Application of structural analysis to the mechanical behaviour of the cornea

Anderson, Kevin R.; Elsheikh, Ahmed; Newson, Tim

doi:10.1098/rsif.2004.0002

Cited by 171 publications

(136 citation statements)

References 22 publications

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“…16,17 These observations led to a hypothesis on biomechanical pathogenesis of keratoconus based on existing biomechanical models and clinical topographic and tomographic data. 1,18 The hypothesis, later supported by the studies of Scarcelli et al, 2 proposed that the initiating event in keratoconus was a focal reduction in biomechanical properties resulting in tissue thinning as the softer area strains more than the surrounding stiffer areas.…”

Section: Discussionmentioning

confidence: 99%

Detection of Keratoconus With a New Biomechanical Index

Vinciguerra¹,

Ambrósio²,

Elsheikh³

et al. 2016

J Refract Surg

365

294

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he early diagnosis of corneal ectasia is of foremost importance in both screening for refractive surgery and the early treatment of keratoconus. Topography or tomography analysis using either videokeratography or optical coherence tomography instruments can help detect alteration in the shape of the cornea such as thinning and increased curvature. However, these instruments cannot measure the mechanical stability, which is thought to be the initiating event of the disease, even before notable changes in corneal morphology take place.1,2 For this reason, there has been increasing interest in developing instruments to measure the in vivo biomechanical properties of the cornea to aid the diagnosis of an ectasia in a "biomechanical" stage, when topography and tomography are nor-T ABSTRACT PURPOSE: To evaluate the ability of a new combined biomechanical index called the Corvis Biomechanical Index (CBI) based on corneal thickness profile and deformation parameters to separate normal from keratoconic patients.METHODS: Six hundred fifty-eight patients (329 eyes in each database) were included in this multicenter retrospective study. Patients from two clinics located on different continents were selected to test the capability of the CBI to separate healthy and keratoconic eyes in more than one ethnic group using the Corvis ST (Oculus Optikgeräte GmbH, Wetzlar, Germany). Logistic regression was employed to determine, based on Database 1 as the development dataset, the optimal combination of parameters to accurately separate normal from keratoconic eyes. The CBI was subsequently independently validated on Database 2. RESULTS:The CBI included several dynamic corneal response parameters: deformation amplitude ratio at 1 and 2 mm, applanation 1 velocity, standard deviation of deformation amplitude at highest concavity, Ambrósio's Relational Thickness to the horizontal profile, and a novel stiffness parameter. The receiver operating characteristic curve analysis of the training database showed an area under the curve of 0.983. With a cut-off value of 0.5, 98.2% of the cases were correctly classified with 100% specificity and 94.1% sensitivity. In the validation dataset, the same cut-off point correctly classified 98.8% of the cases with 98.4% specificity and 100% sensitivity. CONCLUSIONS:The CBI was shown to be highly sensitive and specific to separate healthy from keratoconic eyes. The presence of an external validation dataset confirms this finding and suggests the possible use of the CBI in everyday clinical practice to aid in the diagnosis of keratoconus.[J Refract Surg. 2016;32(12):803-810.]

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Section: Discussionmentioning

confidence: 99%

Detection of Keratoconus With a New Biomechanical Index

Vinciguerra¹,

Ambrósio²,

Elsheikh³

et al. 2016

J Refract Surg

365

294

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“…While this approach decreases geometrical complexity and increases efficiency of the formulation, it is difficult to extend to complex constitutive models. Anderson et al (23) proposed a corneal model by using shell analysis to develop a nonlinear finite element model to study the mechanical behavior of the cornea. Howland et al (24) , Pinsky and Datye (25) , Li and Tighe (26) , and Elsheikh and Wang (27) also based their models on this method.…”

Section: Modeling Basicsmentioning

confidence: 99%

“…Alastrue et al (5) analyzed the corneal model with the limbus constrained against displacement. Anderson et al (23) compared the deformation pattern of the entire eye model to the rigid cornea-limbus boundary. They proposed an approximate boundary condition, with roller support at the edges inclined at 40° with respect to the horizontal axis, to represent the cornea-limbus behavior.…”

