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Han X, Li M, Zhao J, Sun B, Zhang X, Xu H, Zhou X. Hydroxyproline Concentration and Associated Factors of Preserved Small Incision Lenticule Extraction-Derived Corneal Stromal Lenticules. Cornea 2024:00003226-990000000-00604. [PMID: 38967494 DOI: 10.1097/ico.0000000000003615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Accepted: 05/12/2024] [Indexed: 07/06/2024]
Abstract
PURPOSE To evaluate changes of hydroxyproline concentration and its influencing factors of small incision lenticule extraction (SMILE)-derived corneal stromal lenticules with different preservation methods. METHODS A total of 390 corneal stromal lenticules of 195 patients were derived from SMILE surgeries. Thirty of the lenticules were classified as the fresh (control) group, and the rest were randomly and evenly divided and stored in anhydrous glycerol, silicone oil, Optisol, and cryopreservation for 1 day, 1 week, or 1 month. A hydroxyproline assay kit (ab222941, Abcam) was used to measure the hydroxyproline concentration in each preservation method. Concentrations of MMP-2, TIMP-2, TNFα, TGFβ2, and reactive oxygen species were also evaluated. RESULTS In the anhydrous glycerol group, the concentration of hydroxyproline decreased within 1 week (fresh: 1 dΔ = 0.229, P < 0.001*; 1 d - 1 wΔ = 0.055, P < 0.001*) while that in the silicone oil group remained stable in 1 week (1 d - 1 wΔ = -0.005, P = 0.929) and decreased significantly in 1 m (1 m - 1 wΔ = -0.041, P = 0.003*). The sequence of hydroxyproline concentration in the Optisol group was 1 m > 1 day > 1 week. Hydroxyproline concentration in the cryopreservation group decreased within 1 m. Hydroxyproline concentration was highest in the Optisol group and lowest in the anhydrous glycerol group under the same preservation time. Hydroxyproline concentration was negatively correlated with MMP-2 (r = -0.16, P = 0.421) and TIMP-2 (r = -0.56, P = 0.002*) while MMP-2 and TNFα (r = 0.17, P = 0.242), TIMP-2 and TGFβ2 (r = 0.21, P = 0.207), and TNFα and reactive oxygen species (r = 0.52, P = 0.007*) were positively correlated. CONCLUSIONS More collagen was retained in SMILE lenticules preserved in Optisol under the same preservation time. The mechanism of the changes of collagen in preserved SMILE-derived lenticules and oxidative stress requires additional investigation.
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Affiliation(s)
- Xiaosong Han
- Eye Institute and Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, China
- NHC Key Laboratory of Myopia (Fudan University), Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China
- Shanghai Research Center of Ophthalmology and Optometry, Shanghai, China; and
- Shanghai Engineering Research Center of Laser and Autostereoscopic 3D for Vision Care, Shanghai, China
| | - Meiyan Li
- Eye Institute and Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, China
- NHC Key Laboratory of Myopia (Fudan University), Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China
- Shanghai Research Center of Ophthalmology and Optometry, Shanghai, China; and
- Shanghai Engineering Research Center of Laser and Autostereoscopic 3D for Vision Care, Shanghai, China
| | - Jing Zhao
- Eye Institute and Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, China
- NHC Key Laboratory of Myopia (Fudan University), Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China
- Shanghai Research Center of Ophthalmology and Optometry, Shanghai, China; and
- Shanghai Engineering Research Center of Laser and Autostereoscopic 3D for Vision Care, Shanghai, China
| | - Bingqing Sun
- Eye Institute and Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, China
- NHC Key Laboratory of Myopia (Fudan University), Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China
- Shanghai Research Center of Ophthalmology and Optometry, Shanghai, China; and
- Shanghai Engineering Research Center of Laser and Autostereoscopic 3D for Vision Care, Shanghai, China
| | - Xiaoyu Zhang
- Eye Institute and Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, China
- NHC Key Laboratory of Myopia (Fudan University), Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China
- Shanghai Research Center of Ophthalmology and Optometry, Shanghai, China; and
- Shanghai Engineering Research Center of Laser and Autostereoscopic 3D for Vision Care, Shanghai, China
| | - Haipeng Xu
- Eye Institute and Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, China
- NHC Key Laboratory of Myopia (Fudan University), Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China
- Shanghai Research Center of Ophthalmology and Optometry, Shanghai, China; and
- Shanghai Engineering Research Center of Laser and Autostereoscopic 3D for Vision Care, Shanghai, China
| | - Xingtao Zhou
- Eye Institute and Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, China
- NHC Key Laboratory of Myopia (Fudan University), Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China
- Shanghai Research Center of Ophthalmology and Optometry, Shanghai, China; and
- Shanghai Engineering Research Center of Laser and Autostereoscopic 3D for Vision Care, Shanghai, China
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Mascolini MV, Toniolo I, Carniel EL, Fontanella CG. Ex vivo, in vivo and in silico studies of corneal biomechanics: a systematic review. Phys Eng Sci Med 2024; 47:403-441. [PMID: 38598066 PMCID: PMC11166853 DOI: 10.1007/s13246-024-01403-2] [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: 11/09/2023] [Accepted: 02/08/2024] [Indexed: 04/11/2024]
