Static and Dynamic Stress/Strain Properties for Human and Porcine Eyes

Every year, more than 2.4 million eye injuries occur in the United States, with over 30,000 of those injured left blind in at least one eye as a result. Computer modeling is one of the most versatile ways to study ocular trauma, however, existing models lack accurate stress and strain properties for ocular globe rupture. A pressure system was built to examine static and dynamic globe rupture pressures for healthy postmortem human and porcine (pig) eyes. Maximum rupture stress for the quasi-static tests was found to be 11.17MPa for human tissue and 12.08MPa for porcine tissue, whereas stress for the dynamic tests was found to be 30.18MPa for human tissue and 26.01MPa for porcine tissue. Maximum rupture stress results correlate well with static material properties used in published research (9.4MPa), and dynamic properties of 23MPa found in published research. Healthy postmortem human eyes were ruptured statically and dynamically to determine the relationship between stress and strain for the ocular globe under intraocular pressure loading. Stress-strain relationships were investigated and values for the elastic modulus were found to be slightly lower than that previously published. This research shows that it is important to differentiate between tissue type, and static versus dynamic failure properties before drawing conclusions from computer models and other published research. Now that rupture can be accurately determined, safety systems designed to protect eyesight in automotive, sports, and military applications can also be applied to protect the quality of life for humans in these applications.