Glaucoma is a common ocular disease that causes irreversible loss of vision. Elevated intraocular pressure (IOP) is the primary risk factor for developing glaucoma. It is believed that increased IOP causes mechanical strain on the glial cells that support the retinal ganglion cell axons and thereby causes ganglion cell apoptosis [1,2]. This damage occurs in the optic nerve head (ONH) region of the eye, and is important for understanding ONH biomechanics. A previous computational sensitivity analysis of factors that might influence ONH biomechanics showed that scleral stiffness had a very large effect on strains in ONH tissues [3]. It is therefore very important to characterize the biomechanical properties of sclera, particularly of peripapillary sclera, the region of the sclera immediately surrounding the ONH The stiffness of human sclera has been previously reported [4, 5], but there have been few biaxial tests of sclera, nor has the anisotropic behavior of the human sclera been investigated in detail. Therefore the goal of this study was to measure the biaxial stress/strain behavior of the human sclera from various locations around the globe in such a way that nonlinearities, inhomogeneities and anisotropies can be quantified.
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