Abstract
Healthy cornea guarantees the refractive power of the eye and the protection of the inner components, but injury, trauma or pathology may impair the tissue shape and/or structural organization and therefore its material properties, compromising its functionality in the ocular visual process. It turns out that biomechanical research assumes an essential role in analysing the morphology and biomechanical response of the cornea, preventing pathology occurrence, and improving/optimising treatments. In this review, ex vivo, in vivo and in silico methods for the corneal mechanical characterization are reported. Experimental techniques are distinct in testing mode (e.g., tensile, inflation tests), samples' species (human or animal), shape and condition (e.g., healthy, treated), preservation methods, setup and test protocol (e.g., preconditioning, strain rate). The meaningful results reported in the pertinent literature are discussed, analysing differences, key features and weaknesses of the methodologies adopted. In addition, numerical techniques based on the finite element method are reported, incorporating the essential steps for the development of corneal models, such as geometry, material characterization and boundary conditions, and their application in the research field to extend the experimental results by including further relevant aspects and in the clinical field for diagnostic procedure, treatment and planning surgery. This review aims to analyse the state-of-art of the bioengineering techniques developed over the years to study the corneal biomechanics, highlighting their potentiality to improve diagnosis, treatment and healing process of the corneal tissue, and, at the same, pointing out the current limits in the experimental equipment and numerical tools that are not able to fully characterize in vivo corneal tissues non-invasively and discourage the use of finite element models in daily clinical practice for surgical planning.
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Affiliation(s)
- Maria Vittoria Mascolini
- Department of Industrial Engineering, University of Padova, Padova, Italy
- Centre for Mechanics of Biological Materials, University of Padova, Padova, Italy
| | - Ilaria Toniolo
- Department of Industrial Engineering, University of Padova, Padova, Italy.
- Centre for Mechanics of Biological Materials, University of Padova, Padova, Italy.
| | - Emanuele Luigi Carniel
- Department of Industrial Engineering, University of Padova, Padova, Italy
- Centre for Mechanics of Biological Materials, University of Padova, Padova, Italy
| | - Chiara Giulia Fontanella
- Department of Industrial Engineering, University of Padova, Padova, Italy
- Centre for Mechanics of Biological Materials, University of Padova, Padova, Italy
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3
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魏 俊, 陈 鹏, 韩 鹏, 刘 晓, 侯 杰, 武 策, 宋 婕, 陈 维, 李 晓. [Anisotropy and viscoelasticity of different corneal regions in rabbit corneal ectasia model]. SHENG WU YI XUE GONG CHENG XUE ZA ZHI = JOURNAL OF BIOMEDICAL ENGINEERING = SHENGWU YIXUE GONGCHENGXUE ZAZHI 2024; 41:129-135. [PMID: 38403613 PMCID: PMC10894728 DOI: 10.7507/1001-5515.202312022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Revised: 12/27/2023] [Indexed: 02/27/2024]
Abstract
The mechanical properties of the cornea in corneal ectasia disease undergo a significant reduction, yet the alterations in mechanical properties within distinct corneal regions remain unclear. In this study, we established a rabbit corneal ectasia model by employing collagenase II to degrade the corneal matrix within a central diameter of 6 mm. Optical coherence tomography was employed for the in vivo assessment of corneal morphology (corneal thickness and corneal curvature) one month after operation. Anisotropy and viscoelastic characteristics of corneal tissue were evaluated through biaxial and uniaxial testing, respectively. The results demonstrated a marked decrease in central corneal thickness, with no significant changes observed in corneal curvature. Under different strains, the elastic modulus of the cornea exhibited no significant differences in the up-down and naso-temporal directions between the control and model groups. However, the cornea in the model group displayed a significantly lower elastic modulus compared to the control group. Specifically, the elastic modulus of the central region cornea in the model group was significantly lower than that of the entire cornea within the same group. Moreover, in comparison to the control group, the cornea in the model group exhibited a significant increase in both creep rate and overall deformation rate. The instantaneous modulus and equilibrium modulus were significantly reduced in the model cornea. No significant differences were observed between the entire cornea and the central cornea concerning these parameters. The results indicate that corneal anisotropy remains unchanged in collagenase-induced ectatic cornea. However, a significant reduction in viscoelastic properties is noticed. This study provides valuable insights for investigating changes in corneal mechanical properties within different regions of ectatic corneal disease.
