, including not only bone, but also extraocular muscle and orbital fat extending into the sinus (Fig. 13.1). In contrast, the lateral wall, which consists of zygomatic, is very hard and thick and is more resistant to physical trauma [3]. Except as part of severe head trauma, the lateral wall is the least affected site in orbital blunt trauma. The ceiling of the orbit consists of the frontal bone. This bone is thin, but it is near the brain, and therefore, it is lined with thicker and harder tissue than the periosteum in other areas, including the maxillary or ethmoid sinus.
Fig. 13.1
Bony anatomy of the orbit. Left, photograph of the right orbit in a skull model. Right, the same photo with the names of bones inserted. The orbit has four walls, with the medial wall formed primarily by the orbital plate of ethmoid, as well as contributions from the frontal process of maxilla, the lacrimal bone, and a small part of the body of the sphenoid; the floor of the orbit (inferior wall) formed by the orbital surface of maxilla, the orbital surface of zygomatic bone, and the minute orbital process of palatine bone; the lateral wall formed by the frontal process of zygomatic and more posteriorly by the orbital plate of the greater wing of sphenoid; and a roof (superior wall), formed primarily by the orbital plate frontal bone and also the lesser wing of sphenoid near the apex of the orbit. The colored fields show the sites which are susceptible to orbital blunt pressure. The purple bone shows the orbital floor and the green bone shows the orbital medial wall. Yellow stars indicate the anterior and posterior ethmoidal foramen, which are passed by anterior and posterior arteries, veins, and nerves
Roof fractures are commonly seen in young children because of the prominence of the frontal bone. Because pneumatization of the frontal sinus does not occur until the age of 5–8 years, frontal fractures tend to extend superiorly into the skull. These patients should have neurosurgeon consultation as there is a high incidence of associated intracranial lesions.
Within the orbit, this confined compartment has many important structures, and the physiological function of each will be discussed before considering orbital trauma [4, 5]. Orbital soft tissues are connected and support each other through connective tissue septa, which is a dense tissue in the orbit. Orbital fat is both a filler in orbital tissue and a supportive tissue of orbital connective tissue [6]. The extraocular recti and oblique muscles adhere to the orbital bone and move in an interconnected manner by connective tissue serving as a pivot for each muscle (Fig. 13.2) [7]. Orbital trauma, including both fracture and foreign body, affects these structures, through dislocation and fixation of the orbital tissue, leading to prevention of eye movement. Therefore, the orbital fat and surrounding connective tissue are also important in the physiopathology of orbital trauma.
