Military Marking Round Injury to the Globe.

Marking cartridges are an increasingly popular form of nonlethal training munitions used primarily for military live-fire simulations. We report a case of ocular trauma due to such a projectile, resulting in the complete loss of vision and placement of a scleral shell. A 20-year-old man presented with decreased visual acuity in his right eye after being struck at close range by a marking cartridge during military training. Computed tomography imaging revealed a retained metallic foreign body within a deflated right globe, prompting emergent exploration and repair of the right globe. Postoperative course was complicated by pain and pruritis which resolved over a period of months. Nonlethal weapons, such as marking cartridges, are increasingly used for civilian crowd control as well as military and law enforcement training. Despite guidelines mandating the use of personal protective equipment with marking cartridges, eye protection may not be consistently used during simulated combat exercises. To the best of our knowledge, this is the first formal report of ocular injury due to this type of ammunition. Based on this case, we discuss other similar types of nonlethal munition used by military and law enforcement, their risks to the eye and orbit, and what steps may be undertaken to reduce future injury. Copyright:

INTRODUCTION

Although most commonly associated with law enforcement and crowd control, nonlethal weapons are becoming increasingly popular in police and military training. A subset of nonlethal weapons are kinetic impact projectiles (KIPs), defined as “weapons, devices, and munitions that are explicitly designed and primarily employed to incapacitate targeted personnel or materiel immediately, while minimizing fatalities, permanent injury to personnel, and undesired damage to property in the target area or environment.”[1] There have been many cases of eye trauma related to KIPs commonly used by police such as rubber stinger grenades, paintballs, airsoft pellets, and rubber bullets.[2345] Another type of nonlethal munition used for military live fire simulations is the marking round, composed of a polycarbonate projectile which leaves a colored marking compound upon impact and is designed to be worn with head, eye, throat, and groin protection. Given that, 16.9% of eye injuries suffered by the Department of Defense active-duty service members were due to gun and explosives training and handling, protection from ocular trauma is a priority for all military personnel.[6]

The authors describe a case of traumatic injury to the globe caused by nonlethal ammunition and subsequent management. This case report adhered to the ethical principles outlined in the Declaration of Helsinki as amended in 2013. Written consent was provided by the patient described in this case for the use of identifiable photos.

CASE REPORT

An otherwise, healthy 20-year-old Hispanic male presented with decreased visual acuity in his right eye after being struck with a nonlethal training munition. Earlier that day, the patient was participating in a military live-fire simulation at the United States Army installation. While in a dark room during the simulation, the patient briefly removed his safety goggles to wipe his brow and was subsequently struck by a polycarbonate training round from an M4 rifle fired inadvertently at a distance of approximately 5 m. Upon evaluation by ophthalmology following transfer from the military base's hospital, the patient's visual acuity in the right eye was only light perception with an associated relative afferent pupillary defect. Examination of the right eye revealed a soft globe with a stellate, inferonasal paracentral corneal laceration with protruding charred iris tissue, and a poorly formed anterior chamber containing a visible foreign body. Examination of the left eye was unremarkable. A review of computed tomography (CT) imaging of the orbits obtained during the initial evaluation at military hospital was notable for intravitreal air and a retained metallic foreign body within a misshapen, deflated right globe.

Emergent exploration and repair of the right globe were subsequently performed [Figure 1a]. Numerous foreign bodies were retrieved in the course of the globe exploration including a 3 cm wire, a metallic and plastic marking bullet, and numerous clumps of pink powder [Figure 1b]. In addition, iridectomy of charred, necrotic iris tissue containing gunpowder-like material was performed at the time of globe repair. The patient's postoperative course was complicated by pain and pruritis, which gradually subsided over a period of months with the help of oral narcotics and nonsteroidal anti-inflammatory drugs and the development of phthisical changes in the right eye. Given the patient's poor visual prognosis and poor esthetic appearance of the right eye, the patient was evaluated for the placement of a scleral shield versus enucleation. Considering the patient's lack of pain and his preference to avoid surgery on his phthisical eye, he was fitted with a scleral shell. On last noted follow-up, the patient remained stable following the placement of prosthesis.