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Affiliation(s)
- 俊超 魏
- 太原理工大学 生物医学工程学院(太原 030024)College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024, P. R. China
| | - 鹏 陈
- 太原理工大学 生物医学工程学院(太原 030024)College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024, P. R. China
| | - 鹏飞 韩
- 太原理工大学 生物医学工程学院(太原 030024)College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024, P. R. China
| | - 晓娜 刘
- 太原理工大学 生物医学工程学院(太原 030024)College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024, P. R. China
| | - 杰 侯
- 太原理工大学 生物医学工程学院(太原 030024)College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024, P. R. China
| | - 策 武
- 太原理工大学 生物医学工程学院(太原 030024)College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024, P. R. China
| | - 婕 宋
- 太原理工大学 生物医学工程学院(太原 030024)College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024, P. R. China
| | - 维毅 陈
- 太原理工大学 生物医学工程学院(太原 030024)College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024, P. R. China
| | - 晓娜 李
- 太原理工大学 生物医学工程学院(太原 030024)College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024, P. R. China
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4
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Wang C, Shen M, Song Y, Chang L, Yang Y, Li Y, Liu T, Wang Y. Biaxial hyperelastic and anisotropic behaviors of the corneal anterior central stroma along the preferential fibril orientations. Part I: Measurement and calibration of personalized stress-strain curves. Exp Eye Res 2023; 236:109677. [PMID: 37827443 DOI: 10.1016/j.exer.2023.109677] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 09/09/2023] [Accepted: 10/09/2023] [Indexed: 10/14/2023]
Abstract
Lacking specimens is the biggest limitation of studying the mechanical behaviors of human corneal. Extracting stress-strain curves is the crucial step in investigating hyperelastic and anisotropic properties of human cornea. 15 human corneal specimens extracted from the small incision lenticule extraction (SMILE) surgery were applied in this study. To accurately measure the personalized true stress-strain curve using corneal lenticules, the digital image correlation (DIC) method and finite element method were used to calibrate the stress and the strain of the biaxial extension test. The hyperelastic load-displacement curves obtained from the biaxial extension test were performed in preferential fibril orientations, which are arranged along the nasal-temporal (NT) and the superior-inferior (SI) directions within the anterior central stroma. The displacement and strain fields were accurately calibrated and calculated using the digital image correlation (DIC) method. A conversion equation was given to convert the effective engineering strain to the true strain. The stress field distribution, which was simulated using the finite element method, was verified. Based on this, the effective nominal stress with personalized characteristics was calibrated. The personalized stress-strain curves containing individual characteristic, like diopter and anterior surface curvature, was accurately measured in this study. These results provide an experimental method using biaxial tensile test with corneal lenticules. It is the foundation for investigating the hyperelasticity and anisotropy of the central anterior stroma of human cornea.
