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Hatami-Marbini H, Emu ME. The role of KS GAGs in the microstructure of CXL-treated corneal stroma; a transmission electron microscopy study. Exp Eye Res 2023; 231:109476. [PMID: 37068601 PMCID: PMC10826592 DOI: 10.1016/j.exer.2023.109476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Revised: 01/30/2023] [Accepted: 04/14/2023] [Indexed: 04/19/2023]
Abstract
The mechanical and physical properties of the cornea originate from the microstructure and composition of its extracellular matrix. It is known that collagen fibrils, with a relatively uniform diameter, are organized in a pseudo-hexagonal array. It has been suggested that proteoglycans and the interaction of their glycosaminoglycan (GAG) side chains with themselves and collagen fibrils are important for collagen fibril organization inside the cornea. There are several diseases such as keratoconus in which the regular collagen fibrillar packing becomes distorted causing corneal optical and mechanical properties to be compromised. The primary purpose of the present work was to investigate the role of GAGs on the microstructure of corneal extracellular matrix before and after corneal crosslinking (CXL) treatment. For this purpose, keratan sulphates (KS) were removed from corneal samples using the keratanase enzyme and the CXL procedure was used to crosslink the specimens. The transmission electron microscopy was then used to characterize the diameter of collagen fibrils and their interfibrillar spacing. It was found that KS GAG depletion increased the collagen interfibrillar spacing while the CXL treatment significantly decreased the interfibrillar spacing. The enzyme and CXL treatments had an insignificant effect on the diameter of collagen fibrils. The underlying mechanisms responsible for these observations were discussed in terms of the assumption that GAG chains form duplexes that behave as tiny ropes holding collagen fibrils in place.
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Affiliation(s)
- H Hatami-Marbini
- Mechanical and Industrial Engineering Department, University of Illinois at Chicago, Chicago, IL, USA.
| | - M E Emu
- Mechanical and Industrial Engineering Department, University of Illinois at Chicago, Chicago, IL, USA
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Hatami-Marbini H, Emu ME. Effect of corneal collagen crosslinking on viscoelastic shear properties of the cornea. J Mech Behav Biomed Mater 2022; 133:105300. [PMID: 35749931 PMCID: PMC10826593 DOI: 10.1016/j.jmbbm.2022.105300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 04/08/2022] [Accepted: 05/27/2022] [Indexed: 11/26/2022]
Abstract
The cornea is responsible for most of the refractive power in the eye and acts as a protective layer for internal contents of the eye. The cornea requires mechanical strength for maintaining its precise shape and for withstanding external and internal forces. Corneal collagen crosslinking (CXL) is a treatment option to improve corneal mechanical properties. The primary objective of this study was to characterize CXL effects on viscoelastic shear properties of the porcine cornea as a function of compressive strain. For this purpose, corneal buttons were prepared and divided into three groups: control group (n = 5), pseudo-crosslinked group (n = 5), and crosslinked group (n = 5). A rheometer was used to perform dynamics torsional shear experiments on corneal disks at different levels of compressive strain (0%-40%). Specifically, strain sweep experiments and frequency sweep tests were done in order to determine the range of linear viscoelasticity and frequency dependent shear properties, respectively. It was found that the shear properties of all samples were dependent on the shear strain magnitude, loading frequency, and compressive strain. With increasing the applied shear strain, all samples showed a nonlinear viscoelastic response. Furthermore, the shear modulus of samples increased with increasing the frequency of the applied shear strain and/or increasing the compressive strain. Finally, the CXL treatment significantly increased the shear storage and loss moduli when the compressive strain was varied from 0% to 30% (p < 0.05); larger shear moduli were observed at compressive 40% strain but the difference was not significant (P = 0.12).
