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TRAUMA/EMERGENCY RADIOLOGY Note: This copy is for your personal non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, contact us at www.rsna.org/rsnarights. 764 Injuries of the Globe: What Can the Radiologist Offer?1 Edward K. Sung, MD Rohini N. Nadgir, MD Akifumi Fujita, MD2 Cory Siegel, MD Roya H. Ghafouri, MD Anastasia Traband, MD Osamu Sakai, MD, PhD RadioGraphics 2014; 34:764–776 Published online 10.1148/rg.343135120 Content Codes: From the Departments of Radiology (E.K.S., R.N.N., A.F., C.S., O.S.), Ophthalmology (R.H.G., A.T.), and Otolaryngology–Head and Neck Surgery (O.S.), Boston Medical Center, Boston University School of Medicine, 820 Harrison Ave, FGH Building, 3rd Floor, Boston, MA 02118; and the Department of Radiology (A.F.), Jichi Medical University School of Medicine, Shimotsuke, Tochigi, Japan. Presented as an education exhibit at the 2012 RSNA Annual Meeting. Received June 3, 2013; revision requested July 11 and received August 19; accepted August 29. For this journal-based SA-CME activity, the author O.S. has disclosed financial relationships; the other authors, editor, and reviewers have no relevant relationships to disclose. Address correspondence to E.K.S. (e-mail: edward.sung@ bmc.org). 1 Current address: Department of Radiology, Boston Medical Center, Boston University School of Medicine, Boston, MA. 2 SA-CME LEARNING OBJECTIVES After completing this journal-based SACME activity, participants will be able to: ■■Describe normal ocular anatomy at CT and MR imaging. ■■List the advantages and disadvantages of various imaging modalities for evaluating globe injuries. ■■Discuss the various types of traumatic injuries of the globe and their potential mimics at CT and MR imaging. See www.rsna.org/education/search/RG. An earlier version of this article was published in print and contains an error in Figure 1. Traumatic ocular injuries are a significant cause of blindness and visual deficits. In the setting of acute orbital trauma, urgent ophthalmologic evaluation and intervention are critical in preserving vision. However, in the acute trauma setting, clinical evaluation of the globe may be difficult in the presence of surrounding periorbital soft-tissue swelling and other associated injuries, and patient cooperation may be limited because of unresponsiveness, altered mentation, or sedation. Often, rapid access to imaging is part of the initial diagnostic evaluation, and radiologists may be the first to identify traumatic injuries of the globe. Because of this, radiologists should be familiar with normal orbital and globe anatomy at various imaging modalities and have a thorough understanding of the various patterns of ocular injury and their imaging appearances. Radiologists should also be familiar with the various mimics of ocular injury, including congenital and acquired conditions that may alter the shape of the globe, various types of ocular calcifications, and the different types of material used to treat retinal detachment. Such knowledge may help radiologists make accurate diagnoses, which facilitates prompt and appropriate patient care. © RSNA, 2014 • radiographics.rsna.org Introduction Eye injuries account for approximately 3% of all emergency room visits in the United States (1,2). The World Health Organization estimates that eye injuries result in blindness in about 1.6 million people and unilateral blindness or decreased vision in almost 19 million people each year (3). Thus, it is apparent that eye injuries are a significant cause of disability, especially in young men, in whom ocular trauma is predominant (3–6). The overall prevalence of trauma-related eye injuries is approximately 2%–6%, with as many as 97% of cases resulting from blunt trauma (7,8). Common mechanisms of injury include motor vehicle accidents, sports-related accidents, industrial accidents, falls, and violent trauma (1,2,7–9). Patients with trauma-related facial fractures are at an increased risk for associated eye injuries, and the incidence of vision loss and blindness related to facial fractures may be as high as 10.8% (7,9–12). Ocular involvement may also be seen in as many as 84% of patients with head injuries (13). For this reason, the presence of facial