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INTRODUCTION AND EPIDEMIOLOGY
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The breadth of ocular emergencies seen in the ED requires solid examination skills and an understanding of basic differential diagnosis. A recent review1 of 1400 ED ocular emergencies identified the following conditions: ocular trauma in 27%, of which 73% involved corneal abrasions, 6% involved blunt eye trauma, and 5% involved a corneal foreign body; the second most common condition was conjunctivitis (15%), and retinal problems and glaucoma involved 6%.
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This chapter reviews eye anatomy, the essential skills needed for the ED eye examination, and common ophthalmic medications. Common causes of the red eye, ocular infections and inflammation, trauma to the eye, acute visual reduction or loss, and acute cranial nerve palsies are discussed. The principles and advantages of ocular US are summarized.
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The orbit is a pyramid of bony walls that converge to an apex posteriorly. The orbit is bordered superiorly by the frontal sinus, medially by the ethmoid sinus, inferiorly by the maxillary sinus, and laterally by the zygomatic bone. The ethmoid bone (lamina papyracea) is paper thin and is the most likely sinus wall to break in blunt eye trauma or to be perforated due to sinusitis with subsequent spread of infection to the orbit. The orbital contents include the ocular muscles, retroseptal fat, and the optic nerve, whereas the globe is considered a separate entity.
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The anterior limit of the orbital cavity is the orbital septum, which is a layer of fascia extending from the periosteum along the orbital rim to the levator aponeurosis of the upper eyelid and to the edge of the tarsal plate of the lower eyelid. Abnormalities, such as the accumulation of blood or infection, are referred to as "preseptal" or "postseptal." Postseptal conditions are extremely serious. The septum is generally impervious to bacteria, which serves to limit spread of infection from the facial skin into the orbit (Figure 241-1). All nerves and vessels of the eye enter through the apex of the orbit, which is also the site of origin for the extraocular muscles. The optic nerve is subject to compression from mass effect due to tumors, abscesses, or hematomas.
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The arterial blood supply of the eye and orbit is the ophthalmic artery, the first major branch of the intracranial portion of the internal carotid artery, which enters the orbit beneath the optic nerve. The central retinal artery is the first intraorbital branch of the ophthalmic artery and courses through the optic nerve. The venous drainage of the eye and orbit is through the ophthalmic veins, which drain into the central retinal vein. The ophthalmic veins communicate ...