INCIDENCE

Ocular trauma in the United States occurs at an estimated rate of 2 million eye injuries per year (7 per 1000 population). Data gathered by McGwin et al.^3,⁴ from national ambulatory care surveys and hospital discharge records reveal that most eye injuries in the United States are treated in emergency departments (50.7%), followed by private physicians’ offices (38.7%), and outpatient (8.1%) and inpatient (2.5%) facilities. Demographic analysis of the highest-risk groups reveals that eye injury rates are highest among males in their 20s, with no clear difference among ethnic groups.

The rate of eye injury begins to climb later in childhood, with peak incidence in the third decade, followed by a slow decline. A second peak occurs with very advanced age.^4,⁵ This bimodal incidence in younger and older adults, as well as higher rates in males, is a reflection of the types of high-risk activities younger males engage in and the propensity for injuries and falls seen in older adults. These trends apply to injuries in these groups in general.

The setting in which an injury occurs has a marked impact on the severity and the prognosis for visual recovery. A study on the rate of eye injuries in the workplace reported that open globe injuries were the most common (46%), followed by injury to the surrounding ocular adnexal structures (20%), orbital fractures (11%), and traumatic hyphemas (11%).^4,⁶ Interestingly, the vast majority (approximately 90%) of eye injuries occur in settings where protective eyewear can have a major impact (e.g., workplace, sports activities). In fact, in many of these settings, eyewear is mandated but is not being worn at the time of injury. Thus, it is estimated that up to 90% of eye injuries could be prevented if protective eyewear were worn in these settings.

Of the small number of motor vehicle–related eye injuries (estimated at 1.8% of all eye injuries in the United States), very few present as open globe injuries. The mandated use of seatbelts has resulted in a twofold decrease in the number of eye injuries. Curiously, this has been offset by a twofold increase in eye injuries in accidents where airbags have been deployed. The most frequent injury mechanism related to MVA is impact with the windshield, followed by the airbag, steering wheel, and flying glass.⁷ However, these statistics must be viewed in the context of the decreased number of fatalities with the advent of airbag and seatbelt use.

Overall, only a small percentage (2.3%) of eye injuries encountered in the emergency setting present as lacerations and punctures (Table 1 and Figure 3). The most common causes of eye injuries in this setting are foreign bodies (44.6%) and blunt trauma (33.0%) (Table 2 and Figure 4).⁴ In the subgroup of patients with blunt trauma, many of these represent ruptures of the sclera that may not be clearly obvious to the examiner. In these cases, the examiner must rely on the key clinical findings associated with occult scleral rupture, as outlined in the section on diagnosis. Werner et al.⁵ reported on these occult scleral ruptures and found that they can represent up to 25% of all potential ruptured globes that present to physicians. Of these suspected cases of occult rupture, roughly one-third were actually found to have eye ruptures at the time of surgical exploration.

Table 1 Post-Traumatic Eye Findings in Emergency Setting

Type of Eye Injury	%
Contusion/abrasion	44.6
Foreign body	30.8
Conjunctivitis	10.2
Hemorrhage	9.9
Laceration	1.8
Puncture	0.5

Adapted from McGwin G Jr., Owsley C: Incidence of emergency department-treated eye injury in the United States. Arch Ophthalmol 123:662–666, 2005.

Figure 3 Post-traumatic eye findings in the emergency setting. See Table 1.

(Data from McGwin G Jr, Owsley C: Incidence of emergency department–treated eye injury in the United States. Arch Ophthalmol 123:662–666, 2005.)

Table 2 Key Mechanisms of Eye Injury in Emergency Setting

Mechanism of Eye Injury	%
Foreign body	44.6
Blunt trauma	33.0
Fire/burn	12.0
Machinery	3.1
Motor vehicle accident	2.3
Fall	1.8
Firearm	< 1.0

Adapted from McGwin G Jr, Owsley C: Incidence of emergency department-treated eye injury in the United States. Arch Ophthalmol 123:662–666, 2005.

