Automobile air bags, the inflatable devices designed

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1 Automobile air bags: friend or foe? A case of air bag-associated ocular trauma and a related literature review Kristin S. Kenney, O.D. a and Lisa M. Fanciullo, O.D. b a Associated Eye Surgeons, Plymouth, Massachusetts, and b VA Medical Center, West Roxbury, Massachusetts Background: Although air bags are placed in automobiles to act as safety devices, they have been shown to carry a risk of injury themselves. Ocular injury, in particular, can often be a direct consequence of air bag deployment. A case of ocular air bag injury is presented. A discussion and review of the current literature on this issue follows. Case Report: A 63-year-old man was transferred to our clinic after sustaining injuries related to a motor vehicle accident, during which the automobile s air bag was deployed. Initial examination revealed many signs of blunt ocular trauma of the O.D., including iridodialysis, dislocated lens with traumatic cataract, and traumatic/inflammatory glaucoma. Initial B-scan showed an attached retina O.D. One month later, the patient underwent an attempted pars plana vitrectomy with lensectomy, iris repair, and insertion of an anterior chamber intraocular lens. Complications arose during the procedure, and a total retinal detachment developed. Resultant acuity is no light perception O.D. Conclusions: Although ocular morbidity can be a direct consequence of air bag deployment, most eye injuries are minimal, and seem to be outweighed by the benefits of air bags. Drivers, as well as passengers, can minimize associated injuries by adhering to specific safety guidelines. This, as well as continual modification and improvement in air bag design, will maximize the safety of air bags and decrease the incidence of vision-threatening ocular injury caused by air bag deployment. Key Words: Air bag, blunt trauma, dislocated lens, iridodialysis, retinal detachment, traumatic glaucoma Kenney KS. Automobile air bags: friend or foe? A case of air bag-associated ocular trauma and a related literature review. Optometry 2005;76: Automobile air bags, the inflatable devices designed to provide a cushion between vehicle occupants and their steering wheel and dashboard, are becoming a less infrequent cause of blunt ocular trauma. While the air bag has been shown to reduce mortality and morbidity associated with high-speed motor vehicle collisions, 1 it has also been shown to cause ocular injury, ranging in severity from mild (e.g. lid lacerations and corneal abrasions) to sight-threatening, such as retinal detachment and traumatic optic neuropathy 2 (see Table). Air bags explode at speeds up to 200 MPH, and have the potential to cause both blunt trauma and chemical injury to the eye. Blunt trauma is by far the most common cause of ocular injury following air bag deployment and results in damage similar to that caused by a fist or a baseball. Blunt trauma can cause injury to the eye by three distinct mechanisms: 3 Coup refers to local trauma at the site of impact. Examples include corneal abrasions, subconjunctival hemorrhages, and retinal necrosis. Contrecoup describes injuries at the opposite side of the skull or eye from the site of impact. These injuries reportedly are caused by shock waves that traverse the brain/eye at the time of the injury. Damage may be found at different foci along the path of these shock waves. An example of an ocular contrecoup injury is commotio retinae. Ocular compression occurs when trauma resulting in a front-to-back compression of the eye causes an equatorial expansion of the globe to avoid rupture. There is usually an associated short-lived increase in intraocular pressure. When compression occurs, the lens

2 Table. Ocular injuries associated with blunt trauma Ocular structure Injury Lids/lashes Conjunctiva Cornea Glacoma Acute Glaucoma Late Iris Lens Retina Choroid Sclera Optic nerve TM, Trabecular meshwork and CB, ciliary body. Hematoma Laceration Orbital fracture Laceration Subconjunctival hemmorhage Abrasion Blood staining Angle recession Ciliary body injury Inflammatory trabeculitis Hyphema TM obstruction Direct damage to TM or CB Iridodialysis Vossius ring Cataract Subluxation Dislocation Commotio retinae Tears Detachment Retinitis sclopeteria Traumatic optic neuropathy zonules can be torn, leading to lens dislocation, or the iris can be torn away from the eye wall, resulting in an iridodialysis. Chemical burns (alkali keratitis) may also occur with air bag deployment as a result of contact of the alkaline compounds used in the air bag activation process with the cornea. 4 Long-term complications of this condition can range from scarring, corneal ulcer, and opacification to cataract and phthisis bulbi. Case Report A 63-year-old man was admitted to the emergency room following loss of consciousness (presumably due to a cardiac event) and subsequent Figure Patient s iridodialysis following air bag-associated ocular trauma O.D. motor vehicle accident. At the time of the collision, the patient s driver-side air bag did deploy. He remembered he was wearing sunglasses at the time of the accident, but was unable to tell us whether or not they broke. Clinical findings that night in the ICU revealed acuities of hand motion O.D. and 6/10 (measured with the Feinbloom low vision chart) O.S. All preliminary testing in the left eye was found to be normal, while the right eye displayed upper and lower lid ecchymosis, a subconjunctival hemorrhage, an edematous cornea, 2 cells in the anterior chamber with vitreous forward, a superior iridodialysis (draping very close, but not touching, the corneal endothelium), and an opaque crystalline lens dislocated inferiorly (see Figure). Pupils were normal OU, with no afferent pupillary defect. Tonopen intraocular pressures (IOPs) were O.D., 26 mmhg, 28 mmhg and O.S., 10 mmhg. A penlight held to the right lid gave a red reflex, but the fundus could not be visualized secondary to a vitreous hemorrhage. The patient was placed on the following regimen: 0.5% Timoptic q.12h. O.D. and Alphagan P q.12h. O.D. to control IOP; 1% Atropine q.d. O.D. and 1% Pred Forte q.4h. O.D. to control the inflammation; and 5% Muro 128 gtts q.i.d. O.D. to aid in corneal deturgescence. An eye shield was also provided. The following day, a B-scan showed an attached retina O.D., and IOP O.D. had normalized at 18 mmhg, 19 mmhg. 383

