Importance of multiple loading scenarios for the identification of material coefficients of the human cornea

Studer, H; Riedwyl, Hansjörg; Büchler, Philippe

doi:10.1080/10255842.2011.552184

Cited by 11 publications

(8 citation statements)

References 9 publications

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“…Although a comprehensive virtual model of the anterior segment of the eye has not yet been realized, the examples mentioned in the previous paragraphs represent important steps towards the definition of a reliable numerical model of the cornea, although in most cases geometry and material properties were not associated with a particular patient. Interestingly, a few recent contributions have proposed combined experimental and numerical approaches to characterize the individual properties of the cornea [12,13,26,27,[27][28][29], promoting an important advancement towards the construction of patient-specific models. These studies are characterized by the adoption of the state-of-the art computational modelling of soft tissues, and differentiate from other contemporary works based on excessively simplifying assumptions that hinder the predictability of the methods.…”

mentioning

confidence: 99%

Cornea modelling

Pandolfi

2020

Eye and Vis

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Background: Biomechanics introduces numerous technologies to support clinical practice in ophthalmology, with the goal of improving surgical outcomes and to develop new advanced technologies with minimum impact on clinical training. Unfortunately, a few misconceptions on the way that computational methods should be applied to living tissues contributes to a lack of confidence towards computer-based approaches. Methods: Corneal biomechanics relies on sound theories of mechanics, including concepts of equilibrium, geometrical measurements, and complex material behaviors. The peculiarities of biological tissues require the consideration of multi-physics, typical of the eye environment, and to adopt customized geometrical models constructed on the basis of advanced optical imaging and in-vivo testing. Results: Patient-specific models are able to predict the outcomes of refractive surgery and to exploit the results of in-vivo test to characterize the material properties of the corneal tissue. Conclusions: Corneal biomechanics can become an important support to clinical practice, provided that methods are based on the actual multi-physics and use customized geometrical and mechanical models.

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confidence: 99%

Cornea modelling

Pandolfi

2020

Eye and Vis

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“…Preoperative Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany) measurements were taken to create a subject-specific finite element model. The model was numerically simulated using the Optimeyes software (Optimo Medical AG, Biel, Switzerland), employing an earlier published [21,22,23,24,25] constitutive material model. Optimeyes is a comprehensive technology platform for the simulation and prediction of corneal shape and function changes, caused by mechanical interferences with the tissue.…”

Section: Methodsmentioning

confidence: 99%

“…In this work, we used a previously published biomechanical model [21,22,23,24,25] which used additive terms in a non-linear, hyper elastic strain energy function to describe the tissue characteristics. Generally speaking, strain-energy functions are derived from the laws of thermodynamics, and relate deformation (right-hand side of the equation) to deformation energy (left-hand side of the equation).…”

Section: Methodsmentioning

confidence: 99%

Biomechanical Modeling of Pterygium Radiation Surgery: A Retrospective Case Study

Pajic

Aebersold

Eggspuehler

et al. 2017

Sensors

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Pterygium is a vascularized, invasive transformation on the anterior corneal surface that can be treated by Strontium-/Yttrium90 beta irradiation. Finite element modeling was used to analyze the biomechanical effects governing the treatment, and to help understand clinically observed changes in corneal astigmatism. Results suggested that irradiation-induced pulling forces on the anterior corneal surface can cause astigmatism, as well as central corneal flattening. Finite element modeling of corneal biomechanics closely predicted the postoperative corneal surface (astigmatism error −0.01D; central curvature error −0.16D), and can help in understanding beta irradiation treatment. Numerical simulations have the potential to preoperatively predict corneal shape and function changes, and help to improve corneal treatments.

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“…These material coefficients were calibrated using an inverse finite element (FE) approach to exclusively fit experimental inflation test data. Studer et al [7] proceeded to generate two sets of artificial data, consisting of only a single curve for each set, by considering the deformation of a plate along the fibre orientation as well as perpendicular to the fibre orientation. They employed a similar material model definition as the elastic fibre-reinforced model.…”

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confidence: 99%

Calibrating corneal material model parameters using only inflation data: An ill‐posed problem

Kok

Botha

Inglis

2014

Numer Methods Biomed Eng

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SUMMARYGoldmann applanation tonometry (GAT) is a method used to estimate the intraocular pressure by measuring the indentation resistance of the cornea. A popular approach to investigate the sensitivity of GAT results to material and geometry variations is to perform numerical modelling using the finite element method, for which a calibrated material model is required. These material models are typically calibrated using experimental inflation data by solving an inverse problem. In the inverse problem, the underlying material constitutive behaviour is inferred from the measured macroscopic response (chamber pressure versus apical displacement). In this study, a biomechanically motivated elastic fibre-reinforced corneal material model is chosen. The inverse problem of calibrating the corneal material model parameters using only experimental inflation data is demonstrated to be ill-posed, with small variations in the experimental data leading to large differences in the calibrated model parameters. This can result in different groups of researchers, calibrating their material model with the same inflation test data, drawing vastly different conclusions about the effect of material parameters on GAT results. It is further demonstrated that multiple loading scenarios, such as inflation as well as bending, would be required to reliably calibrate such a corneal material model.

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Importance of multiple loading scenarios for the identification of material coefficients of the human cornea

Cited by 11 publications

References 9 publications

Cornea modelling

Cornea modelling

Biomechanical Modeling of Pterygium Radiation Surgery: A Retrospective Case Study

Calibrating corneal material model parameters using only inflation data: An ill‐posed problem

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