Biaxial Mechanical Behavior of the Choroid and Its Effect on Ocular Trauma Simulations.

Purpose: Ocular trauma can cause blinding conditions such as choroidal rupture (CR) and retinal detachment (RD). The finite element method (FEM) is widely used to evaluate ocular trauma, but the choroid is often oversimplified because of limited mechanical data, potentially reducing simulation accuracy. This study characterized choroidal mechanical properties and incorporated precise viscoelastic data into ocular trauma simulations. Methods: The elastic and viscoelastic properties of the choroid were quantified using biaxial tensile testing. These data were integrated into a finite element model of the human eye incorporating the viscoelastic choroid. BB gun projectile impact simulations were then performed at different speeds to analyze the mechanical responses of posterior ocular tissues. Results: The principal constitutive parameters of the choroid were determined under equibiaxial loading. Simulation results demonstrated that, under identical ocular trauma conditions, inclusion of the choroid altered both scleral and retinal stresses compared with the choroid-excluded eye model, with retinal stress showing a larger change. At an impact speed of 60 m/s, the retinal stress change exceeded 43%. Moreover, the difference in maximum principal stress between the viscoelastic and linear elastic choroid models was 21%, 36%, and 70% at 20, 40, and 60 m/s, respectively. Conclusions: This study provides valuable reference data and a theoretical foundation for understanding the mechanical behavior of the choroid. The proposed computational model underscores the importance of viscoelastic choroid and contributes to improving the accuracy of ocular trauma modeling.