A multiphase approach is presented to investigate biomechanical response of soft hydrated tissues. An updated lagrangian formulation has been developed to take into account geometric and material non-linearities in the coupled problem of a fluid which flows in a solid matrix which undergoes large deformations. A hypoelastic constitutive law is defined for the solid matrix as a function of the objective eulerian strain rate and the associated objective stress rate measure defined by Jaumann. Several non-linear permeability laws have been studied to evaluate the effects of variations in the drainage system of the human eye that can lead to diseases as ocular hypertension or glaucoma. The formulation, discretized by a Newmark’s scheme and linearised by a Newton-Raphson procedure, has been implemented in a Finite Element Code. Trabecular meshwork (TM), Schlemm’s canal, ciliary muscle and uveoscleral pathway regulate the aqueous outflow in order to maintain a steady intraocular pressure. In particular, trabecular meshwork has the main rule in the regulation of the aqueous humour to avoid its accumulation in the anterior chamber. A TM axial-simmetrical model has been analysed with different initial conditions: if constant aqueous outflow is assumed, our results show that variation in TM permeability determines a final variation of internal ocular pressure (IOP) significantly larger than expected by a linear analysis. In fact, when permeability decreases in TM, pressure increases and induces a compression in the tissue that affects its permeability distribution and thus determines a further rise in IOP.

A Computational Formulation for Coupled Response of Trabecular Meshwork in Human Eye

MEROI, EMILIO;
2005-01-01

Abstract

A multiphase approach is presented to investigate biomechanical response of soft hydrated tissues. An updated lagrangian formulation has been developed to take into account geometric and material non-linearities in the coupled problem of a fluid which flows in a solid matrix which undergoes large deformations. A hypoelastic constitutive law is defined for the solid matrix as a function of the objective eulerian strain rate and the associated objective stress rate measure defined by Jaumann. Several non-linear permeability laws have been studied to evaluate the effects of variations in the drainage system of the human eye that can lead to diseases as ocular hypertension or glaucoma. The formulation, discretized by a Newmark’s scheme and linearised by a Newton-Raphson procedure, has been implemented in a Finite Element Code. Trabecular meshwork (TM), Schlemm’s canal, ciliary muscle and uveoscleral pathway regulate the aqueous outflow in order to maintain a steady intraocular pressure. In particular, trabecular meshwork has the main rule in the regulation of the aqueous humour to avoid its accumulation in the anterior chamber. A TM axial-simmetrical model has been analysed with different initial conditions: if constant aqueous outflow is assumed, our results show that variation in TM permeability determines a final variation of internal ocular pressure (IOP) significantly larger than expected by a linear analysis. In fact, when permeability decreases in TM, pressure increases and induces a compression in the tissue that affects its permeability distribution and thus determines a further rise in IOP.
2005
9788495999719
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11578/4327
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