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Affiliation(s)
- Hamed Hatami-Marbini
- Mechanical and Industrial Engineering Department, University of Illinois at Chicago, Chicago, IL, USA.
| | - Md Esharuzzaman Emu
- Mechanical and Industrial Engineering Department, University of Illinois at Chicago, Chicago, IL, USA
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Wang L, Wang J, Sun H, Pang Z, Mu G. Corneal Collagen Cross-Linking Inhibits Corneal Blood and Lymphatic Vessels Temporarily in Alkali-Burned Rabbits. Curr Eye Res 2022; 47:1266-1271. [PMID: 35634710 DOI: 10.1080/02713683.2022.2079143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
PURPOSE This study aimed to explore whether corneal cross-linking (CXL) could regress corneal blood vessels (CBV) and corneal lymphatic vessels (CLV) in alkali-burned rabbits. METHODS A total of 80 rabbits 2-3 months old weighing 1.5-2.0 kg were randomly divided into four groups: CXL7 group; CTL7 group; CXL14 group; and CTL14 group. Then, 3% sodium pentobarbital 1 ml/kg and tetracaine eye drop 5 g/L were administered before surgery. NaOH 2 mol/L was topically applied to the central cornea to establish the alkali burning model. Then CXL was administered within 2 h in groups CXL7 and CXL14. Corneal opacity and edema, CBV and CLV volume, cluster differentiation 31 (CD31), and lymphatic vessel endothelial receptor 1 (LYVE-1) expression levels were analyzed on days 7 and 14. RESULTS CXL reduced cornea opacity, CNV, and CLV volumes on day 7 in alkali-burned rabbits. However, CNV and CLV volumes were increased on day 14. CXL also showed down- and upregulation of CD31 and LYVE-1 expression levels on days 7 and 14, respectively. CONCLUSIONS CXL effectively regulated CBV and CLV in alkali-burned rabbits. The transient angioregression and lymphangioregression induced by CXL may be potentially helpful in vascularized high-risk eyes.
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Affiliation(s)
- Lijun Wang
- Department of Ophthalmology, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, Shandong, China.,Department of Ophthalmology, Binzhou Medical University Hospital, Binzhou, Shandong, China
| | - Jia Wang
- Department of Ophthalmology, Aier Eye Hospital Group (J.W.), LiaochengAier Eye Hospital, Liaocheng, Shandong, China
| | - Hongkun Sun
- Department of Hematopathology, Binzhou Medical University Hospital, Binzhou, Shandong, China
| | - Zuoxiang Pang
- Department of Ophthalmology, Weifang Eye Hospital, Weifang, Shandong, China
| | - Guoying Mu
- Department of Ophthalmology, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, Shandong, China
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Tian L, Qin X, Zhang H, Zhang D, Guo LL, Zhang HX, Wu Y, Jie Y, Li L. A Potential Screening Index of Corneal Biomechanics in Healthy Subjects, Forme Fruste Keratoconus Patients and Clinical Keratoconus Patients. Front Bioeng Biotechnol 2022; 9:766605. [PMID: 35004638 PMCID: PMC8733640 DOI: 10.3389/fbioe.2021.766605] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2021] [Accepted: 11/08/2021] [Indexed: 12/27/2022] Open
Abstract
Purpose: This study aims to evaluate the validity of corneal elastic modulus (E) calculated from corneal visualization Scheimpflug technology (Corvis ST) in diagnosing keratoconus (KC) and forme fruste keratoconus (FFKC). Methods: Fifty KC patients (50 eyes), 36 FFKC patients (36 eyes, the eyes were without morphological abnormality, while the contralateral eye was diagnosed as clinical keratoconus), and 50 healthy patients (50 eyes) were enrolled and underwent Corvis measurements. We calculated E according to the relation between airpuff force and corneal apical displacement. One-way analysis of variance (ANOVA) and receiver operating characteristic (ROC) curve analysis were used to identify the predictive accuracy of the E and other dynamic corneal response (DCR) parameters. Besides, we used backpropagation (BP) neural network to establish the keratoconus diagnosis model. Results: 1) There was significant difference between KC and healthy subjects in the following DCR parameters: the first/second applanation time (A1T/A2T), velocity at first/second applanation (A1V/A2V), the highest concavity time (HCT), peak distance (PD), deformation amplitude (DA), Ambrosio relational thickness to the horizontal profile (ARTh). 2) A1T and E were smaller in FFKC and KC compared with healthy subjects. 3) ROC analysis showed that E (AUC = 0.746) was more accurate than other DCR parameters in detecting FFKC (AUC of these DCR parameters was not more than 0.719). 4) Keratoconus diagnosis model by BP neural network showed a more accurate diagnostic efficiency of 92.5%. The ROC analysis showed that the predicted value (AUC = 0.877) of BP neural network model was more sensitive in the detection FFKC than the Corvis built-in parameters CBI (AUC = 0.610, p = 0.041) and TBI (AUC = 0.659, p = 0.034). Conclusion: Corneal elastic modulus was found to have improved predictability in detecting FFKC patients from healthy subjects and may be used as an additional parameter for the diagnosis of keratoconus.
