Changes and quantitative characterization of hyper-viscoelastic biomechanical properties for young corneal stroma after standard corneal cross-linking treatment with different ultraviolet-A energies

Liu, Taiwei; Shen, Min; Li, Hongxun; Zhang, Yan; Mu, Bokun; Zhao, Xinheng; Wang, Yan

doi:10.1016/j.actbio.2020.06.005

Cited by 18 publications

(7 citation statements)

References 67 publications

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“…In the current study, we found no significant changes in STSC, and corneal elastic modulus (E) after CXL, which may be due to the CXL surgery was carried out in vitro and the corneal elastic modulus was measured under a physiological range of IOP [18]. Liu et al found corneal viscosity decreased significantly after CXL by stress relaxation experiments [24]. While Aabsorbed was also found no significant variations after CXL in this study.…”

Section: Discussioncontrasting

confidence: 42%

Influence of dextran solution and corneal collagen crosslinking on Corneal Biomechanical Parameters Evaluated by Corvis ST

Xiao

Tian

Zhang

et al. 2021

Preprint

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Purpose: To analyze the influence of dextran solution and corneal collagen crosslinking (CXL) on corneal biomechanical parameters evaluated by Corneal Visualization Scheimpflug Technology (Corvis ST). Materials and Methods: Forty porcine eyes were included in this study. Twenty porcine eyes were soaked in dextran solution for 30 minutes (10 eyes in 2% dextran solution and 10 eyes in 20% dextran solution). CXL treatment was performed in 10 porcine eyes, the other 10 porcine eyes were regarded as a control group. Each eye was fixed on an experimental inflation platform to carry out Corvis measurements at different IOPs. Corneal biomechanical parameters were calculated based on Corvis measurement. Statistical analysis was used to analyze the influence of dextran solution and CXL on corneal biomechanical parameters based on Corvis parameters. Results: Corneal energy absorbed area (Aabsorbed) decreased after being soaked in dextran solution under IOP of 15 mmHg; Corneal elastic modulus (E) decreased after being soaked in 2% dextran solution and increased after being soaked in 20% dextran solution; SP-A1 increased after CXL. Conclusion: Both dextran solution and CXL can change corneal biomechanical properties; SP-A1 may be used as an effective parameter for the evaluation of CXL.

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Section: Discussioncontrasting

confidence: 42%

Influence of dextran solution and corneal collagen crosslinking on Corneal Biomechanical Parameters Evaluated by Corvis ST

Xiao

Tian

Zhang

et al. 2021

Preprint

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“…For example, in the uniaxial tensile test of corneal strips, the stress–strain relationship should be

, where

are the initial stress and strain of the specimen, respectively. In many studies, the zero stress state has been taken as the initial state, i.e.,

and

are zero ( Elsheikh et al, 2010 ; Liu et al, 2020a ; Liu et al, 2020b ). According to the Laplace formula, the corneal stress under IOP is

( p , r , and t are the IOP, corneal radius, and corneal thickness, respectively); if the IOP is 16 mmHg, corneal radius and corneal thickness are 6 and 0.57 mm, respectively, the tensile stress of the cornea is 0.0112 MPa under IOP.…”

Section: Discussionmentioning

confidence: 99%

“…According to the determined material parameters in the present study, the corneal tangential modulus is 1.61 ± 0.22 MPa when the strain is 0.01. Elsheikh et al (2010) obtained the tangential modulus of the human cornea which was in the range of 0.32–1.66 MPa by uniaxial tensile test when the strain was about 0.01, and Liu et al (2020b) obtained the elastic modulus of the corneal lenticule from young people which was about 1.2 MPa from the uniaxial tensile test when the strain is within 0.02. The tangential modulus at a strain of 0.01 obtained in this study may be compared with those at a strain of 0.02 or more provided by uniaxial tests.…”

Section: Discussionmentioning

confidence: 99%

Exploring the Biomechanical Properties of the Human Cornea In Vivo Based on Corvis ST

Zhang

Tian

et al. 2021

Front. Bioeng. Biotechnol.