Section: Boundary Conditionsmentioning

confidence: 99%

“…Kohlhaas et al (49) and Wollensak et al (47) extended these tests to study the effects of CXL on the mechanical response of the cornea. Bryant et al (44) , Elsheikh et al (50) , and Anderson et al (23) conducted inflation tests on the entire cornea to determine the apical displacement at different pressure values. Petsche et al (51) examined the depth-dependent material properties of the stroma.…”

Section: Parameter Measurement and Optimizationmentioning

confidence: 99%

“…Researchers in (13) investigated boundary conditions (a), (b), and (c). D) The cornea is allowed to expand along a given surface, as in (11,23,37,38) . Forty degrees from horizontal is taken as a typical angle.…”

Section: Parameter Measurement and Optimizationmentioning

confidence: 99%

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Finite element modelling of cornea mechanics: a review

Nejad

Foster

Gongal

2014

Arquivos Brasileiros De Oftalmologia

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The cornea is a transparent tissue in front of the eye that refracts light and facilitates vision. A slight change in the geometry of the cornea remarkably affects the optical power. Because of this sensitivity, biomechanical study of the cornea can reveal much about its performance and function. In vivo and in vitro studies have been conducted to investigate the mechanics of the cornea and determine its characteristics. Numerical techniques such as the finite element method (FEM) have been extensively implemented as effective and noninvasive methods for analyzing corneal mechanics and possible disorders. This article reviews the use of FEM for assessing the mechanical behavior of the cornea. Different applications of FEM in corneal disease studies, surgical predictions, impact simulations, and clinical applications have been reviewed. Some suggestions for the future of this type of modeling in the area of corneal mechanics are also discussed.

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Computational homogenization of histological microstructures in human prostate tissue: Heterogeneity, anisotropy and tension‐compression asymmetry

Anderson

Ntala

Özel

et al. 2023

Numer Methods Biomed Eng

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Human prostatic tissue exhibits complex mechanical behaviour due to its multiphasic, heterogeneous nature, with hierarchical microstructures involving epithelial compartments, acinar lumens and stromal tissue all interconnected in complex networks. This study aims to establish a computational homogenization framework for quantifying the mechanical behaviour of prostate tissue, considering its multiphasic heterogeneous microstructures and the mechanical characteristics of tissue constituents. Representative tissue microstructure models were reconstructed from high‐resolution histology images. Parametric studies on the mechanical properties of the tissue constituents, particularly the fibre‐reinforced hyper‐elasticity of the stromal tissue, were carried out to investigate their effects on the apparent tissue properties. These were then benchmarked against the experimental data reported in literature. Results showed significant anisotropy, both structural and mechanical, and tension‐compression asymmetry of the apparent behaviours of the prostatic tissue. Strong correlation with the key microstructural indices such as area fractions of tissue constituents and the tissue fabric tensor was also observed. The correlation between the stromal tissue orientation and the principal directions of the apparent properties suggested an essential role of stromal tissue in determining the directions of anisotropy and the compression‐tension asymmetry characteristics in normal human prostatic tissue. This work presented a homogenization and histology‐based computational approach to characterize the apparent mechanical behaviours of human prostatic or other similar glandular tissues, with the ultimate aim of assessing how pathological conditions (e.g., prostate cancer and benign prostatic hyperplasia) could affect the tissue mechanical properties in a future study.

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Application of structural analysis to the mechanical behaviour of the cornea

Cited by 171 publications

References 22 publications

Detection of Keratoconus With a New Biomechanical Index

Detection of Keratoconus With a New Biomechanical Index

Finite element modelling of cornea mechanics: a review

Computational homogenization of histological microstructures in human prostate tissue: Heterogeneity, anisotropy and tension‐compression asymmetry

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