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Affiliation(s)
- Lei Tian
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University and Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, China.,Beijing Advanced Innovation Center for Big Data-Based Precision Medicine, Beijing Tongren Hospital, Beihang University & Capital Medical University, Beijing, China
| | - Xiao Qin
- Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing, China.,School of Biomedical Engineering, Capital Medical University, Beijing, China.,Department of Ophthalmology, Chinese People's Liberation Army General Hospital, Beijing, China
| | - Hui Zhang
- Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing, China.,School of Biomedical Engineering, Capital Medical University, Beijing, China
| | - Di Zhang
- Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing, China.,School of Biomedical Engineering, Capital Medical University, Beijing, China
| | - Li-Li Guo
- The First People's Hospital of Xuzhou, Xuzhou, China
| | - Hai-Xia Zhang
- Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing, China.,School of Biomedical Engineering, Capital Medical University, Beijing, China
| | - Ying Wu
- Department of Ophthalmology, Chinese People's Liberation Army General Hospital, Beijing, China
| | - Ying Jie
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University and Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, China
| | - Lin Li
- Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing, China.,School of Biomedical Engineering, Capital Medical University, Beijing, China
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Dry vs. wet: Properties and performance of collagen films. Part II. Cyclic and time-dependent behaviours. J Mech Behav Biomed Mater 2020; 112:104040. [DOI: 10.1016/j.jmbbm.2020.104040] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 08/08/2020] [Accepted: 08/12/2020] [Indexed: 12/21/2022]
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Alania Y, Reis MCD, Nam JW, Phansalkar RS, McAlpine J, Chen SN, Pauli GF, Bedran-Russo AK. A dynamic mechanical method to assess bulk viscoelastic behavior of the dentin extracellular matrix. Dent Mater 2020; 36:1536-1543. [PMID: 33129510 DOI: 10.1016/j.dental.2020.09.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 07/07/2020] [Accepted: 09/10/2020] [Indexed: 11/29/2022]
Abstract
OBJECTIVES To develop a protocol for assessment of the bulk viscoelastic behavior of dentin extracellular matrix (ECM), and to assess relationships between induced collagen cross-linking and viscoelasticity of the dentin ECM. METHODS Dentin ECM was treated with agents to induce exogenous collagen cross-linking: proanthocyanidins (PACs) from Vitis vinifera - VVe, PACs from Pinus massoniana - PMe, glutaraldehyde - (GA), or kept untreated (control). A dynamic mechanical strain sweep method was carried out in a 3-point bending submersion clamp at treatment; after protein destabilization with 4 M urea and after 7-day, 6-month, and 12-month incubation in simulated body fluid. Tan δ, storage (E'), loss (E"), and complex moduli (E*) were calculated and data were statistically analyzed using two-way ANOVA and post-hoc tests (α = 0.05). Chemical analysis of dentin ECM before and after protein destabilization was assessed with ATR-FTIR spectroscopy. RESULTS Significant interactions between study factors (treatment vs. time points, p < 0.001) were found for all viscoelastic parameters. Despite a significant decrease in all moduli after destabilization, PAC-treated dentin remained statistically higher than control (p < 0.001), indicating permanent mechanical enhancement after biomodification. Covalently crosslinked, GA-treated dentin was unaffected by destabilization (p = 0.873) and showed the lowest damping capacity (tan δ) at all time points (p < 0.001). After 12 months, the damping capacity of PMe and VVe groups decreased significantly. Changes in all amide IR resonances revealed a partial chemical reversal of PAC-mediated biomodification. SIGNIFICANCE Viscoelastic measurements and IR spectroscopy aid in elucidating the role of inter-molecular collagen cross-linking in the mechanical behavior of dentin ECM.