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Purpose: The aim of this study was to provide a method to determine corneal nonlinear viscoelastic properties based on the output data of corneal visualization Scheimpflug technology (Corvis ST).Methods: The Corvis ST data from 18 eyes of 12 healthy humans were collected. Based on the air-puff pressure and the corneal displacement from the Corvis ST test of normal human eyes, the work done by the air-puff attaining the whole corneal displacement was obtained. By applying a visco-hyperelastic strain energy density function of the cornea, in which the first-order Prony relaxation function and the first-order Ogden strain energy were employed, the corneal strain energy during the Corvis ST test was calculated. Then the work done by the air-puff attaining the whole corneal displacement was completely regarded as the strain energy of the cornea. The identification of the nonlinear viscoelastic parameters was carried out by optimizing the sum of difference squares of the work and the strain energy using the genetic algorithm.Results: The visco-hyperelastic model gave a good fit to the data of corneal strain energy with time during the Corvis ST test (R2 > 0.95). The determined Ogden model parameter μ ranged from 0.42 to 0.74 MPa, and α ranged from 32.76 to 55.63. The parameters A and τ in the first-order Prony function were 0.09–0.36 and 1.21–1.95 ms, respectively.Conclusion: It is feasible to determine the corneal nonlinear viscoelastic properties based on the corneal contour information and air-puff pressure of the Corvis ST test.

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“…For instance, crosslinking may significantly increase tensile strength, while not increasing viscosity. 74 Further, different types of crosslinking may modify mechanical properties differently. 75 To understand why, it is necessarily to refer to the hierarchical microstructure of collage in the cornea (see Fig.…”

Section: Measurement Of Biomechanical Change Induced By Crosslinkingmentioning

confidence: 99%

Biomechanics of Ophthalmic Crosslinking

Blackburn

Rollins

Dupps

2021

Trans. Vis. Sci. Tech.

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Crosslinking involves the formation of bonds between polymer chains, such as proteins. In biological tissues, these bonds tend to stiffen the tissue, making it more resistant to mechanical degradation and deformation. In ophthalmology, the crosslinking phenomenon is being increasingly harnessed and explored as a treatment strategy for treating corneal ectasias, keratitis, degenerative myopia, and glaucoma. This review surveys the multitude of exogenous crosslinking strategies reported in the literature, both “light” (involving light energy) and “dark” (involving non-photic chemical processes), and explores their mechanisms, cytotoxicity, and stage of translational development. The spectrum of ophthalmic applications described in the literature is then discussed, with particular attention to proposed therapeutic mechanisms in the cornea and sclera. The mechanical effects of crosslinking are then discussed in the context of their proposed site and scale of action. Biomechanical characterization of the crosslinking effect is needed to more thoroughly address knowledge gaps in this area, and a review of reported methods for biomechanical characterization is presented with an attempt to assess the sensitivity of each method to crosslinking-mediated changes using data from the experimental and clinical literature. Biomechanical measurement methods differ in spatial resolution, mechanical sensitivity, suitability for detecting crosslinking subtypes, and translational readiness and are central to the effort to understand the mechanistic link between crosslinking methods and clinical outcomes of candidate therapies. Data on differences in the biomechanical effect of different crosslinking protocols and their correspondence to clinical outcomes are reviewed, and strategies for leveraging measurement advances predicting clinical outcomes of crosslinking procedures are discussed. Advancing the understanding of ophthalmic crosslinking, its biomechanical underpinnings, and its applications supports the development of next-generation crosslinking procedures that optimize therapeutic effect while reducing complications.

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Changes and quantitative characterization of hyper-viscoelastic biomechanical properties for young corneal stroma after standard corneal cross-linking treatment with different ultraviolet-A energies

Cited by 18 publications

References 67 publications

Influence of dextran solution and corneal collagen crosslinking on Corneal Biomechanical Parameters Evaluated by Corvis ST

Influence of dextran solution and corneal collagen crosslinking on Corneal Biomechanical Parameters Evaluated by Corvis ST

Exploring the Biomechanical Properties of the Human Cornea In Vivo Based on Corvis ST

Biomechanics of Ophthalmic Crosslinking

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