Innovation Spotlight - Ocular Injuries

Nonpowder firearms can cause severe ocular injuries

With federal laws for airguns lacking, best defense may be increasing level of public awareness

By Cheryl Guttman
Reviewed by M. Lisa McHam, MD

Boston-Projectile sports are responsible for some of the most severe cases of sports-related eye trauma, according to M. Lisa McHam, MD. Focusing on events associated with nonpowder firearms, Dr. McHam noted that these guns account for the largest group of severe, preventable, sports-related eye injuries and often occur in the setting of unsupervised use and misuse by children. This information has important implications for prevention.

"Despite their potential for causing serious injury, airguns are often treated more like toys than firearms," Dr. McHam said. "There are no federal laws pertaining to airguns, and few states have laws regulating their sale or use.

"It has been suggested that polycarbonate protective eyewear, which will stop most airgun pellets, be included in the purchase of these guns," she said. "However, since most injuries occur in a disorganized setting, the impact of that preventive measure is doubtful.

"As ophthalmologists, we should contribute to increasing the level of public awareness about the risk of these guns because education is likely to be the most effective preventive tool," said Dr. McHam, who is an instructor, department of ophthalmology, Harvard Medical School, Boston.

Children often injured

The category of nonpowder firearms includes airguns that fire pellets (BBs) and paintball guns. Each year, about 32,000 nonpowder firearm injuries are reported in the United States, of which more than 60% occur in children and 5% to 8% involve the eye or orbit. Typically the victim and shooter are friends or relatives, 50% of the shootings are intentional to some extent, and in the preponderance of cases the guns are being used in an unstructured setting without adult supervision.

The vast majority of airguns sold generate muzzle velocities that exceed the level needed to penetrate the human cornea. Aside from the risk of perforating injury, the high-mass pellet fired combined with its relatively low velocity is associated with the potential for severe contusion defects.

The litany of blunt, nonperforating, airgun-related ocular injuries includes hyphema, iridodialysis, vitreous hemorrhage, commotio retinae, choroidal rupture, and cataract. Examiners should be aware, however, that these firearms are capable of causing significant intracranial and internal injury as well.

"In fact, most intracranial pellets gain entry via the orbit," Dr. McHam said. "This possibility must be ruled out with a history and physical examination, including neurologic assessment, before complete attention can be turned to the eye.

"However, recognize that history may be hard to elicit since the victim and perpetrator are often children engaging in activities they shouldn't have been," she said.

To rule out retained pellets, Dr. McHam recommended imaging studies with plain radiographs or CT, adding that MRI should not be performed because of the metallic nature of the foreign body.

Prognosis getting better

Perforating ocular injuries induced by airgun pellets generally carry a poor prognosis and have commonly necessitated enucleation. However, that situation may be changing for the better thanks to advances in surgical techniques, Dr. McHam said.

She noted that in a recent review of six cases of penetrating airgun pellet injury that had a relatively good outcome, Pulido and colleagues found exit wounds in or temporal to the macula were predictive of a poor outcome [Pulido JS, et al. Ophthalmic Surg Lasers 1997;28:625-632]. Visual acuity and the relative afferent pupillary defect at presentation were not related to the final visual outcome.

"These authors recommend closing the exit wound only if that is possible without globe distortion, since a vitreous plug will form an adequately sealed wound," Dr. McHam continued. "If light perception is present at 1 week, consider performing a secondary pars plana vitrectomy with lensectomy and possibly also a prophylactic scleral buckle."

Management of intraorbital pellets depends on their location. Removal is recommended for pellets that are anterior or epibulbar, both to prevent problems such as fistulas and to allow MRI studies in the future. Posterior pellets should be left alone unless problems related to their presence develop, such as infection, inflammation, or optic nerve impingement.

Piefly reviewing ocular injuries associated with paintball guns, Dr. McHam noted that these firearms generate a lower muzzle velocity than the pellet-firing airguns. However, the relatively large-size, paint-filled gelatin balls used allow transfer of the full force of impact to the eye with resultant risk of severe blunt injury and poor visual outcome.

Eye protection is generally required in the setting of organized paintball games, she added. However, players may intentionally remove their eyewear for a variety of reasons or it may become dislodged through contact with others, and such events have set the stage for most injuries occurring in the setting of organized games.

Disconcertingly, paintball guns and ammunition are easily obtainable by individuals and a growing number of paintball-related ocular injuries are occurring outside the setting of organized games, Dr. McHam concluded.

Ophthalmology Times / APRIL 15, 2000