fractures or head injuries should prompt a thorough assessment for potential ocular injury. RG • Volume 34 Number 3 Sung et al 765 Figure 1. Diagram shows normal ocular anatomy. AC = anterior chamber, C = cornea, CB = ciliary body, Ch = choroid, I = iris, L = lens, ON = optic nerve, PS = posterior segment (vitreous body), R = retina, Sc = sclera. Figure 2. Normal orbital anatomy. Axial unenhanced CT (a) and T1-weighted MR (b) images show normal orbital anatomy. AC = anterior chamber, C = cornea, CB = ciliary body, Ch = choroid, L = lens, LR = lateral rectus muscle, MR = medial rectus muscle, ON = optic nerve, PS = posterior segment (vitreous body), R = retina, Sc = sclera. Urgent ophthalmologic evaluation is important for prompt and appropriate management of ocular injuries (10,11). However, because of surrounding periorbital soft-tissue swelling and other associated injuries, physical examination of the globe may be difficult in the setting of acute trauma, and patient cooperation may be limited by unresponsiveness, altered mentation, or sedation. In the presence of such factors, imaging is necessary to assess the extent of injuries. Radiologists may be the first to identify any injuries of the globe; thus, knowledge of the various ocular injuries and their imaging appearances is crucial in making accurate diagnoses to guide proper patient treatment. In this article, we discuss the normal ocular anatomy, the various patterns of ocular injury and their imaging appearances, and potential mimics of injury. Normal Anatomy Understanding the normal anatomy and terminology of the globe is crucial to accurately identify and describe globe injuries (Fig 1). The globe consists of three layers: the sclera and cornea, which make up the protective outer layer of the globe and maintain its shape and pressure; the retina, which makes up the sensory inner layer; and the uveal tract, which makes up the middle vascular layer and contains the choroid, ciliary body, and iris (14). Often, the various layers of the globe are difficult to distinguish at imaging, especially computed tomography (CT) (Fig 2a). However, the sclera may be distinguished from the choroid at high-resolution magnetic resonance (MR) imaging (Fig 2b). The globe is also divided into anterior and posterior segments by the lens. The anterior segment 766 May-June 2014 radiographics.rsna.org contains aqueous humor and is further divided into anterior and posterior chambers, which are separated by the iris. The posterior chamber is often small and difficult to visualize at imaging. The posterior segment is posterior to the lens and contains vitreous humor. It is also known as the vitreous body. Imaging Modalities CT is the modality of choice for the initial evaluation of a traumatic injury to the globe, especially when intraorbital or intraocular foreign bodies are suspected (1,2,15–20). Access to CT scanners is widely available, and images may be rapidly acquired during evaluation of head injuries. CT also has excellent resolution of bones and soft tissue and easily depicts most foreign bodies. However, the presence of metallic foreign bodies or medical devices may cause streak artifact, which may obscure some findings. The main disadvantage of CT is its use of ionizing radiation. The increasing role of CT in medical imaging, especially in the acute trauma setting, has led to increased exposure to ionizing radiation. Therefore, every attempt to minimize radiation dose while maintaining image quality should be made, including modifying the scanning mode, voltage, current, exposure time, pitch, section thickness, and reconstruction algorithms (21). At our institution, orbital CT images are acquired helically from the frontal to the maxillary sinuses with the following parameters: 120 kVp, 100 mAs, 1.25mm section thickness with 1.25-mm intervals, and a pitch of 0.969. Images are reconstructed in soft tissue and bone kernels in both axial and coronal planes. Iterative reconstruction techniques are applied for further dose reduction, with resulting CT dose index values of 20 mGy or less. CT protocols vary among institutions, and optimal imaging parameters should be established by a joint effort among radiologists, technologists, and physicists. Ultrasonography (US) may also