Finite element analysis of changes in tensile strain and deformation by airbag impact in eyes of various axial lengths

PURPOSE: Airbags have substantially reduced mortality and morbidity, while ocular injuries caused by airbags have been reported. We applied a three-dimensional finite element analysis (FEA) model we have established for evaluation of the deformation of an intact eyeball of various axial lengths induced by an airbag impact at various impact velocities. METHODS: A model human eye we have created was used in simulations with an FEA program, PAM-GENERIS™ (Nihon ESI, Tokyo, Japan). The airbag was set to impact eyes with various axial lengths of 21.85 mm (hyperopia), 23.85 mm (emmetropia) and 25.85 mm (myopia), at initial velocities of 30, 40, 50 and 60 m/s. Changes in the shape of the eye and the strain induced were calculated. Deformation of the eye in a cross-sectional view was displayed sequentially in slow motion. RESULTS: We found that considerable damage, such as corneal or scleral lacerations, was observed especially at higher impact velocities, such as 50 or 60 m/s, in eyes with any axial length. Deformation was most evident in the anterior segment. The decrease rate of axial length was greatest in the hyperopic eye, followed by the myopic eye, and the emmetropic eye. CONCLUSIONS: It was shown that hyperopic eyes are most susceptible to deformation by an airbag impact in this simulation. The considerable deformation by an airbag impact on the eye during a traffic accident shown in this study might indicate the necessity of ocular protection to avoid permanent eye damage.