Duma 1 EYE INJURY INCIDENCE AND MECHANISMS IN FRONTAL AUTOMOBILE CRASHES

The purpose of this study was to determine the incidence of eye injuries resulting from frontal automobile crashes and discuss the relevant injury mechanisms. In order to determine eye injury incidence, cases in NASS were selected from the years 1993 through 1999 that include drivers and front seat occupants only, while excluding ejected occupants and rollovers. In addition, only frontal impacts were considered, which are defined as having a primary direction of force (PDOF) of 11, 12, or 1 o’clock. The analysis included 10,770,828 front seat occupants from 22,236 cases for the years 1993 through 1999. An analysis of the cases indicates that 3.1% of occupants exposed to an airbag deployment sustained an eye injury, compared to 2.0% of those occupants not exposed to an airbag deployment. Moreover, there was a significant increase in the risk of corneal abrasion for occupants exposed to an airbag deployment (p=0.03). Although the risk of eye injuries increases with airbag exposure, this study illustrates that airbags reduce the incidence of orbital fractures. To analyze this, A new four level eye injury severity scale was developed that quantifies injuries based on recovery time, need for surgery, and possible loss of sight. A new finite element model of the eye was created using the LS-Dyna dynamic solver and was utilized to examine eye injury mechanisms. The model has the cornea and sclera defined as Lagrangian membrane elements and the liquid aquous humor and vitereous defined and Eulerian fluids. The model was validated using a range of impacting objects as velocities ranging from 12 m/s to 55 m/s. This model is the first model capable of correctly simulating the large deformation mechanics of blunt ocular trauma. Using the model, it was observed that highly localized strains in the cornea and ciliary body were most closely related to the severe injuries identified in the case studies. INTRODUCTION Although airbags have reduced the incidence of fatal and severe injuries in automobile collisions, they have been shown to increase the risk of less severe injuries.[1] These associated minor injuries include upper extremity fractures, skin abrasions, and eye injuries. In particular, the medical literature is replete with case studies on airbag induced eye injuries.[263] In addition to airbag induced eye injuries, Műller-Jensen et al. found broken windshield glass as a serious eye injury mechanism with 40% of these cases resulting in blindness in at least one eye.[60] The majority of these case studies focus on only a few occupants, however, four papers, in particular, include numerous cases of airbag induced eye injuries.[45,52,61,62] Duma, et al., present an analysis of 25 airbag induced eye injury cases that found the most serious injuries were a result of the occupant being struck by the airbag during deployment.[61] Ghafouri found bilateral injuries in 27% of 43 airbag induced eye injury cases.[62] Vichnin et al. report 14 cases and note that the most severe injuries were to occupants wearing eyeglasses, all of which sustained permanent ocular damage.[52] Stein et al. outline a detailed summary of the 97 published case studies that included a wide range of ocular injuries from corneal abrasions to ruptured globes.[45] There exists a paucity of experimental data on airbag induced eye injuries compared to the number of individual case study publications. Fukagawa et al. found that increased inflator aggressivity contributed to increased endothelial cell damage.[13] The most recent airbag related study examined the injury potential of high-speed foam particles released during airbag deployment.[63] This study illustrates the compounding risk of eye injuries from not only airbag contact, but also from particles released from the module during deployment. Orbital fractures have been reported in the literature occurring in sporting and other accidents, as well as in vehicle crashes.[64-67] Compared with the