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Affiliation(s)
- Yvette Alania
- Department of Restorative Dentistry, College of Dentistry, University of Illinois at Chicago, Chicago, IL 60612, USA; Department of General Dental Sciences, School of Dentistry, Marquette University, Milwaukee, WI 53233, USA
| | - Mariana Cavalcante Dos Reis
- Department of Restorative Dentistry, College of Dentistry, University of Illinois at Chicago, Chicago, IL 60612, USA; Department of General Dental Sciences, School of Dentistry, Marquette University, Milwaukee, WI 53233, USA
| | - Joo-Won Nam
- Department of Pharmaceutical Sciences and Pharmacognosy Institute, College of Pharmacy, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Rasika S Phansalkar
- Department of Pharmaceutical Sciences and Pharmacognosy Institute, College of Pharmacy, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - James McAlpine
- Department of Pharmaceutical Sciences and Pharmacognosy Institute, College of Pharmacy, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Shao-Nong Chen
- Department of Pharmaceutical Sciences and Pharmacognosy Institute, College of Pharmacy, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Guido F Pauli
- Department of Pharmaceutical Sciences and Pharmacognosy Institute, College of Pharmacy, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Ana K Bedran-Russo
- Department of Restorative Dentistry, College of Dentistry, University of Illinois at Chicago, Chicago, IL 60612, USA; Department of General Dental Sciences, School of Dentistry, Marquette University, Milwaukee, WI 53233, USA.
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The Mechanical Interpretation of Ocular Response Analyzer Parameters. BIOMED RESEARCH INTERNATIONAL 2019; 2019:5701236. [PMID: 31380431 PMCID: PMC6662474 DOI: 10.1155/2019/5701236] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 06/03/2019] [Accepted: 06/20/2019] [Indexed: 11/17/2022]
Abstract
Purpose Ocular Response Analyzer (ORA) is one of the most widely used devices in clinic, while the mechanical interpretations of parameters obtained from ORA have not been understood completely. The aim of this research is to explore the mechanical interpretation of ORA parameters. Methods Rabbits aged 3-24 months were measured with ORA in vivo and corneal strips uniaxial tensile tests to get ORA parameters and corneal biomechanical parameters (corneal elastic modulus, relaxation time, and relaxation limit). The mechanical interpretation of ORA parameters was cognized preliminarily by analyzing the correlation between ORA parameters and corneal biomechanical parameters. On the other hand, finite element method was applied to simulate ORA measurements with different corneal biomechanical parameters to obtain quantitative relationship between ORA parameters and corneal biomechanical parameters further. Results Biomechanical experimental results showed that Corneal Resistance Factor (CRF) was correlated with corneal elastic modulus and relaxation limit significantly, while the significant correlations between Corneal Hysteresis (CH) and corneal biomechanical parameters were not observed. Results of finite element analysis showed that both CH and CRF were correlated with corneal elastic modulus, relaxation limit, and relaxation time significantly. Besides, corneal elastic modulus was positively correlated with upslop1 and upslop2 and negatively correlated with w2. Conclusions For all ORA parameters, CH, CRF, the upslope, and the width of the peaks are parameters which may reflect corneal elastic properties. It is viable to cognize mechanical interpretation of ORA parameters by the comparisons of the data from ORA and biomechanical tests of rabbits with different ages and the simulations of ORA based on finite element methods. Further studies are needed to confirm the mechanical interpretation.
