Abstract
Abstract: :
Purpose: To describe a nonlinear elastic finite element model of the human globe to be used for the prediction of globe rupture. Methods: The globe model consists of nonlinear material properties for the cornea and sclera with globe geometry defined by prior research. Solid components were treated as Lagrangian and fluids as Eulerian. Simulations were performed using LS–DYNA, an explicit code used for dynamic impacts. Validation of the model was performed by measuring eye and model deformation with blunt impacting objects such as soft baseballs and BB’s, at a range of velocities. Thirteen matched tests with eye bank eyes were used for model validation. The energy transfer posteriorly through the corneoscleral shell was investigated, as was energy transfer to the ciliary body, zonules, and lens, for a range of impacts. Results: Globe rupture due to localized deformation occurred at a peak stress in the cornea and sclera of 23 MPa, or peak transient pressure of 2.1 MPa. These results differ significantly from previously obtained peak stresses of 9.4 MPa, from static testing of corneal and scleral strips, and peak pressures of 0.931 MPa. The model also predicted globe rupture due to different mechanisms, i.e., local loading in the case of the BB versus equatorial expansion and rupture due to impact with larger objects. The model accurately predicted globe rupture when validated against 13 matched tests with eye bank eyes for BB energies of 0.59 J (no rupture) and 1.587 J (rupture). The baseball tests performed also show a spectrum of injury from 86.7 J (no rupture) to 124.3 J (rupture). Conclusions: By accurately modeling the geometry of the eye and correctly representing the fluid and solid portions of the eye, it is possible to predict globe rupture trauma due to different injury mechanisms (e.g., local stress due to impingement vs. equatorial expansion), for different types of impacts. This is achieved by using a stress–based criterion rather than energy based one. The model has been empirically validated to be a functional tool for globe rupture prediction. This study sheds light on potential modifications to the model for more detailed trauma prediction, such as hyphema.
Keywords: trauma • motion–3D • sclera