Elastic properties of porcine ocular posterior soft tissues

We examine the thickness and mechanical properties of the porcine posterior retina, choroid, and sclera in different environments and surface directions. Vertical and horizontal samples were surgically obtained. Uniaxial experiments were performed in room-temperature air, room-temperature saline, and body-temperature saline. Sample thicknesses were estimated optically. Thickness of all layers was found to vary significantly among the samples; thickness standard deviation of the mean was 24, 19, and 19% for the retina, choroid, and sclera, respectively. Transition stresses and heel moduli of all layers were consistently higher in saline than air. The retinal stress-strain relationship in air was typically linear with significantly lower horizontal transition strain. Transition stresses and moduli of all layers were consistently lower in body than room temperature and the differences in the transition stresses and heel moduli of the retina and sclera were significant. Also, the sclera had significantly lower transition strains in body temperature. These results illustrate the importance of testing the tissues at conditions like those found in the body. In body-temperature saline, all layers behaved nonlinearly, but only the retina exhibited surface anisotropy between the vertical and horizontal directions.