Influence of glucocorticosteroids on the biomechanical properties of in-vivo rabbit cornea

Bao, Fangjun; Joda, Akram; Fu, Xun-an; Zhou, Sheng; Wang, Jing; Hu, Xiuli; Wang, Qinmei; Elsheikh, Ahmed

doi:10.1016/j.jmbbm.2013.08.015

Cited by 20 publications

(13 citation statements)

References 31 publications

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“… 37 Corneal biomechanics is depth dependent, and tensile strength in the anterior stroma is nearly twice that of the posterior stroma. 32 To model corneal mechanical behavior, we employed a first-order hyperelastic Ogden material model: 25 , 30 , 38

where

, and

represent the deviatoric principal stretches = J –1/3 λ k ( k = 1, 2, 3); λ 1 , λ 2 , and λ 3 are the principal stretches; J = λ 1 λ 2 λ 3 ; and α , µ , and D are the material constants. D is a compressibility parameter whose value depends on Poisson's ratio ( ν ).…”

Section: Methodsmentioning

confidence: 99%

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Biomechanical Effects of Deep Anterior Lamellar Keratoplasty and Penetrating Keratoplasty for Keratoconus: A Finite Element Analysis

Chen

Zhou

et al. 2021

Trans. Vis. Sci. Tech.

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Purpose To theoretically compare corneal displacement and the von Mises (VM) stress distribution of deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PK) for keratoconus (KC) and to evaluate the effects of residual stromal thickness (RST) and intraocular pressure (IOP) on postoperative corneal biomechanics. Methods We performed DALK and PK simulations using Ansys by employing anisotropic nonlinear hyperelastic corneal material properties. We analyzed corneal displacement and VM stress in DALK and PK models under IOPs of 10, 15, 20, and 25 mmHg. We established two DALK models: The ideal-type DALK ensured that postoperative central corneal thickness was constant at 560 µm and the corneal graft thickness varied with RST. The clinical-type DALK ensured that corneal grafts had the same thickness (500 µm) regardless of RST. Then we analyzed the effects of RST and IOP on postoperative corneal displacement and VM stress. Results Corneal displacement and VM stress were lower in the DALK than in the PK model. In the ideal-type DALK model, an increase in RST was associated with increased deformation and decreased VM stress in the healing zone, except for a RST of 0 µm. In the clinical-type DALK model, deformation and VM stress in the healing zone decreased with an increase in RST, except for a RST of 0 µm. Conclusions DALK showed more stability than PK. For the ideal-type DALK model, an increase in RST resulted in decreased postoperative corneal biomechanics in the healing zone. For the clinical-type DALK model, corneal deformation and VM stress decreased with an increase in RST, which provides numerical evidence for the design of corneal transplantation for patients with KC. Translational Relevance In this computational modeling study, we first theoretically compared corneal biomechanics between DALK and PK for KC. Then, the effects of RST and IOP on postoperative corneal biomechanics were investigated. Our findings provide novel insights into the optimal design for corneal transplantation for patients with KC.

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where

, and

Section: Methodsmentioning

confidence: 99%

“…37 Corneal biomechanics is depth dependent, and tensile strength in the anterior stroma is nearly twice that of the posterior stroma. 32 To model corneal mechanical behavior, we employed a first-order hyperelastic Ogden material model: 25,30,38…”

Section: Corneal Materials Propertiesmentioning

confidence: 99%

Biomechanical Effects of Deep Anterior Lamellar Keratoplasty and Penetrating Keratoplasty for Keratoconus: A Finite Element Analysis

Chen

Zhou

et al. 2021

Trans. Vis. Sci. Tech.

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“…After carrying out measurements using the ORA, the corneas were extracted from the eye globes with a 3-mm ring of scleral tissue and all other ocular components were removed. As described previously [ 25 - 27 ], the corneas were mounted onto a custom designed pressure chamber of an inflation test rig using a mechanical clamp and cyano-acrylate glue to provide watertight connection along their ring of scleral tissue. Care was taken to avoid damage to the epithelium and endothelium.…”

Section: Methodsmentioning

confidence: 99%

High intercorneal symmetry in corneal biomechanical metrics

et al. 2016

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BackgroudTo evaluate the symmetry of corneal biomechanical metrics, measured using an ocular response analyzer (ORA) and self-built corneal inflation test platform, in bilateral rabbit corneas and to investigate their relationship with physical intraocular pressure (IOPp).MethodsTwenty fresh enucleated eyes from ten rabbits were used for ex vivo whole ocular globe inflation. IOP was increased from 7.5 to 37.5 mmHg with 7.5 mmHg steps and biomechanical metrics were acquired using the ORA. At least 3 examinations were performed at each pressure stage. Two biomechanical metrics, corneal hysteresis (CH) and corneal resistance factor (CRF) were recorded and analyzed as a function of IOPp. Corneal specimens were then excised from the intact ocular globe and tested under inflation conditions up to 45.7 mmHg posterior pressure. The experimental pressure-deformation data was analyzed using an inverse modeling procedure to derive the stress-strain behavior of the cornea.ResultsA comparison of corneal shape parameters showed no statistically significant difference (P > 0.05) between bilateral eyes. Similarly, there were no statistically significant differences in values of CH, CRF and corneal stiffness (as measured by the tangent modulus, Et) between bilateral eyes (CH: F = 0.94, P = 0.54; CRF: F = 4.42, P = 0.35; Et: F = 3.15, P = 0.12) at different pressure levels. IOPp was highly correlated with CRF while the relationship with CH was less pronounced.ConclusionsAn obvious interocular symmetry in biomechanical metrics is found in this research. IOP has been shown to have important influences on the value of CRF provided by ORA.