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Affiliation(s)
- Congzheng Wang
- Department of Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin, 300350, China
| | - Min Shen
- Department of Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin, 300350, China.
| | - Yi Song
- Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin Eye Institute, Nankai University Affiliated Eye Hospital, Nankai University, Tianjin, 300020, China; Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, 300070, China
| | - Le Chang
- Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin Eye Institute, Nankai University Affiliated Eye Hospital, Nankai University, Tianjin, 300020, China; Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, 300070, China
| | - Yaqing Yang
- Department of Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin, 300350, China
| | - Yikuan Li
- Department of Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin, 300350, China
| | - Taiwei Liu
- Department of Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin, 300350, China; Department of Engineering Mechanics, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, 800 Dong Chuan Road, Shanghai, 200240, China
| | - Yan Wang
- Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin Eye Institute, Nankai University Affiliated Eye Hospital, Nankai University, Tianjin, 300020, China; Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, 300070, China
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Nambiar MH, Liechti L, Studer H, Roy AS, Seiler TG, Büchler P. Patient-specific finite element analysis of human corneal lenticules: An experimental and numerical study. J Mech Behav Biomed Mater 2023; 147:106141. [PMID: 37748318 DOI: 10.1016/j.jmbbm.2023.106141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Revised: 05/05/2023] [Accepted: 09/20/2023] [Indexed: 09/27/2023]
Abstract
The number of elective refractive surgeries is constantly increasing due to the drastic increase in myopia prevalence. Since corneal biomechanics are critical to human vision, accurate modeling is essential to improve surgical planning and optimize the results of laser vision correction. In this study, we present a numerical model of the anterior cornea of young patients who are candidates for laser vision correction. Model parameters were determined from uniaxial tests performed on lenticules of patients undergoing refractive surgery by means of lenticule extraction, using patient-specific models of the lenticules. The models also took into account the known orientation of collagen fibers in the tissue, which have an isotropic distribution in the corneal plane, while they are aligned along the corneal curvature and have a low dispersion outside the corneal plane. The model was able to reproduce the experimental data well with only three parameters. These parameters, determined using a realistic fiber distribution, yielded lower values than those reported in the literature. Accurate characterization and modeling of the cornea of young patients is essential to study better refractive surgery for the population undergoing these treatments, to develop in silico models that take corneal biomechanics into account when planning refractive surgery, and to provide a basis for improving visual outcomes in the rapidly growing population undergoing these treatments.
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Affiliation(s)
- Malavika H Nambiar
- ARTORG Center for Biomedical Engineering Research, University of Bern, Freiburgstrasse 3, 3010, Bern, Switzerland.
| | - Layko Liechti
- ARTORG Center for Biomedical Engineering Research, University of Bern, Freiburgstrasse 3, 3010, Bern, Switzerland.
| | - Harald Studer
- Optimo Medical, Robert-Walser-Platz 7, 2503, Biel, Switzerland.
| | - Abhijit S Roy
- Narayana Nethralaya Eye Clinic, Bengaluru, Karnataka, 560010, India.
| | - Theo G Seiler
- IROC AG, Institut für Refraktive und Ophthalmo-Chirurgie, Stockerstrasse 37, 8002, Zürich, Switzerland; Universitätsklinik für Augenheilkunde, Inselspital Bern, Freiburgstrasse 15, 3010, Bern, Switzerland; Klinik für Augenheilkunde, Universitätsklinikum Düsseldorf, Moorenstr. 5, 40225, Düsseldorf, Germany.
| | - Philippe Büchler
- ARTORG Center for Biomedical Engineering Research, University of Bern, Freiburgstrasse 3, 3010, Bern, Switzerland.