be performed to evaluate for globe injuries and may depict various ocular injuries, including hyphema, lens dislocations, globe rupture, intraocular foreign bodies, and vitreous and retinal hemorrhage (18,22,23). US is easily accessible and does not expose patients to ionizing radiation. However, the image quality is operator dependent, and US is considered contraindicated in those with suspected globe rupture (1,2,16,18,20,22,23). In addition, US is less sensitive than CT for depicting intraocular foreign bodies (18–20,22). Magnetic resonance (MR) imaging offers superior definition of orbital soft-tissue without the use of ionizing radiation (1,16). However, it may not be widely accessible, may be time-consum- Figure 3. Corneal laceration in a 12-year-old boy. Photograph shows a full-thickness corneal laceration with iris prolapse (arrow). ing, has poor definition of bone structures, and is contraindicated in those with metallic foreign bodies (1,2,15,16,18,20). Therefore, MR imaging is usually reserved for patients with suspected ocular injuries that are not readily apparent at CT, such as subtle open-globe injuries or organic foreign bodies (17,18,24–26). Conventional radiography may be used to evaluate for orbital fractures or radiopaque foreign bodies in the setting of a traumatic injury (1,2,27). However, its sensitivity for depicting fractures or foreign bodies is far less than that of CT, and it provides limited information on orbital soft tissues (1,2,27). Anterior Chamber Injuries Anterior chamber injures are often difficult to diagnose radiologically, and are usually more readily identified at clinical examination. Common injuries involving the anterior chamber include corneal lacerations and hyphema. Corneal Laceration Lacerations of the cornea are usually associated with penetrating trauma. The severity of the injury may vary, from superficial to deeper penetrating injuries. Superficial injuries are usually not apparent at imaging, but they may be readily identified at clinical examination (Fig 3). Corneal lacerations with complete penetration of the cornea may lead to globe rupture, which may be seen at CT as decreased volume of the anterior chamber (2,15,28). Hyphema Hyphema is defined as a collection of blood in the anterior chamber of the globe that usually results from disruption of the blood vessels in the iris or ciliary body (1,2,15). Usually, it is readily apparent at clinical examination as a blood-fluid level (Fig 4). At unenhanced CT, it may be seen as an area of hyperattenuation in RG • Volume 34 Number 3 Sung et al 767 Figure 4. Hyphema in a 26-year-old man. Photograph shows a blood-fluid level in the anterior chamber (arrow), a finding consistent with hyphema. Figure 5. Partial lens dislocation in a 70-year-old man. Axial unenhanced CT image shows a normally positioned left lens with an abnormal orientation (arrow), a finding consistent with partial lens dislocation. The left lens has relatively decreased attenuation compared with the normal right lens, a finding indicative of traumatic cataract. In addition, an area of hyperattenuation is seen in the anterior chamber (arrowhead), a finding consistent with hyphema. the anterior chamber (Fig 5) (1,2). Hyphema may also be readily identified at US; however, placing excessive pressure on the globe is not recommended in patients with hyphema (22). The presence of hyphema should prompt a search for other globe injuries. Lens Injuries The lens is surrounded by a capsule and suspended by radially oriented zonular fibers that are connected to the ciliary body. Blunt force that is applied to the globe in the anterior-posterior direction redistributes in the equatorial direction, which may cause the attachments of the zonular fibers on the lens to stretch and possibly tear. This mechanism can result in partial or complete dislocation of the lens (1,2,15). Partial Lens Dislocation A tear involving only one side of the zonular fibers leads to partial dislocation of the lens, in Figure 6. Posterior complete lens dislocation in a 72-year-old man. Axial unenhanced CT (a) and T2-weighted MR (b) images show the left lens, which is completely dislocated and dependently layered in the posterior segment of the left globe (arrow). which the lens is freely