Mechanical eye model for evaluating intraocular pressure measurements

PurposeFor the development of new intraocular pressure (IOP) measurement devices, as well as for comparison with existing devices it is important to consider the various biomechanical properties of the eye in test setups. Therefore, a controllable physical phantom with flexibility in the adjustment of biomechanical parameters and geometries is being proposed and analyzed.MethodsDifferent configurations of a mechanical eye model are simulated together with the applanation process, based on the finite element method (FEM). Forming tools are designed to produce artificial corneas with variable thicknesses and stiffness’s using injection molding. An apparatus is assembled for controlling and evaluating the phantom eye in connection with a piezoelectric IOP test sensor. Measurements are also performed using the commercially available non-contact tonometer NCT-800.ResultsSimulation results for surface pressure and stress distribution at the cornea together with the pressure in the central part of the applanation body show that the pressure reaches a maximum when the local stress is centrally concentrated and decreases to a stable level afterwards. More rigid corneas result in higher maximum values for the pressure. The measurements with the piezoelectric IOP test sensor are in good agreement with the simulation results. The NCT-800 measurements show a significant influence of the biomechanical properties of the cornea on measured IOPs.ConclusionsOur phantom is suitable for describing the effect of biomechanical characteristics of the human eye on tonometric measurements and will facilitate the evaluation of new tonometry systems.