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“…19 A relação entre níveis de glicocorticóides e alteração estruturais da córnea vem sendo pesquisada cada vez mais. 106,135 Existem evidências da diminuição da rigidez de córneas de coelhos que foram tratados com colírios de glicocorticóides. 135 Brown et al 106 demonstraram um aumento significativo da ação lítica de colagenases em córneas de coelhos causado pelo cortisol.…”

Section: Citocinas Inflamatórias Lacrimais No Ceratoconeunclassified

“…106,135 Existem evidências da diminuição da rigidez de córneas de coelhos que foram tratados com colírios de glicocorticóides. 135 Brown et al 106 demonstraram um aumento significativo da ação lítica de colagenases em córneas de coelhos causado pelo cortisol. Há evidência da associaçāo entre níveis elevados de hormônios de estresse em pacientes com apneia, que é uma doença mais prevalente em pacientes com ceratocone.…”

Section: Citocinas Inflamatórias Lacrimais No Ceratoconeunclassified

Correlação entre cortisol capilar, interleucina 6, hormônios tireoideanos e as alterações estruturais dos pacientes com ceratocone em progressão

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superior, sigla derivada da língua inglesa (Inferior-superior Index) IVA Índice de Assimetria Vertical, sigla derivada da língua inglesa (Index of Vertical Assimetry) K Ceratometria, sigla derivada da língua inglesa (Keratometry) KC Ceratocone, sigla derivada da língua inglesa (Keratoconus) K1 Ceratometria Mais Plana, sigla derivada da língua inglesa (Keratometry) K2 Ceratometria Mais Curva, sigla derivada da língua inglesa (Keratometry) Kg Quilograma, sigla derivada da língua inglesa (Kilogram) Km K1 + K2 / 2, Ceratometria Média, sigla derivada da língua inglesa (Keratometry) Kmax Ceratometria Máxima, sigla derivada da língua inglesa (Keratometry) KPI Índice de Predição do ceratocone, sigla derivada da língua inglesa (Keratoconus Prediction Index) Logmar Logaritmo de Ângulo Mínimo de Resolução, sigla derivada da língua inglesa (Logarithm of Minimal Angle of Resolution) LOX Sigla derivada da língua inglesa (Lysyl Oxidase) MEC Matrix Extracellular Min Mínimo Max Máximo MMP Metaloproteinase miRNA Micro RNA Lista de gráficos Gráfico Níveis lacrimais de IL 1B em pacientes com ceratocone comparados ao grupo controle…….……... 58 Gráfico Níveis lacrimais de IL 8 em pacientes com ceratocone comparados ao grupo controle………....... 59 Gráfico Níveis lacrimais de IL 10 em pacientes com ceratocone comparados ao grupo controle…….……... 60 Gráfico Níveis lacrimais de IL12p70 em pacientes com ceratocone comparados ao grupo controle………....… 61 Gráfico Gráfico Níveis lacrimais de TNFα em pacientes com ceratocone comparados ao grupo controle.………...... Níveis lacrimais de IL6 em pacientes com ceratocone comparados ao grupo controle.…………..….……….. 62 63 Gráfico Correlação linear de Pearson entre IL 6 e K2 (A), paquimetria mais fina (B) e epitélio mínimo (C).………………………………….………….………... 65 Gráfico Níveis de cortisol capilar em pacientes com ceratocone comparados ao grupo controle………………………………………………….. 66 Gráfico Correlação linear de Pearson entre cortisol capilar e K2 (A), paquimetria mais fina (B) e epitélio mínimo (C)…………………………………………………………. 67 Gráfico Correlação linear de Pearson entre cortisol capilar e TSH……………………………………………………… 68

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Influence of glucocorticosteroids on the biomechanical properties of in-vivo rabbit cornea

Cited by 20 publications

References 31 publications

Biomechanical Effects of Deep Anterior Lamellar Keratoplasty and Penetrating Keratoplasty for Keratoconus: A Finite Element Analysis

Biomechanical Effects of Deep Anterior Lamellar Keratoplasty and Penetrating Keratoplasty for Keratoconus: A Finite Element Analysis

High intercorneal symmetry in corneal biomechanical metrics

Correlação entre cortisol capilar, interleucina 6, hormônios tireoideanos e as alterações estruturais dos pacientes com ceratocone em progressão

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