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 1993-9 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 of 11, 12, or 1 o'clock. The analysis included 10,770,828 front seat occupants from 22,236 cases for 1993-9. 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 at 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. For the covering abstract see ITRD E825082.
Samenvatting