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Tan X, Agrawal A, Hammer DX, Ilev I. Application of optical coherence tomography and optical path length method for monitoring corneal thickness and refractive index change during corneal cross-linking. APPLIED OPTICS 2019; 58:4616-4621. [PMID: 31251279 DOI: 10.1364/ao.58.004616] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 05/08/2019] [Indexed: 06/09/2023]
Abstract
Corneal cross-linking (CXL) using UVA irradiation with a riboflavin photosensitizer has emerged as a new treatment paradigm for corneal ectatic disorders. The thickness threshold for protection of intraocular structures has often been challenged with ongoing developments, and corneal thinning becomes an important safety concern, especially for patients with thin corneas. In this study with an ex vivo bovine eye model, we monitored corneal thinning and corneal refractive index changes using optical coherence tomography (OCT) integrated with an adaptation of the optical path length method. CXL experiments were performed based on the standard protocol that includes removal of the corneal epithelium to facilitate diffusion of riboflavin into the stroma. The corneal stromal thickness and group refractive index were measured by a 1310 nm Fourier-domain OCT imaging system at three critical points of the procedure: immediately after epithelial removal, after 30 min riboflavin instillation, and after 30 min UVA irradiation with continuing instillation. We found that the refractive index of the bovine cornea changed significantly from epithelial removal to riboflavin instillation and UVA irradiation, increasing from 1.377±0.005 (mean±standard deviation) after de-epithelization to 1.387±0.003 after 30 min instillation and 1.388±0.008 after subsequent irradiation. The corneas also underwent a considerable decrease (10%-20%) in stromal thickness with thinning of 95±29 μm (mean±standard deviation) after riboflavin instillation and a further decrease (∼5%) with thinning of 42±19 μm after UVA irradiation. Our study highlights the importance of corneal thickness monitoring during CXL, especially after riboflavin instillation when the decrease is the largest, to avoid delivering endothelial cytotoxic doses. An increase in refractive index heightens the concern for corneal thinning and the need for careful monitoring as a safety precaution.
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Schröder S, Eppig T, Liu W, Schrecker J, Langenbucher A. Keratoconic eyes with stable corneal tomography could benefit more from custom intraocular lens design than normal eyes. Sci Rep 2019; 9:3479. [PMID: 30837552 PMCID: PMC6401116 DOI: 10.1038/s41598-019-39904-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Accepted: 01/31/2019] [Indexed: 12/18/2022] Open
Abstract
We investigated whether eyes with keratoconic corneal tomography pattern could benefit more from aberration correction with custom intraocular lenses (IOLs) than normal cataractous eyes despite the effect of misalignment on the correction of aberrations. Custom IOLs (cIOLs) were calculated for twelve normal and twelve keratoconic eyes using personalized numerical ray tracing models. The Stiles-Crawford weighted root-mean-square spot-size (wRMS) at the virtual fovea was evaluated for cIOLs and aberration-neutral IOLs (nIOLs) in a simulated clinical study with 500 virtual IOL implantations per eye and per IOL. IOL misalignment (decentration, tilt, rotation) and pupillary ectopia (4.5 mm iris aperture) were varied upon each virtual implantation. The nIOLs achieved average wRMS of 16.4 ± 4.3 μm for normal, and 92.7 ± 34.4 μm for keratoconic eyes (mean ± standard deviation). The cIOLs reduced the average wRMS to 10.3 ± 5.8 μm for normal, and 28.5 ± 18.6 μm for keratoconic eyes. The cIOLs produced smaller wRMS than nIOLs in most virtual implantations (86.7% for normal and 99.4% for keratoconic eyes). IOL misalignment resulted in larger wRMS variations in the keratoconus group than in the normal group. Custom freeform IOL-optics-design may become a promising option for the correction of advanced aberrations in eyes with non-progressive keratoconic corneal tomography pattern.