Figure 1

Gross and schematic representation of the projectile and injury (a) intraoperative appearance of the affected eye showing penetration of the projectile through the cornea, (b) image of plastic-metal projectile extracted from the globe, (c) diagram of the components of a marking round

DISCUSSION

This study demonstrates the potential of plastic simulation ammunition to seriously and irreversibly damage unprotected ocular and orbital structures. The marking round is composed of a 0.45 g polycarbonate projectile with a colored marking compound housed inside. This assembly is stabilized by a metal sabot and propelled by smokeless gunpowder inside of an aluminum and steel cartridge case [Figure 1c]. In our case, both the plastic dome and metal sabot are visible lying transversely in the deflated right globe on CT scan [Figure 2]. The entire cartridge is designed to be fired from several commonly used military rifles retrofitted with a proprietary conversion kit. The projectile travels approximately 114 m/sand has a maximum range of 50 m. To mitigate serious injury, personal protective equipment for the head, eyes, neck, and groin is included with the munition and weapons conversion kits.

Figure 2

Unenhanced computed tomography appearance of retained metallic foreign body – two views, (a) coronal, (b) axial

Due to the complex construction of this type of munition, the oculoplastic surgeon must consider the many materials that comprise the marking pellet. The aluminum that comprises the sabot is known to be reactive in the eye but tends to cause minimal inflammation.[7] The marking compound often contains potentially irritating chemicals such as barium sulfate, sodium lauryl sulfate, and various dyes which should not pose a threat to the tissues of the eye and adnexa. Similarly, the smokeless powder used to propel the marking round contains primarily nontoxic nitrocellulose but also small amounts of diphenylamine and Centralite I, known ocular toxins.[8] These compounds can come in contact with eye and orbital tissue if, as in our case, the projectile is fired from a short distance away. Therefore, rapid accurate identification of the type of marking round is needed to ensure expedient removal in the operating room with copious irrigation of any areas which may have come in contact with the smokeless powder.

While not designed to produce lasting injury, Meyers describes a case of marking cartridge injury to the globe which resulted in traumatic cataract and significantly reduced visual acuity.[9] In a similar scenario as our case, this victim was a soldier participating in a simulated close-quarters firefight when he lost his polycarbonate safety glasses and was subsequently struck in his right eye at close range. Other reports of ocular injury from plastic projectiles come from Northern Ireland after the British military switched from using rubber bullets to plastic bullets in an effort to increase accuracy. Rocke compared victims of each type of projectile and found 14 instances of serious eye injury in the rubber bullet cohort and two instances in the plastic group.[10] Notably, one person died in the rubber bullet group, whereas three died in the plastic bullet group, a difference possibly explained by the plastic projectile increased accuracy in hitting its target. Airsoft pellets (also known as BBs) are another type of projectile, commonly used by law enforcement and the general public alike, with the potential to cause ocular trauma and blindness. Sternberg et al. described 22 patients with penetrating air gun-related eye injuries; 19 resulting in enucleation and the remaining three left with vision worse than 5/200.[4] This demonstrates that projectiles traveling with a fraction of the energy of a plastic or rubber bullet can still cause penetrating eye injuries in the absence of appropriate eye protection. Compared to structures in the lower body which all KIPs are designed to strike, the eye is particularly vulnerable since it lacks the protection of skin, soft tissue, or clothes.

Cities across the United States have recently experienced an increase in both social protests and police use of KIPs. About 20% of the US academic centers saw patients with suspected KIP-related ophthalmic injuries during the protests which occurred during the summer of 2020.[11] As the number and severity of these injuries became more apparent, the American Academy of Ophthalmology took an unprecedented step and issued their first-ever statement on a public policy position when they called on “domestic law enforcement officials to immediately end the use of rubber bullets to control or disperse crowds of protesters.”[12] We believe medical professionals have a duty to warn government agencies and the general public of the danger posed by these increasingly used nonlethal weapons.

Research quality and ethics statement

The authors followed applicable EQUATOR Network (http:// www.equator-network.org/) guidelines, notably the CARE guideline, during the conduct of this report.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that his name and initials will not be published and due efforts will be made to conceal his identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

This research was supported by an unrestricted grant from Research to Prevent Blindness unrestricted departmental award (Vanderbilt University Medical Center, Department of Ophthalmology and Visual Sciences).

Conflicts of interest

There are no conflicts of interest.