mobile on the side of the torn attachments but is still fixed on the side of the intact attachments, causing the lens to be oriented in an abnormal direction, usually with the torn segment dependently displaced. Displacement of the lens is readily identified at imaging (Fig 5) (1,2,15,22). Complete Lens Dislocation A tear involving all of the zonular fibers around the lens causes complete dislocation of the lens, which usually dislocates into the posterior segment and may be dependently layered in the posterior aspect of the globe at imaging (Fig 6) (1,2,15,22). Lens dislocation into the anterior segment is much less common because anterior movement of the lens is restricted by the iris (Fig 7) (15). 768 May-June 2014 radiographics.rsna.org Non-Traumatic Dislocation In the absence of trauma, lens dislocation may occur in patients with certain connective tissue disorders, such as Marfan syndrome, Ehlers-Danlos syndrome, and homocystinuria. In these cases, the dislocation is often bilateral (2). Patient history is important in distinguishing between traumatic and nontraumatic lens dislocation that is related to an underlying disorder. Traumatic Cataract Blunt trauma to the globe may also disrupt the lens capsule, which may lead to edema within the lens, which, in turn, may lead to the development of a cataract. Cataracts are readily identifiable at clinical examination (Fig 8). At CT, the affected edematous lens may appear relatively hypoattenuating compared with the nonaffected lens (Fig 5) (1). A mature cataract may be hyperattenuating or even calcified (29). Figure 7. Anterior complete lens dislocation in a 56year-old man. Axial unenhanced CT image shows anterior dislocation of the lens in the left globe (arrow). Posterior Segment Injuries The wall of the posterior segment of the globe is composed of three layers: the sclera, the outermost layer; the retina, the innermost layer; and the choroid, the middle vascular layer. Trauma to the globe may disrupt the attachments between these layers and result in detachments. Figure 8. Traumatic cataract in a 54-year-old man. Photograph shows a cataract (arrow) that was caused by an old traumatic injury. Retinal Detachment The retina, the innermost layer of the globe, is firmly attached to the ora serrata anteriorly and the optic disc posteriorly. A traumatic tear in the retina allows vitreous fluid and blood to collect between the retina and choroid, resulting in detachment of the retinal layer. Because of the firm retinal attachments at the optic disc, retinal detachments may have a characteristic V-shaped appearance at imaging, with the apex at the optic disc (Figs 9, 10) (1,2,22). Choroidal Detachment The choroid is a vascular layer located between the retina and sclera. When a traumatic injury results in decreased ocular pressure, the pressure within the suprachoroidal space also decreases, which allows fluid or blood to accumulate and results in detachment of the choroidal layer. Usually, choroidal detachments have a lentiform or biconvex shape at imaging and spare the posterior portion of the globe (Fig 11) (1,2,22). Vitreous Hemorrhage Trauma to the globe may disrupt retinal blood vessels and result in hemorrhage in the vitreous humor of the posterior segment. Vitreous hemorrhage is readily seen at CT as hyperattenuating fluid in the posterior segment (Fig 12) (1,2). It may also be seen at US; however, severe vitreous hemorrhage may obscure other ocular findings (22). Open-Globe Injuries Open-globe injuries, also known as globe rupture, are a major cause of blindness (1–3,28). Blunt trauma to the globe can disrupt the integrity of the sclera and result in globe rupture. Scleral tears from blunt trauma typically occur behind the insertions of the extraocular muscles, where the sclera is thinnest (1,2). Penetrating injuries may also disrupt the sclera and, when they are deep enough, lead to globe rupture. Open-globe injuries related to blunt trauma are more frequently seen in women, whereas those related to penetrating trauma are more frequently seen in men (3). CT is the initial imaging modality of choice in the setting of ocular trauma with a suspected open-globe injury (2,15,26,28). Its sensitivity for depicting an open-globe injury is approximately 56%–75% when the