Dynamic material property measurements of human eyes.

As a result of trauma, approximately 30,000 people become blind in one eye every year in the United States. A common injury prediction tool used for eye injuries is computational modeling, which requires accurate material properties to produce reliable results. The purpose of this study is to determine the dynamic material properties of the human sclera. A high rate pressurization system was used to create a dynamic pressure event to the point of rupture in 5 human eyes. Measurements were obtained for the internal pressure, the diameter of the globe, and the changing coordinates of the optical markers. A relationship between true stress and Green-Lagrangian strain was determined for each test specimen in the x and y direction to show directional effects. It was found that the average maximum true stress was 10.45 +/- 2.28 MPa, the average maximum Green-Lagrangian strain in the x-direction was 0.041 +/- 0.012, and the average maximum Green-Lagrangian strain in the y-direction was 0.073 +/- 0.015. In comparing these data with previous studies, it is concluded that the human eye is both anisotropic and viscoelastic. This study presents dynamic material properties that can be used for establishing injury criteria to help prevent eye injuries in the future.