Influence of analytical methods versus clamping procedure on biomechanical response of cornea through experimental strip tests

The geometric and material parameters are seen to directly affect the biomechanical response of cornea, for example in tonometry they are responsible for possible errors in pressure readings (referred to as Goldman IOP or IOPG). Some of the critical geometric parameters include radius, curvature, asphericity and, central and peripheral thicknesses that vary with ethnic origin of specimen. While the material parameters, such as stiffness, viscosity hyper elasticity and anisotropy largely depend on age, genetics and environmental exposure. Therefore, to understand the response of such parameters, experimental strip tests are normally used to characterise the problem. While other studies have identified the response and significance of geometrical parameters on IOP, the current study evaluates the impact of key assumptions made during optimisation through mathematical models. In addition, the assumptions are implemented on a set of experimental data (coupon tests on an Instron machine over expensive inflation test procedures) to obtain stress–strain response of corneal specimens. In addition to outlining the shortcomings in current experimental procedures and theoretical assumptions, possible conclusions are also made to improve the accuracy of the outcome of results: for example, an anisotropic behaviour is significantly reduced or diminished with further improvement in geometrical assumptions and careful clamping procedures. As a result, contrary to current assumptions in literature, it may be argued that the cornea has anisotropy along superior–inferior (vertical) and temporal–nasal (horizontal) directions.