injury is clinically suspected and 56%–68% when it is clinically occult (2,15,28). MR imaging may provide more detailed information about the globe and should be considered when a clinically suspected open-globe injury is not identified at CT. RG • Volume 34 Number 3 Sung et al 769 Figures 9, 10. (9) Retinal detachment in a 69-yearold woman. US image shows a complex fluid collection (arrow) in the posterior aspect of the globe. (10) Retinal detachment in an 82-year-old man. Axial unenhanced CT (a) and fluid-attenuated inversion-recovery (FLAIR) MR (b) images show a V-shaped fluid collection (arrows) in the posterior segment of the right globe, with the apex at the optic disc. The fluid collection is hyperattenuating at CT and hyperintense at FLAIR MR imaging, a finding consistent with hemorrhage. Note that the right lens was replaced. Figure 11. Choroidal detachment in a 75-yearold woman. Axial unenhanced CT image shows hyperattenuating fluid along the lateral and medial margins of the posterior segment of the right globe (arrows) with sparing of the most posterior portion of the globe. Note that the right lens was replaced. Figure 12. Vitreous hemorrhage in a 92-yearold woman. Axial unenhanced CT image shows near-homogeneous hyperattenuation in the posterior segment of the right globe (arrow), a finding consistent with vitreous hemorrhage, and periorbital soft-tissue swelling (arrowheads). 770 May-June 2014 radiographics.rsna.org Figure 13. Open-globe injury in a 68-year-old woman. Axial (a) and coronal (b) unenhanced CT images show an abnormal contour of the left globe (arrows), a finding consistent with globe rupture. Figure 14. Open-globe injury in a 48-year-old man. (a) Axial unenhanced CT image shows slight flattening of the posterior aspect of the right globe (arrow) and adjacent vitreous hemorrhage. (b) Coronal unenhanced CT image shows a more obvious contour abnormality of the right globe (arrowhead), a finding consistent with globe rupture. Figure 15. Open-globe injury resulting from a gunshot wound in a 20-year-old man. Photograph (a) and axial unenhanced CT image (b) show complete rupture of the left globe (arrow in b). Metallic bullet fragments are seen in the left periorbital soft tissues (arrowhead in b). In general, US is considered to be contraindicated when an open-globe injury is suspected (1,2). Direct Signs of Open-Globe Injury Direct imaging findings of open-globe injuries include alteration of the globe contour or volume and evidence of scleral discontinuity (Fig 13) (1,2,15,28). These findings may range in conspicuity from obvious to very subtle, and evaluation of the globe in multiple planes may be useful (Fig 14). Obvious cases are often related to severe trauma, such as a gunshot wound (Fig 15). When a clinically suspected open-globe injury is not readily identified at CT, MR imaging has been shown to have increased sensitivity in depicting subtle areas of scleral discontinuity (26). Indirect Signs of Open-Globe Injury One indirect imaging finding of open-globe injuries is alteration of the anterior chamber depth. Anterior chamber depth may increase when RG • Volume 34 Number 3 Sung et al 771 Figure 16. Open-globe injury in a 44-yearold man. Axial unenhanced CT image shows that the depth of the anterior chamber of the left globe (arrow) is slightly increased compared with the right side. Punctate areas of hyperattenuation are seen in the posterior segment (arrowhead), a finding consistent with vitreous hemorrhage. Figure 17. Open-globe injury in a 30-year-old man with an intraocular foreign body. Axial unenhanced CT images obtained at the level of the lens (a) and more superiorly (b) show a metallic foreign body (arrow in a) and air (arrowheads in b) in the posterior segment of the right globe. The shape of the right globe is relatively preserved. the sclera in the setting of a traumatic injury (Fig 17) (1,2,15,28). Mimics of Open-Globe Injury Figure 18. Coloboma in a 35-year-old man. Axial unenhanced CT image shows that the posterior aspect of the right globe has an abnormal contour (arrow), a finding consistent with coloboma. a rupture is present in the posterior segment, which decreases pressure and volume and allows the lens to sink posteriorly (Fig 16) (1,2,15,28). Conversely, decreased