Figure 4 Key mechanisms of eye injury in the emergency setting. See Table 2.

(Data from McGwin G Jr, Owsley C: Incidence of emergency department–treated eye injury in the United States. Arch Ophthalmol 123:662–666, 2005.)

There is a significant association of orbital fractures found in patients presenting with head trauma. In a large study of 4426 U.S. Army soldiers with facial and orbital fractures, orbital floor fractures were found in 26%. Within this group, there was also a 30% incidence of injury to the globe and a 70% incidence of concomitant bodily injury.⁸ Fractures of the orbital floor and medial wall make up the majority of fractures, with the lateral wall being the third most likely site of fracture and a smaller number of fractures occurring in the orbital roof (Figure 5).⁹ The floor is most susceptible just medial to the infraorbital groove, whereas the medial wall is most likely to rupture at the lamina papyracea, a paper-thin bony septum.¹⁰

Figure 5 Diagram of orbital bones with incidence of orbital fractures.

(Original image obtained from Yanoff M, Duker JS: Ophthalmology, 2nd ed. St. Louis, Mosby, 2004, Figure 83-1. Data from Shere JL, Boole JR, Holtel MR, Amoroso PJ: An analysis of 3599 midfacial and 1141 orbital blowout fractures among 4426 United States Army Soldiers, 1980–2000. Otolaryngol Head Neck Surg 130:164–170, 2004.)

MECHANISM OF INJURY

The mechanisms of injury to the eye and surrounding structures are largely associated with foreign bodies, blunt trauma, and thermal and chemical burns. Machinery, motor vehicle, and firearms are among the less common causes (see Table 2 and Figure 4).⁴ There is often appreciable overlap, and the physician must consider the impact of these mechanisms in combination and treat each injury individually. For example, a ruptured globe from blunt trauma may require a short course of systemic steroids for traumatic optic neuropathy if an afferent papillary defect is noted. Blunt force on an eye can also be described as coup–contrecoup, or compressive force in a manner similar to brain injury. Examples of coup injuries are corneal abrasions, subconjunctival hemorrhages, choroidal hemorrhages, and retinal necrosis. The best example of a contrecoup injury is commotio retinae, with anterior forces being transmitted to the retina and causing shearing of the retinal layers.¹¹ Compression of the globe usually causes scleral rupture. These open globe injuries are described below.

Orbital fractures can be caused by blunt forces with an increase of intraorbital pressure resulting in blowout fractures of the medial wall and floor, or caused by direct injury to the bones of the face resulting in fracture of any of the four walls. Because the lateral wall and roof are the most resistant to fracture, injury of these bones is an indicator of significant force to the face and eyes and concomitant injury to the globe should be carefully evaluated. Foreign body penetration of the orbit can involve the eye directly or any of the surrounding structures.

Chemical and thermal injuries to the eyelids and adnexa must be evaluated long term, well beyond the healing period for the superficial tissues. Burns to the eyelids and skin lead to scarring and contraction of the eyelids, which place these patients at risk for eyelid retraction and exposure damage to the cornea and ocular surface. Thus, long-term follow-up is important in this patient group, particularly if they are in a critical care setting. They must be treated with aggressive lubrication to the eyes until they demonstrate an ability to blink voluntarily and protect the eye. It is urged that all ICU and trauma wards have written eye care protocols for the management of these patients.

Open globe injuries are classically divided into penetrating and non-penetrating injuries. The latter group is caused by blunt trauma that causes a forceful compression of the eye and results in the physical rupture of the eye wall. The location of the rupture is typically in the areas where the eye wall is the thinnest, namely the corneo–scleral junction (the limbus), at the muscle insertion sites, and at the posterior attachment of the optic nerve. Ruptures posterior to the limbus may be difficult to identify and the clinician must be familiar with the signs of occult rupture, which are described in the section on diagnosis.