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6
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Chen L, Huang Y, Zhang X, Shi Y, Gao Z, Sun B, Shen Y, Sun L, Cao Y, Zhang Q, Guo J, Li F, Chen W, Li X, Zhou X. Corneal Biomechanical Properties Demonstrate Anisotropy and Correlate With Axial Length in Myopic Eyes. Invest Ophthalmol Vis Sci 2023; 64:27. [PMID: 37477932 PMCID: PMC10365135 DOI: 10.1167/iovs.64.10.27] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Accepted: 06/12/2023] [Indexed: 07/22/2023] Open
Abstract
Purpose The purpose of this study was to investigate the ex vivo and in vivo biomechanical characteristic of cornea in myopic eyes. Methods Fifty-one corneal stromal lenticules were obtained from myopic eyes during the SMILE procedure and were tested by a biaxial tensile system within 24 hours postoperatively. The material properties of the lenticules were described using stress-strain curves and were compared among axial length (AL) <26 mm and AL ≥ 26 mm group. Pre-operative stress-strain index (SSI) parameters were used to evaluate the biomechanical properties of the cornea in vivo. Results Compared with AL < 26 mm, the tangent modulus significantly decreased in horizontal and vertical directions when AL ≥ 26 mm (P < 0.05); SSI also significantly decreased when AL ≥ 26 mm (P < 0.05). Anisotropic parameter is positively correlated with AL (r = 0.307, P < 0.05). Compared with AL < 26 mm, anisotropic parameter significantly increased when AL ≥ 26 mm (P < 0.05). SSI was negatively correlated with AL (r = -0.380, P < 0.05) in the AL < 26 mm group but not in the AL ≥ 26 mm group (P > 0.05). Compared with 26 mm ≤ AL < 27 mm group, the tangent modulus significantly decreased in the horizontal direction (P < 0.05) but not in the vertical direction when 27 mm ≤ AL < 28 mm (P > 0.05). Conclusions The biomechanical properties of cornea decreased with the increase of AL. Tangent modulus significantly decreased in the horizontal direction compared with vertical direction. AL should be taken into account during calculation of corneal biomechanical parameters in order to improve validity.
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Affiliation(s)
- Lingfeng Chen
- College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan, Shanxi, China
| | - Yangyi Huang
- Eye Institute and Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, China
- NHC Key Laboratory of Myopia (Fudan University); Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China
- Shanghai Research Center of Ophthalmology and Optometry, Shanghai, China
- Shanghai Engineering Research Center of Laser and Autostereoscopic 3D for Vision Care (20DZ2255000), Shanghai, China
| | - Xiaoyu Zhang
- Eye Institute and Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, China
- NHC Key Laboratory of Myopia (Fudan University); Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China
- Shanghai Research Center of Ophthalmology and Optometry, Shanghai, China
- Shanghai Engineering Research Center of Laser and Autostereoscopic 3D for Vision Care (20DZ2255000), Shanghai, China
| | - Yike Shi
- College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan, Shanxi, China
| | - Zhipeng Gao
- College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan, Shanxi, China
| | - Bingqing Sun
- Eye Institute and Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, China
- NHC Key Laboratory of Myopia (Fudan University); Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China
- Shanghai Research Center of Ophthalmology and Optometry, Shanghai, China
- Shanghai Engineering Research Center of Laser and Autostereoscopic 3D for Vision Care (20DZ2255000), Shanghai, China
| | - Yang Shen
- Eye Institute and Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, China
- NHC Key Laboratory of Myopia (Fudan University); Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China
- Shanghai Research Center of Ophthalmology and Optometry, Shanghai, China
- Shanghai Engineering Research Center of Laser and Autostereoscopic 3D for Vision Care (20DZ2255000), Shanghai, China
| | - Ling Sun
- Eye Institute and Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, China
- NHC Key Laboratory of Myopia (Fudan University); Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China
- Shanghai Research Center of Ophthalmology and Optometry, Shanghai, China
- Shanghai Engineering Research Center of Laser and Autostereoscopic 3D for Vision Care (20DZ2255000), Shanghai, China
| | - Yifan Cao
- College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan, Shanxi, China
| | - Qianqian Zhang
- College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan, Shanxi, China
- Shanxi Bethune Hospital, Shanxi Academy of Medical Sciences, Tongji Shanxi Hospital, Third Hospital of Shanxi Medical University, Taiyuan, China
- School of Automation and Software Engineering, Shanxi University, Taiyuan, Shanxi, China
