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Two-component model of the eyeball and its application to determining the mechanical characteristics of the eye in clinicsтезисы доклада
- Авторы: Stein A.A., Moiseeva I.N., Lyubimov G.A.
- Сборник: XLII Summer School–Conference “Advanced Problems in Mechanics”, June 30 - July 5, 2014, St. Petersburg (Repino), Russia, APM 2014, Book of Abstracts
- Тезисы
- Год издания: 2014
- Место издания: СОЛО СПб
- Первая страница: 124
- Последняя страница: 125
- Аннотация: 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 standard methods of processing the measurement data are based on physically unjustified models and often yield unreliable results. On the other hand, detailed mechanical models contain numerous mechanical constants which are strongly different for different subjects and cannot be determined in clinics for the eye examined. Therefore, the inverse problem of finding the intraocular pressure (IOP) and the elastic characteristics of the eyeball cannot be solved within such models efficiently. To solve the above-mentioned inverse problem we developed a simple model of the eyeball loaded by an external device (tonometer) 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. This approximation is correct if the tonometer has the shape of a stamp with a sufficiently broad contact area (such as in the Maklakoff tonometer) or a narrow rod used in the Schiøtz tonometer but incorrect for a stamp with a narrow contact area (Goldmann tonometer). 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. Nevertheless, the almost linear form of the IOP-load curves does not allow us to do this efficiently by means of varying the load in a single tonometer. However, the inverse problem can be solved using tonometers of two different types: applanation (flat stamp) and impression (convex stamp or thin rod) tonometers. Moreover, it turned out that for elastic characteristics of the eyeball close to normal the impression tonometry alone yields with practical accuracy the scleral stiffness and IOP. The applanation tonometry can be used for additionally to determine the corneal stiffness.
- Добавил в систему: Моисеева Ирина Никитична