When the mechanism of injury involves penetration of the globe, the site of entry is usually visible and the decision for surgical intervention is straightforward. The three variables to consider when an entry wound is identified are whether the penetrating object has exited the eye, whether a foreign body is within the eye, or whether it has passed through the entire eye (perforation), in which case a posterior exit wound should be suspected and the foreign body may be located within the orbit.

If there is evidence of an intraocular or intraorbital foreign body, the type of material may also have implications in toxicity to the eye and the risk of infection to the orbit and the eye (Table 3). When the history of the type of injury is unclear, an orbital CT should be requested immediately and a shield placed over the eye. Even if the foreign body is easily accessible and protruding from the eye or surrounding structures, the emergency or trauma surgeon should make no attempt to remove the object. A shield should be carefully placed over the eye and no manipulation attempted. The extent of injury can be assessed at the time of surgical repair.

Table 3 Manifestations of Intraocular Metal Toxicity

DIAGNOSIS

Orbital Trauma

The key clinical features that aid in the decision for urgent management in cases of orbital trauma involve (1) significant limitation of ocular motility, (2) the presence of an afferent pupillary defect, (3) the presence of proptosis (abnormal anterior bulging of the eye), and (4) the presence of enophthalmos (abnormal posterior displacement of the eye). Any of these features requires an immediate orbital CT scan, ophthalmologic evaluation and consideration of surgical intervention. In a study by Lee et al.¹⁰ on the role of CT in orbital trauma, of those patients who suffered visual loss secondary to orbital trauma, the causes in order of decreasing frequency were retrobulbar hemorrhage, optic nerve thickening presumably secondary to edema, intraorbital emphysema, optic nerve impingement, retinal detachment, and ruptured globe. In addition to assessing the findings described previously the clinician should palpate the orbital rim for fractures (step-offs) and assess for hypoesthesia just below the eye in the distribution of the infraorbital nerve, and note the presence of hypoglobus (inferior displacement of the eye). Presence of hypoesthesia is indicative of a blowout fracture involving the infraorbital canal and nerve, but it has no urgent significance in itself.

Evaluation of ocular motility involves assessing for limitation of eye movement and eliciting symptoms consistent with decreased motility. The patient will often complain of double vision that disappears with the occlusion of one eye. Defining the orientation of the diplopia (horizontal, vertical, or oblique) can also help focus the exam. During the acute inflammatory period, ocular motility is often affected due to orbital congestion or muscle contusion, and supplementary tests can help distinguish between muscle palsy and muscle restriction or entrapment. Forced duction testing, where the eye is physically displaced using forceps to grasp the eye, can help discern the presence of mechanical restriction. A drop of anesthetic is placed on the eye and the patient is asked to look in the direction of the limited movement. The eye is then physically displaced in that direction to assess for a “tethering” effect (Figure 6). If significant resistance is encountered, entrapment must be suspected and an orbital CT should be obtained immediately. Clinical signs of entrapment supported by radiologic evidence require immediate surgical intervention to prevent muscle ischemia and necrosis.

Figure 6 Young male after blunt trauma to left eye. (A) Patient had limited ocular motility when looking left and possible entrapment on orbital CT (arrow). (B) Forced duction testing revealed full abduction, and entrapment was ruled out.

The finding of post-traumatic proptosis requires immediate measurement of eye pressures to assess for retrobulbar hemorrhage. Proptosis and elevated intraocular pressures are indicative of an orbital compartment syndrome and an axial and coronal orbital CT should be obtained immediately (Figure 7). The findings on further examination are resistance to retropulsion, diffuse subconjunctival hemorrhage, tight eyelids and orbit, vision loss, an afferent pupillary defect, and decreased color vision. Medical therapy should be initiated immediately with pressure-lowering agents as described in the management section in this chapter, and intraocular pressure should be measured frequently to ensure the efficacy of the medical therapy. If the pressures are very high (>30) or if there is no response to medical therapy, a lateral canthotomy and cantholysis should be performed (described in the management section). This can be performed prior to obtaining an orbital CT if pressures are significantly elevated and there is evidence of an afferent pupillary defect.¹²