Biomechanical model of the human cornea: Considering shear stiffness and regional variation of collagen anisotropy and density

Whitford, Charles; Studer, H; Boote, Craig; Meek, Keith Michael Andrew; Elsheikh, Ahmed

doi:10.1016/j.jmbbm.2014.11.006

Cited by 82 publications

(85 citation statements)

References 28 publications

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“…These studies have applications as varied as understanding mechanotransduction and fracture in tissues, such as bone [1], tendon [2], cartilage [3], skin [4] and cornea [5]. The structures of such collagen-based extracellular matrices have been studied extensively dating back to the earliest works of Leeuwenhoek [6].…”

Section: Introductionmentioning

confidence: 99%

Tension tests on mammalian collagen fibrils

2016

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A brief overview of isolated collagen fibril mechanics testing is followed by presentation of the first results testing fibrils isolated from load-bearing mammalian tendons using a microelectromechanical systems platform. The in vitro modulus (326 ± 112 MPa) and fracture stress (71 ± 23 MPa) are shown to be lower than previously measured on fibrils extracted from sea cucumber dermis and tested with the same technique. Scanning electron microscope images show the fibrils can fail with a mechanism that involves circumferential rupture, whereas the core of the fibril stays at least partially intact.

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Section: Introductionmentioning

confidence: 99%

Tension tests on mammalian collagen fibrils

2016

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“…One option is the use of PSO optimization scheme for other models (e.g., Holzapfel model, Fung model) not used here. It is common knowledge that the hyperelastic material model is not the only choice to represent the corneal mechanical response, whilst viscoelasticity (Lombardo, Serrao, Rosati, & Lombardo, 2014) and anisotropy (Whitford, Studerb, Booteb, Meekc, & Elsheikh, 2015) should be considered in future research works with PSO. …”

Section: Resultsmentioning

confidence: 99%

<b>Application of particle swarm optimization in inverse finite element modeling to determine the cornea´s mechanical behavior

et al. 2017

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ABSTRACT. Particle Swarm Optimization (PSO) was foregrounded by finite element (FE) modeling to predict the material properties of the human cornea through inverse analysis. Experimental displacements have been obtained for corneas of a donor approximately 50 years old, and loaded by intraocular pressure (IOP). FE inverse analysis based on PSO determined the material parameters of the corneas with reference to first-order, Ogden hyperelastic model. FE analysis was repeated while using the commonly-used commercial optimization software HEEDS, and the rates of the same material parameters were used to validate PSO outcome. In addition, the number of optimization iterations required for PSO and HEEDS were compared to assess the speed of conversion onto a global-optimum solution. Since PSO-based analyses produced similar results with little iteration to HEEDS inverse analyses, PSO capacity in controlling the inverse analysis process to determine the cornea material properties via finite element modeling was demonstrated.Keywords: inverse analysis, finite element method, swarm intelligence, hyperelastic parameters; human corneas.Aplicação da otimização por enxame de partículas na modelagem inversa de elementos finitos para determinar o comportamento mecânico da córnea RESUMO. A otimização por enxame de partículas (PSO) foi usada na modelagem por elementos finitos a fim de se prever as propriedades do material da córnea humana por meio de análise inversa. Deslocamentos experimentais foram obtidos por meio de amostras de córneas provenientes de doadores com aproximadamente 50 anos de idade, as quais sofreram pressão intra-ocular. A análise inversa via Elementos Finitos e baseada no PSO a partir de dados experimentais foi usada para determinar os parâmetros do material de córneas, utilizando como referência o modelo hiperelástico de Ogden de primeira ordem. A análise inversa por Elementos Finitos também foi executada por um programa comercial de otimização e foram encontrados os mesmos valores dos parâmetros do material, o que serviu para validar o resultado do PSO. Além disso, o número de iterações necessárias para a otimização, tanto para o PSO quanto para o programa comercial, foi comparado para avaliar a velocidade de conversão para uma solução global ótima. O estudo mostrou que as análises baseadas no PSO produziram resultados semelhantes com menos iterações para a análise inversa, o que demonstrou o potencial do PSO em controlar o processo de análise inversa para determinar as propriedades mecânicas da córnea por meio de modelagem via Elementos Finitos.Palavras-chave: análise inversa, método dos elementos finitos, inteligência de enxame, parâmetros hiperelásticos, córneas humanas.

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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%

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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Biomechanical model of the human cornea: Considering shear stiffness and regional variation of collagen anisotropy and density

Cited by 82 publications

References 28 publications

Tension tests on mammalian collagen fibrils

Tension tests on mammalian collagen fibrils

<b>Application of particle swarm optimization in inverse finite element modeling to determine the cornea´s mechanical behavior

Biomechanical Modeling of Pterygium Radiation Surgery: A Retrospective Case Study

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