anterior chamber depth may result from a severe corneal laceration, which leads to decreased volume in the anterior segment (2,15,28). Another indirect finding of open-globe injuries is an intraocular foreign body or air, which implies penetration through Radiologists should be familiar with nontraumatic mimics of open-globe injuries, which include congenital and acquired deformities of the globe such as coloboma, staphyloma, congenital glaucoma, an elongated globe from myopia, and phthisis bulbi (Figs 18–20) (1,2,15). Mass effect from an orbital mass or hematoma may also alter the globe contour (2,15). In addition, radiologists should not mistake ocular calcifications or the material used to treat retinal detachment as an intraocular foreign body. Intraocular Foreign Bodies In the United States, an average of 3.1 penetrating eye injuries occur per 100,000 person-years (6). Common mechanisms of injury include violent trauma, motor vehicle accidents, recreational accidents, and work-related industrial accidents (6). Intraorbital foreign bodies are present in approximately 10%–17% of all ocular injuries, and intraocular foreign bodies may be present in 772 May-June 2014 radiographics.rsna.org Figures 19, 20. (19) Myopia-related globe elongation in a 71-year-old man. Axial unenhanced CT image shows that both globes have an elongated contour (arrow). (20) Phthisis bulbi in a 75-year-old woman. Axial unenhanced CT image shows that the right globe is shrunken and calcified (arrow), a finding consistent with phthisis bulbi and the result of an old injury. Figures 21, 22. (21) Intraocular foreign body in a 48-year-old man. Axial unenhanced CT image shows a metallic foreign body in the anterior chamber of the left globe (arrow). (22) Intraocular foreign body in a 56-year-old man with nailgun injuries. Frontal radiograph (a) and axial unenhanced CT image (b) show a nail in the scalp and another extending into the right globe (arrow in b). as many as 41% of open-globe injuries (20,30). Identification of intraocular foreign bodies is important because they may lead to infection, retinal toxicity, or vision loss if not appropriately treated. The location of an intraocular foreign body may vary, but they are most commonly seen in the posterior segment (20). CT is the imaging modality of choice when intraorbital or intraocular foreign bodies are suspected (1,2,17–20,22,25,30). Its sensitivity for depicting foreign bodies varies widely depending on the type and size of foreign bodies present, but it may be as high as 100% (20). MR imaging is contraindicated in the presence of a metallic foreign body but is more sensitive than CT in depicting organic material (17,18,25). US may also depict intraocular foreign bodies, but it is less sensitive than CT, and intraocular air may mimic a foreign body (22). The rate of conventional radiography for depicting intraorbital and RG • Volume 34 Number 3 Sung et al 773 Figure 23. Intraorbital plastic foreign body in a 48-year-old man. Coronal (a) and sagittal (b) unenhanced CT images show a plastic chopstick in the right orbit (arrows) and extending intracranially through the orbital apex. Figure 24. Intraorbital wooden foreign bodies in an 82-year-old woman. Axial unenhanced CT image shows linear hypoattenuating foreign bodies in the left orbit (arrows), a finding consistent with a known penetrating trauma from wooden foreign bodies. intraocular foreign bodies ranges from 40% to 90% and depends on the type of material present (20,27). In general, the sensitivity of radiographs for depicting intraocular foreign bodies is lower than that of CT; however, it may be as high as 96% when there is clinical evidence of a penetrating ocular injury (27). Still, radiographs play a limited role in the setting of acute trauma because they provide little information about the orbital soft tissues. Types of Foreign Bodies Intraorbital foreign bodies may be inorganic or organic. Inorganic foreign bodies are more frequently encountered and most commonly include metal and glass (17,19,20,30,31). Usually, they are associated with vision loss and, because they are inert, do not elicit an inflammatory response (17). Metal is readily identified at CT (Figs 17b, 21, 22). However, because glass may vary in