3 The plan at this point in time was to allow the vitreous hemorrhage to clear and the inflammation to subside (there was no immediate need for surgery, given the attached retina), and then to consider surgical remediation of the traumatic cataract and the iridodialysis. There was hope the patient would regain usable vision with a lens implant or a contact lens, since a diopter trial lens held in front of the right eye gave an acuity of 5/160 (the dislocated lens left the patient with a sizable aphakic zone centrally and superiorly). One month following his admission to the Critical Care Unit, the patient was scheduled to undergo a pars plana vitrectomy, pars plana lensectomy with posterior chamber intraocular lens implantation, and iris repair. At this time, the pressure O.D. had increased to 32, so a trabeculectomy was being considered as well. Unfortunately, during surgery that same week, an expulsive choroidal hemorrhage forced attempted lens extraction surgery to halt prematurely. At the patient s postoperative appointment, he was found to have light perception vision O.D. and an afferent pupillary defect in the same eye, with residual choroidal hemorrhage, a total retinal detachment, and large retinal tear superonasal to the optic nerve head. Although the iridodialysis had been repaired, the patient was left with the traumatic cataract still in place and a not-yet-completely-resolved vitreous hemorrhage O.D. The patient did eventually undergo choroidal drainage, a pars plana vitrectomy, and retinal repair with gas, but in the end was left with a no light perception and a phthisical eye (IOP 2 O.D.). Discussion and Literature Review Although air bags are meant to serve as protection for drivers and passengers of vehicles, they can cause severe injury, including ocular injury. In 1998, the American Academy of Ophthalmology recognized this problem and put forth the following statement: While air bags may cause eye injuries in low speed impacts, the number of lives saved by air bags during the high-speed impacts outweighs the risk of eye injury A review of the literature finds many studies investigating the risk vs. benefit of air bag impact on ocular structures, but one of the most extensive studies was that of Duma et al. 6 Duma et al. studied some 11 million front-seat occupants from over 22,000 cases between the years 1993 and His study was based on information from the National Automotive Sampling System Database, which classifies eye injuries into a system of severity levels, thus allowing a more accurate and standard estimation of ocular trauma. Of interest was that of all the study patients exposed to a deployed air bag, only 3% sustained an ocular injury. This should be compared to the 2% of motor vehicle accident victims, who experienced ocular injury when NOT exposed to an air bag. Duma et al. s extensive research and analysis led to the conclusion that, although vehicle occupants exposed to a deployed air bag had a higher risk of sustaining minor eye injuries (Duma s analysis shows a significant increase in the risk of corneal abrasion), the air bag provides an advantage by reducing the number of severe eye injuries. According to the Abbreviated Injury Scale (AIS) classification, this would include retinal detachment, corneal laceration, and hyphema, to name just a few. It is also of interest to note from Duma et al. s study that, while 29% of patients who sustained an air bag induced injury were wearing eyeglasses, 25% of those who did NOT sustain an ocular injury were also wearing glasses. Eyeglass wear did not prove to be a statistically significant finding. Interestingly, Vichnin et al. 2 concluded from a study of 14 cases that eyeglass wear may indeed pose a threat to vision when air bag trauma is introduced. Of 14 cases studied, three sustained serious and permanent ocular injury and all three were wearing eyeglasses. Similarly, a study out of Harvard Medical School in 1998 reported the results of 113 patients involved in air bag accidents. The study reported that most of the eye injuries sustained by the patients involved the superficial lid (81.8% of all ocular injuries) or the superficial cornea (11.8%). All of these superficial injuries resolved. The study did mention, however, that while sight-threatening injuries as a result of air bag deployment were rare, they did occur. 5

