Anisotropic and inhomogeneous mechanical characteristics of the retina

We studied contribution of blood vessels to the mechanical properties of retina. Previous studies revealed anisotropic and inhomogeneous retinal mechanical characteristics. To examine different vessel types and sizes, 3 strips of retinal samples were dissected in each of 5 pig eyes. One strip contained the superior-temporal vein in the axial direction, one strip contained the superior-temporal artery in the axial direction, and one strip did not contain any visible vessel. To examine different vessel orientations, 2 strips of retinal samples were dissected in each of 5 other pig eyes. One strip contained the superior-temporal vein in the axial direction, and one strip contained the superior-temporal vein in the circumferential direction. Tensile testing was performed on the samples. The venous and arterial samples were found to be significantly stiffer than the no-visible-vessel samples. No significant difference was observed neither between the venous and arterial samples, nor between the venous samples in the axial versus circumferential directions. We therefore conclude that the blood vessels contribute significantly to the stiffness of the retina, and the vessel size is the only determining factor that governs the anisotropic and inhomogeneous characteristics of the retina.