composition, its attenuation at CT also varies (18). CT is still considered the imaging modality of choice and has been shown to depict as many as 96% of glass foreign bodies that are at least 1.5 mm and as many as 48% of glass foreign bodies that are 0.5 mm (18). Another type of inorganic foreign body that may be encountered is plastic, which is hyperattenuating—but not as hyperattenuating as metal—at CT (Fig 23). The most commonly encountered organic foreign body is wood (17). Organic foreign bodies may elicit a marked inflammatory response and may cause a severe infection (17,25,30,31). If they are initially undiagnosed, chronic or recurrent orbital infections may result (30). Detecting wood at CT may be difficult because it appears hypoattenuating in the acute phase, an appearance that mimics that of air (Fig 24) (1,2,17,24,25,30). Typically, wood has a geometric shape, a feature that may help distinguish it from air (1). In addition, its attenuation may change over time, from isoattenuating relative to orbital soft tissue in the subacute phase to hyperattenuating in the chronic phase (25,30). When a wooden foreign body is clinically suspected and not apparent at initial CT, MR imaging may depict inflammation, which is commonly associated with organic foreign bodies (1,17,18,24,25). Mimics of Intraocular Foreign Bodies Radiologists should be familiar with different patterns of ocular calcifications, as well as the appearance of the various materials used to treat retinal detachment to avoid misdiagnosing a foreign body or other orbital injury. Calcifications that occur 774 May-June 2014 Figure 25. Optic drusen in a 42-year-old woman. Axial unenhanced CT image shows a punctate calcification near the optic disc in the right globe (arrow), a finding consistent with an optic drusen. radiographics.rsna.org Figure 26. Scleral plaques in a 90-year-old woman. Axial unenhanced CT image shows scleral calcifications at the insertion sites of the medial and lateral rectus muscles (arrows), a finding consistent with scleral plaques. Figure 27. Scleral band in a 40-year-old man. Axial (a) and coronal (b) unenhanced CT images show a hyperattenuating band (arrows) around the right globe, a finding consistent with a scleral band. near the optic disc are referred to as optic drusen and are associated with macular degeneration (Fig 25). They may be a cause of benign pseudopapilledema (32). Calcifications that occur along the insertions of the medial and lateral rectus muscles are known as scleral plaques and are commonly seen in elderly patients (Fig 26) (32). The lens may also be calcified from a cataract. These ocular calcifications should not be mistaken for intraocular foreign bodies. Common materials used to treat retinal detachment include scleral bands, silicon oil, and gas (Figs 27–30) (2,32). Blast Injuries Radiologists should also be aware of the potential for ocular involvement in blast injuries. Although explosions are rare in industrial and recreational accidents, the increasing rate of terrorist- and combat-related explosions have increased the likelihood that health-care providers will encounter these injuries (33–35). Injuries from a blast may be primary or secondary. Primary blast injuries result from the high-pressure blast waves generated from an explosion, which cause direct tissue damage (35). Secondary blast injuries result from debris that is physically displaced by the blast wave (35). Ocular injuries may occur in 10%–28% of blast injuries (34,35). Among blast survivors, most ocular injuries result from penetrating or blunt trauma from debris from a blast wave (a secondary blast injury) (34,35). The patterns of ocular blast injuries vary; the most common injuries include corneal lacerations, open-globe RG • Volume 34 Number 3 Sung et al 775 Figure 28. Intraocular silicon oil in a 79-year-old man. Axial unenhanced CT image shows hyperattenuating material (arrow) in the posterior segment of the left globe, a finding consistent with silicon oil. Figure 29. Intraocular silicon oil in a 79-year-old man. Axial T1-weighted (a) and T2-weighted (b) MR images show material in the posterior segment of the right globe (arrow) that is isointense at T1-weighted imaging and hypointense at T2-weighted imaging, a finding consistent