| | - Jiqiang Guo
- Shanxi Bethune Hospital, Shanxi Academy of Medical Sciences, Tongji Shanxi Hospital, Third Hospital of Shanxi Medical University, Taiyuan, China
| | - Fen Li
- College of Mechanical and Vehicle Engineering, Taiyuan University of Technology, Taiyuan, China
- Institute of Applied Mechanics, Taiyuan University of Technology, Taiyuan, China
| | - Weiyi Chen
- College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan, Shanxi, China
| | - Xiaona Li
- College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan, Shanxi, China
| | - Xingtao Zhou
- Eye Institute and Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, China
- NHC Key Laboratory of Myopia (Fudan University); Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China
- Shanghai Research Center of Ophthalmology and Optometry, Shanghai, China
- Shanghai Engineering Research Center of Laser and Autostereoscopic 3D for Vision Care (20DZ2255000), Shanghai, China
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7
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Lan G, Twa MD, Song C, Feng J, Huang Y, Xu J, Qin J, An L, Wei X. In vivo corneal elastography: A topical review of challenges and opportunities. Comput Struct Biotechnol J 2023; 21:2664-2687. [PMID: 37181662 PMCID: PMC10173410 DOI: 10.1016/j.csbj.2023.04.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 04/07/2023] [Accepted: 04/12/2023] [Indexed: 05/16/2023] Open
Abstract
Clinical measurement of corneal biomechanics can aid in the early diagnosis, progression tracking, and treatment evaluation of ocular diseases. Over the past two decades, interdisciplinary collaborations between investigators in optical engineering, analytical biomechanical modeling, and clinical research has expanded our knowledge of corneal biomechanics. These advances have led to innovations in testing methods (ex vivo, and recently, in vivo) across multiple spatial and strain scales. However, in vivo measurement of corneal biomechanics remains a long-standing challenge and is currently an active area of research. Here, we review the existing and emerging approaches for in vivo corneal biomechanics evaluation, which include corneal applanation methods, such as ocular response analyzer (ORA) and corneal visualization Scheimpflug technology (Corvis ST), Brillouin microscopy, and elastography methods, and the emerging field of optical coherence elastography (OCE). We describe the fundamental concepts, analytical methods, and current clinical status for each of these methods. Finally, we discuss open questions for the current state of in vivo biomechanics assessment techniques and requirements for wider use that will further broaden our understanding of corneal biomechanics for the detection and management of ocular diseases, and improve the safety and efficacy of future clinical practice.
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Affiliation(s)
- Gongpu Lan
- Guangdong-Hong Kong-Macao Intelligent Micro-Nano Optoelectronic Technology Joint Laboratory, School of Physics and Optoelectronic Engineering, Foshan University, Foshan, Guangdong 528000, China
- Weiren Meditech Co., Ltd., Foshan, Guangdong 528000, China
| | - Michael D Twa
- College of Optometry, University of Houston, Houston, TX 77204, United States
| | - Chengjin Song
- Guangdong-Hong Kong-Macao Intelligent Micro-Nano Optoelectronic Technology Joint Laboratory, School of Physics and Optoelectronic Engineering, Foshan University, Foshan, Guangdong 528000, China
| | - JinPing Feng
- Institute of Engineering and Technology, Hubei University of Science and Technology, Xianning, Hubei 437100, China
| | - Yanping Huang
- Guangdong-Hong Kong-Macao Intelligent Micro-Nano Optoelectronic Technology Joint Laboratory, School of Physics and Optoelectronic Engineering, Foshan University, Foshan, Guangdong 528000, China
- Weiren Meditech Co., Ltd., Foshan, Guangdong 528000, China
| | - Jingjiang Xu
- Guangdong-Hong Kong-Macao Intelligent Micro-Nano Optoelectronic Technology Joint Laboratory, School of Physics and Optoelectronic Engineering, Foshan University, Foshan, Guangdong 528000, China
- Weiren Meditech Co., Ltd., Foshan, Guangdong 528000, China
| | - Jia Qin
- Weiren Meditech Co., Ltd., Foshan, Guangdong 528000, China
| | - Lin An
- Weiren Meditech Co., Ltd., Foshan, Guangdong 528000, China
| | - Xunbin Wei
- Biomedical Engineering Department, Peking University, Beijing 100081, China
- International Cancer Institute, Peking University, Beijing 100191, China
- Institute of Medical Technology, Peking University Health Science Center, Beijing 100191, China
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8