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Affiliation(s)
- Simon Schröder
- Saarland University, Institute of Experimental Ophthalmology, Kirrberger Str. 100, Bldg. 22, D-66424, Homburg/Saar, Germany.
| | - Timo Eppig
- Saarland University, Institute of Experimental Ophthalmology, Kirrberger Str. 100, Bldg. 22, D-66424, Homburg/Saar, Germany
| | - Weidi Liu
- Saarland University, Institute of Experimental Ophthalmology, Kirrberger Str. 100, Bldg. 22, D-66424, Homburg/Saar, Germany
- University of Rochester, Institute of Optics, 275 Hutchison Road, Rochester, NY, 1427-0186, USA
- Rice University, 301 Space Science, 6100 Main, St Houston, TX, 77005, USA
| | - Jens Schrecker
- Rudolf-Virchow-Klinikum Glauchau, Department of Ophthalmology, Virchowstr. 18, D-08371, Glauchau, Germany
| | - Achim Langenbucher
- Saarland University, Institute of Experimental Ophthalmology, Kirrberger Str. 100, Bldg. 22, D-66424, Homburg/Saar, Germany
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Decellularisation affects the strain rate dependent and dynamic mechanical properties of a xenogeneic tendon intended for anterior cruciate ligament replacement. J Mech Behav Biomed Mater 2019; 91:18-23. [DOI: 10.1016/j.jmbbm.2018.11.023] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Revised: 11/02/2018] [Accepted: 11/23/2018] [Indexed: 01/20/2023]
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Sedaghat MR, Momeni-Moghaddam H, Ambrósio R, Roberts CJ, Yekta AA, Danesh Z, Reisdorf S, Khabazkhoob M, Heidari HR, Sadeghi J. Long-term Evaluation of Corneal Biomechanical Properties After Corneal Cross-linking for Keratoconus: A 4-Year Longitudinal Study. J Refract Surg 2019; 34:849-856. [PMID: 30540368 DOI: 10.3928/1081597x-20181012-02] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Accepted: 10/10/2018] [Indexed: 11/20/2022]
Abstract
PURPOSE To compare the long-term changes in corneal biomechanics, topography, and tomography before and 4 years after corneal cross-linking (CXL) with the Dresden protocol and correlate these changes with visual acuity. METHODS In this longitudinal study, 18 eyes of 18 patients with progressive keratoconus who were treated with CXL were included. All patients received a standard ophthalmological examination and were examined by Placido disc-based topography, Scheimpflug tomography, and biomechanical assessments with the Corvis ST (OCULUS Optikgeräte GmbH, Wetzlar, Germany) and Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments, Buffalo, NY) before and 4 years after CXL. The main outcome measures were dynamic corneal response (DCR) parameters obtained from the Corvis ST, corneal hysteresis (CH), corneal resistance factor (CRF), visual acuity, refraction, corneal curvature, and corneal thickness. RESULTS There were no significant differences in mean visual acuity, refraction, intraocular pressure, corneal topography, corneal astigmatism in both corneal surfaces, maximum keratometry, corneal thickness at apical and thinnest points, thickness profile indices, corneal volume, and specular microscopy before and 4 years after CXL (P > .05). Significant changes were observed in many DCR parameters, including radius at highest concavity and integrated inverse radius, both of which were consistent with stiffening. The CH and CRF values after CXL were not statistically significant. The new parameters using the Corvis ST include integrated inverse concave radius, which showed a significant decrease 1.07 ± 0.93 mm-1, consistent with stiffening. The corneal stiffness parameter at the first applanation, Ambrósio's Relational Thickness to the horizontal profile, deformation amplitude ratio, and Corvis Biomechanical Index as a combined biomechanical screening parameter did not show significant changes. CONCLUSIONS CXL is a minimally invasive treatment option to prevent keratoconus progression over 4 years. Pressure-derived biomechanical parameters obtained from the ORA did not show any change following CXL at 4 years of follow-up, whereas the Corvis ST DCR parameters detected changes in corneal biomechanical properties. [J Refract Surg. 2018;34(12):849-856.].