with silicon oil. Figure 30. Intraocular gas from pneumatic retinopexy in a 44-year-old woman. Axial unenhanced CT image shows hypoattenuating gas with attenuation similar to that of air layering in the nondependent portion of the posterior segment of the left globe (arrow), a finding consistent with prior pneumatic retinopexy. cal evaluation may be challenging in the acute trauma setting. Often, CT is the initial imaging modality of choice in the setting of traumatic facial injuries, and radiologists may be the first to diagnose ocular injuries. Familiarity with the various types of ocular injuries and their imaging appearances, as well those of potential mimics of injury, are crucial in making accurate diagnoses that will appropriately guide patient care. injuries, intraocular foreign bodies, and vitreous hemorrhage (33–35). Radiologists should thoroughly evaluate the globes for any type of injury in patients who sustained a blast. Conclusions Ocular injuries are fairly common and are a significant cause of blindness and vision deficits. Urgent ophthalmologic evaluation is critical to prevent permanent visual deficits, but physi- Disclosures of Conflicts of Interest.—O.S.: Related financial activities: receives royalties from McGraw-Hill and honoraria for lectures from Bracco Diagnostics, Inc, and Kyorin USA, Inc. Other financial activities: none. 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Emerg Radiol 2003;10(3): 144–146. 27.Saeed A, Cassidy L, Malone DE, Beatty S. Plain xray and computed tomography of the orbit in cases and suspected cases of intraocular foreign body. Eye (Lond) 2008;22(11):1373–1377. 28.Kim SY, Lee JH, Lee YJ, et al. Diagnostic value of the anterior chamber depth of a globe on CT for detecting open-globe injury. Eur Radiol 2010;20(5): 1079–1084. 29.Bron AJ, Vrensen GF, Koretz J, Maraini G, Harding JJ. The ageing lens. Ophthalmologica 2000;214(1): 86–104. 30.Boncoeur-Martel MP, Adenis JP, Rulfi JY, Robert PY, Dupuy JP, Maubon A. CT appearances of chronically retained wooden intraorbital foreign bodies. Neuroradiology 2001;43(2):165–168. 31.Nasr AM, Haik BG, Fleming JC, Al-Hussain HM, Karcioglu ZA. Penetrating orbital injury with organic foreign bodies. Ophthalmology 1999;106(3): 523–532. 32.LeBedis CA, Sakai O. Nontraumatic orbital conditions: diagnosis with CT and MR imaging in the emergent setting. RadioGraphics 2008;28(6): 1741–1753. 33.Erdurman FC, Hurmeric V, Gokce G, Durukan AH, Sobaci G, Altinsoy HI. Ocular injuries from improvised explosive devices. Eye (Lond) 2011;25(11): 1491–1498. 34.Morley MG, Nguyen JK, Heier JS, Shingleton BJ, Pasternak JF, Bower KS. Blast eye injuries: a review for first responders. Disaster Med Public Health Prep 2010;4(2):154–160. 35.Wolf SJ, Bebarta VS, Bonnett CJ, Pons PT, Cantrill SV. Blast injuries. Lancet 2009;374(9687):405–415. TM This journal-based SA-CME activity has been approved for AMA PRA Category 1 Credit . See www.rsna.org/education/search/RG. Teaching Points May-June Issue 2014 Injuries of the Globe: What Can the Radiologist Offer? Edward K. Sung, MD • Rohini N. Nadgir, MD • Akifumi Fujita, MD • Cory Siegel, MD • Roya H. Ghafouri, MD • Anastasia Traband, MD • Osamu Sakai, MD, PhD RadioGraphics 2014; 34:764–776 • Published online 10.1148/rg.343135120 • Content Codes: Page 768 Because of the firm retinal attachments at the optic disc, retinal detachments may have a characteristic V-shaped appearance at imaging, with the apex at the optic disc (Figs 9, 10) (1,2,22). Page 768 Usually, choroidal detachments have a lentiform or biconvex shape at imaging and spare the posterior portion of the globe (Fig 11) (1,2,22). Page 770 One indirect imaging finding of open-globe injuries is alteration of the anterior chamber depth. Page 771 Radiologists should be familiar with nontraumatic mimics of open-globe injuries, which include congenital and acquired deformities of the globe such as coloboma, staphyloma, congenital glaucoma, an elongated globe from myopia, and phthisis bulbi (Figs 18–20) (1,2,15). Mass effect from an orbital mass or hematoma may also alter the globe contour (2,15). Page 773 Detecting wood at CT may be difficult because it appears hypoattenuating in the acute phase, an appearance that mimics that of air (Fig 24) (1,2,17,24,25,30).