4 Although the most common ocular injuries following air bag deployment have been determined to be eyelid trauma, corneal abrasion, and hyphema, 7 there are certain subsets of the population that are at greater risk for development of more serious complications. One study found vehicle occupants 66 years of age and older to be 2 to 3 times more likely to incur an eye injury after air bag deployment secondary to increased stiffness of the crystalline lens, which produces up to a 120% greater stress in the ciliary body. 8 Likewise, those patients who have undergone refractive surgeries, including RK, PRK, and LASIK, are also more at risk for development of severe ocular injuries, secondary to compromised corneal integrity. 9,10 Lemley et al. 11 described a case of a 37-year-old woman who experienced a partial dislocation of the right corneal LASIK flap 17 months after the procedure, as a result of deployment of an air bag. Epithelial ingrowth then occurred that necessitated surgery. Eight months later, a rigid gaspermeable lens was fit in order to remediate the woman s vision to 20/20. The National Highway Traffic Safety Administration 12 has set forth guidelines in an effort to prevent or minimize air bag-associated injury. These guidelines are as follows: Drivers should never leave less than 10 between their breastbone and the center of the steering wheel. The closer the person is to the steering wheel, the greater force they will be subjected to on impact and the greater their chance for injury. Children less than 12 years of age and smaller or frail adults should ride properly restrained in the back seat. The safest place for a child to sit is in the middle of the back seat. Infants should NEVER ride in the front seat of a vehicle with a passenger-side air bag. Alarming statistic: While a passenger-side air bag lowers the mortality rate for adults involved in a motor vehicle accident, children less than 10 years of age have a 34% increased risk of mortality when that same air bag is deployed. 13 Seatbelts, both lap and shoulder belts, should ALWAYS be worn. Hands should be properly placed on either side of the steering wheel, in order to prevent a broken arm if air bag should deploy. Smoking while driving can lead to burns if the air bag deploys. Air bags should be inspected every 10 years. Air bags should be replaced immediately if they do deploy. Occupants of vehicles may obtain permission for an on-off switch for their air bags if there is a justifiable reason they cannot meet the above guidelines. It is important to realize that air bags do not take the place of seat belts. Air bags alone offer a minuscule decrease in injury risk when compared to the decrease in risk associated with the use of seat belts. Combined, the two offer the greatest benefit. 14 As eye care professionals, it is our responsibility to be aware of the ocular sequelae of air bag-related trauma, to be able to counsel our patients and to manage injuries appropriately. Although air bags are continually being researched and redesigned to improve effectiveness and safety, associated ocular trauma may actually increase as more and more vehicles become equipped with the devices. References 1. Graham JD, Thompson KM, Goldie SJ, et al. The costeffectiveness of air bags by seating position. JAMA 1997;278: Vichnin MC, Jaeger EA, Gault JA, et al. Ocular injuries related to air bag inflation. Ophthalmic Surg Lasers 1995; 26: Benson WE, Jeffers JB. Blunt trauma. In: Tasman W, Jaegar E, eds. Duane s clinical ophthalmology. Philadelphia: JB Lippincott Company, 2001;3: White JE, McClafferty K, Orton RB, et al. Ocular alkali burn associated with automobile air-bag activation. Can Med Assoc J 1995;153: Eye Health Services. Air bags: the life-changing consequences of a life-saving device. Eye Health Services Web site (2002) [last accessed Jan 24, 2004]: Duma SM, Jernigan MV, Stitzel JD, et al. The effect of frontal air bags on eye injury patterns in automobile crashes. Arch Ophthalmol 2002;120: Lee WB, O Halloran HS, Pearson PA, et al. Airbags and bilateral eye injury: five case reports and a review of the literature. J Emerg Med 2001;20: Hansen GA, Stitzel JD, Duma SM. Incidence of elderly eye injuries in automobile crashes: the effects of lens stiffness as a function of age. Ann Proc Assoc Adv Automot Med 2003;47: Uchio E, Kadonosono K. Are airbags a risk for patients after radial keratotomy? Br J Ophthalmol 2001;85:

5 10. Uchio E, Watanabe Y, Kadonosono K, et al. Simulation of airbag impact on eyes after photorefractive keratectomy by finite element analysis method. Graefe s Arch Clin Exper Ophthalmol 2003;241: Lemley HL, Chodosh J, Wolf TC, et al. Partial dislocation of laser in situ keratomileusis flap by air bag injury. J Refract Surg 2000;16: National Highway Traffic Safety Administration, U.S. Department of Transportation. Third Report to Congress: Effectiveness of Occupant Protection Systems and Their Use, 1996 [last accessed June 20, 2004]: /208con2e.html 13. Leuder GT. Air bag associated ocular trauma in children. Ophthalmology 2000;107: Croft A. Air bags: Saving lives at any cost? (1997) A Public Health Perspective. Dynamic Chiropractic 15(07) [online] [last accessed 2004 Jan 17, 2004]: Corresponding author: Kristin S. Kenney, O.D. Associated Eye Surgeons 45 Resnik Road Plymouth, Massachusetts kristinkenney@yahoo.com 386