Dynamic material properties of the human sclera

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 is computational modeling, which requires accurate material properties to produce reliable results. Therefore, the purpose of this study was to determine the dynamic material properties of the human sclera. A high-rate pressurization system was used to create dynamic pressure to the point of rupture in 12 human eyes. Measurements were obtained for the internal pressure, the diameter of the globe, the thickness of the sclera, and the changing coordinates of the optical markers using high-rate video, A relationship between true stress and true strain was determined for the sclera tissue in two directions. It was found that the average maximum true stress was 13.89 +/- 4.81 MPa for both the equatorial and meridional directions, the average maximum true strain along the equator was 0.041 +/- 0.014, and the average maximum true strain along the meridian was 0.058 +/- 0.018. Results show a significant difference in the maximum strain in the equatorial and meridional directions (p = 0.02). In comparing these data with previous studies, it is concluded that the human sclera is both anisotropic and viscoelastic. The dynamic material properties presented in this study can be used for advanced models of the human eye to help prevent eye injuries in the future. (C) 2009 Elsevier Ltd. All rights reserved.