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Effect of Collagen Cross-Linking on Alkali Burn-Induced Corneal Neovascularization in Rabbits. J Ophthalmol 2018; 2018:7325483. [PMID: 30402279 PMCID: PMC6198613 DOI: 10.1155/2018/7325483] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 09/13/2018] [Indexed: 11/18/2022] Open
Abstract
Objective This study aims at investigating the effects and molecular mechanism of riboflavin-ultraviolet-A-induced cross-linking (corneal collagen cross-linking, CXL) on corneal neovascularization (CNV) in a rabbit alkali burn model. Methods A total of 60 rabbits were injured with alkali burns to induce CNV in the right eye and were randomly divided into six groups: Group A-injury and no treatment; Groups B, C, and D-CXL treatment for 30 min, 15 min, and 45 min administered immediately after injury, respectively; and Groups E and F-CXL treatment for 30 min administered 1 day and 3 days after injury, respectively. CNV area, corneal edema, and corneal epithelial defects were observed on days 4, 7, 10, and 14 after injury. Western blot was used to detect expression of the vascular endothelial growth factor (VEGF), matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-2 (MMP-9), and tissue inhibitor of metalloproteinases 1 (TIMP-1) at 7 and 14 days after injury. Results CXL treatment decreased CNV and corneal edema in all groups compared to Group A. On day 7, MMP-9 expression was significantly increased in all CXL treatment groups, and TIMP-1 was upregulated in Groups D and F compared to Group A. In addition, VEGF, MMP-2, MMP-9, and TIMP-1 expression were increased in Group A on day 14 after injury. Conclusions Our results indicate that riboflavin-ultraviolet-A-induced cross-linking (corneal collagen cross-linking, CXL) significantly inhibits alkali burn-induced CNV in rabbits, possibly through downregulating VEGF, MMP-2, MMP-9, and TIMP-1 expression.
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Hatami-Marbini H. Influence of Microstructure on Stiffening Effects of Corneal Cross-linking Treatment. J Refract Surg 2018; 34:622-627. [DOI: 10.3928/1081597x-20180718-01] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Accepted: 07/09/2018] [Indexed: 11/20/2022]
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Relationship between initial corneal hydration and stiffening effects of corneal crosslinking treatment. J Cataract Refract Surg 2018; 44:756-764. [PMID: 30041742 DOI: 10.1016/j.jcrs.2018.01.036] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 11/18/2017] [Accepted: 01/17/2018] [Indexed: 11/21/2022]
Abstract
PURPOSE To characterize the mechanical property improvement of riboflavin and ultraviolet light corneal crosslinking (CXL) procedure in artificially swollen human and porcine corneas. SETTING Computational Biomechanics Research Laboratory, Mechanical and Industrial Engineering Department, University of Illinois at Chicago, Illinois, USA. DESIGN Experimental study. METHODS Porcine and human donor corneas were crosslinked at different hydration levels using riboflavin-dextran solutions of different osmolality. Four porcine groups (Hw [hydration in mg H2O/mg dry tissue] = 3.3 ± 0.2 [SD]; 4.0 ± 0.1; 5.1 ± 0.1; 5.6 ± 0.1) and 3 human groups (Hw = 3.2 ± 0.1; 3.9 ± 0.2; 5.3 ± 0.3) were considered. The mechanical properties were measured by uniaxial tensile experiments during which the hydration of samples was the same as the hydration at which they were crosslinked. Tensile properties of 2 porcine groups (Hw = 5.1 ± 0.1; 5.6 ± 0.1) were also measured when their average hydration was lowered to 4.0 mg H2O/mg dry tissue. RESULTS The CXL procedure significantly increased tensile properties of both human and porcine samples in each hydration group (P < .05). The improvement in tensile properties was hydration-dependent, that is, samples crosslinked at higher hydration levels showed lower maximum tensile stress. The behavior of samples crosslinked at different initial hydration but tested mechanically at similar hydration showed insignificant difference (P = .7). CONCLUSION Increasing the hydration of porcine and human corneal samples before the CXL treatment had insignificant influence on tensile property improvement, as measured by testing specimens at similar hydration.
