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ИСТИНА ЦЭМИ РАН |
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Tonometry, a mechanical test widely used in ophthalmology, is aimed at obtaining information about mechanical characteristics and mechanical state of the eyeball from indirect measurements, i.e., at solving an inverse problem. The model of the eyeball loaded by an external device (tonometer) was developed which contains two important elastic constants. The cornea to which the tonometer is applied is represented by an isotropic, linearly elastic homogenous two-dimensional soft (membrane) shell, which can be mainly characterized by a “corneal stiffness”. The applicability of the membrane approximation is confirmed by experimental data and observations.The sclera with surrounding tissues is modeled by an elastic element which responds to IOP and can be characterized by a single elastic constant (“scleral stiffness”). The dependence of the intraocular volume on IOP and the load applied and the dependence of IOP on the load at a constant volume (tonometry problem) are studied for several tonometer types. The approach developed enables us to find the intraocular pressure and the two elastic constants basing on standard tonometry measurements.