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Zhou HY, Cao Y, Wu J, Zhang WS. Role of corneal collagen fibrils in corneal disorders and related pathological conditions. Int J Ophthalmol 2017; 10:803-811. [PMID: 28546941 DOI: 10.18240/ijo.2017.05.24] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2016] [Accepted: 03/23/2017] [Indexed: 01/24/2023] Open
Abstract
The cornea is a soft tissue located at the front of the eye with the principal function of transmitting and refracting light rays to precisely sense visual information. Corneal shape, refraction, and stromal stiffness are to a large part determined by corneal fibrils, the arrangements of which define the corneal cells and their functional behaviour. However, the modality and alignment of native corneal collagen lamellae are altered in various corneal pathological states such as infection, injury, keratoconus, corneal scar formation, and keratoprosthesis. Furthermore, corneal recuperation after corneal pathological change is dependent on the balance of corneal collagen degradation and contraction. A thorough understanding of the characteristics of corneal collagen is thus necessary to develop viable therapies using the outcome of strategies using engineered corneas. In this review, we discuss the composition and distribution of corneal collagens as well as their degradation and contraction, and address the current status of corneal tissue engineering and the progress of corneal cross-linking.
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Affiliation(s)
- Hong-Yan Zhou
- Department of Ophthalmology, China-Japan Union Hospital of Jilin University, Changchun 130033, Jilin Province, China
| | - Yan Cao
- Department of Ophthalmology, China-Japan Union Hospital of Jilin University, Changchun 130033, Jilin Province, China
| | - Jie Wu
- Department of Ophthalmology, China-Japan Union Hospital of Jilin University, Changchun 130033, Jilin Province, China
| | - Wen-Song Zhang
- Department of Ophthalmology, the Second Hospital of Jilin University, Changchun 130000, Jilin Province, China
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Babaei B, Velasquez-Mao AJ, Thomopoulos S, Elson EL, Abramowitch SD, Genin GM. Discrete quasi-linear viscoelastic damping analysis of connective tissues, and the biomechanics of stretching. J Mech Behav Biomed Mater 2016; 69:193-202. [PMID: 28088071 DOI: 10.1016/j.jmbbm.2016.12.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Revised: 12/14/2016] [Accepted: 12/20/2016] [Indexed: 01/15/2023]
Abstract
The time- and frequency-dependent properties of connective tissue define their physiological function, but are notoriously difficult to characterize. Well-established tools such as linear viscoelasticity and the Fung quasi-linear viscoelastic (QLV) model impose forms on responses that can mask true tissue behavior. Here, we applied a more general discrete quasi-linear viscoelastic (DQLV) model to identify the static and dynamic time- and frequency-dependent behavior of rabbit medial collateral ligaments. Unlike the Fung QLV approach, the DQLV approach revealed that energy dissipation is elevated at a loading period of ∼10s. The fitting algorithm was applied to the entire loading history on each specimen, enabling accurate estimation of the material's viscoelastic relaxation spectrum from data gathered from transient rather than only steady states. The application of the DQLV method to cyclically loading regimens has broad applicability for the characterization of biological tissues, and the results suggest a mechanistic basis for the stretching regimens most favored by athletic trainers.
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Affiliation(s)
- Behzad Babaei
- Department of Mechanical Engineering & Materials Science, and NSF Center for Engineering MechanoBiology, Washington University in St. Louis, St. Louis, MO, USA
| | | | - Stavros Thomopoulos
- Orthopaedic Surgery, School of Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Elliot L Elson
- Department of Biochemistry & Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, USA
| | - Steven D Abramowitch
- Musculoskeletal Research Center, Department of Bioengineering, University of Pittsburgh Pittsburgh, USA
| | - Guy M Genin
- Department of Mechanical Engineering & Materials Science, and NSF Center for Engineering MechanoBiology, Washington University in St. Louis, St. Louis, MO, USA.
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Brey Gil CS, Patricio PS, Oliveira LCA, Oréfice RL. Improved self-healing properties of collagen using polyurethane microcapsules containing reactive diisocyanate. POLYM INT 2016. [DOI: 10.1002/pi.5134] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Camila Silva Brey Gil
- Department of Metallurgical and Materials Engineering; Federal University of Minas Gerais (UFMG); Brazil
| | | | - Luiz CA Oliveira
- Department of Chemistry; Federal University of Minas Gerais (UFMG); Brazil
| | - Rodrigo Lambert Oréfice
- Department of Metallurgical and Materials Engineering; Federal University of Minas Gerais (UFMG); Brazil
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