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Wang C, Shen M, Song Y, Chang L, Yang Y, Li Y, Liu T, Wang Y. Biaxial hyperelastic and anisotropic behaviors of the corneal anterior central stroma along the preferential fibril orientations. Part II: Quantitative computational analysis of mechanical response of stromal components. J Mech Behav Biomed Mater 2023; 142:105802. [PMID: 37043981 DOI: 10.1016/j.jmbbm.2023.105802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 03/20/2023] [Accepted: 03/23/2023] [Indexed: 03/30/2023]
Abstract
To study the hyperelastic and anisotropic behaviors of the central anterior stroma for patients with myopia, 40 corneal stromal specimens extracted after small incision lenticule extraction (SMILE) surgery were used in the biaxial extension test along two preferential fibril orientations. An improved collagen fibril crimping constitutive model with a specific physical meaning was proposed to analyze the hyperelasticity and anisotropy of the stroma. The effective elastic modulus of the two families of preferentially oriented collagen fibrils and the stiffness of the non-collagenous matrix along all three directions were compared according to the specific physical meaning of the parameters. Anisotropic behavior was found in the hyperelastic properties of the corneal anterior central stroma in the preferential fibril orientations. The stiffness of non-collagenous matrix is significantly larger in the optical axis direction than in the nasal-temporal (NT) and superior-inferior (SI) directions. Moreover, individual differences between males and females slightly impact on hyperelastic and anisotropic behaviors. The differences of these behaviors were significant in the comparison of the left and right eyes. These results have a guiding significance for the accurate design of surgical plans for refractive surgery according to a patient's condition and have a driving value for the further exploration of the biomechanical properties of the whole cornea.
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Chang L, Zhang L, Cheng Z, Zhang N, Wang C, Wang Y, Liu W. Effectiveness of collagen cross-linking induced by two-photon absorption properties of a femtosecond laser in ex vivo human corneal stroma. BIOMEDICAL OPTICS EXPRESS 2022; 13:5067-5081. [PMID: 36187250 PMCID: PMC9484424 DOI: 10.1364/boe.468593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 08/20/2022] [Accepted: 08/22/2022] [Indexed: 06/16/2023]
Abstract
This study aimed to investigate the effectiveness of two-photon induced collagen cross-linking (CXL) using femtosecond lasers in human corneal stroma. An 800-nm femtosecond laser optical path for CXL was established. Corneal samples that received two-photon induced CXL and ultraviolet-A (UVA) CXL underwent uniaxial stretching experiments, proteolytic resistance assays and observation of collagen fiber structure changes. Two-photon induced CXL can achieve corneal stiffening effects comparable to UVA CXL and showed better advantages at low strains. The cornea after two-photon induced CXL exhibited high enzymatic resistance and tight collagen fiber arrangement. Two-photon induced CXL promises to be a new option for keratoconus.
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Affiliation(s)
- Le Chang
- Clinical College of Ophthalmology, Tianjin Medical University, No. 22 Meteorological Terrace Road, Heping District, Tianjin 300070, China
| | - Lin Zhang
- Clinical College of Ophthalmology, Tianjin Medical University, No. 22 Meteorological Terrace Road, Heping District, Tianjin 300070, China
- Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin Eye Institute, Nankai University Affiliated Eye Hospital, Nankai University, No. 4 Gansu Road, Heping District, Tianjin 300020, China
| | - Zhenzhou Cheng
- Institute of Modern Optics, Nankai University, No. 94 Weijin Road, Nankai District, Tianjin 300071, China
- Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, No. 94 Weijin Road, Nankai District, Tianjin 300071, China
| | - Nan Zhang
- Institute of Modern Optics, Nankai University, No. 94 Weijin Road, Nankai District, Tianjin 300071, China
- Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, No. 94 Weijin Road, Nankai District, Tianjin 300071, China
| | - Congzheng Wang
- Department of Mechanics, School of Mechanical Engineering, Tianjin University, No. 92 Weijin Road, Nankai District, Tianjin 300072, China
| | - Yan Wang
- Clinical College of Ophthalmology, Tianjin Medical University, No. 22 Meteorological Terrace Road, Heping District, Tianjin 300070, China
- Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin Eye Institute, Nankai University Affiliated Eye Hospital, Nankai University, No. 4 Gansu Road, Heping District, Tianjin 300020, China
| | - Weiwei Liu
- Institute of Modern Optics, Nankai University, No. 94 Weijin Road, Nankai District, Tianjin 300071, China
- Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, No. 94 Weijin Road, Nankai District, Tianjin 300071, China
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Song Y, Wu D, Shen M, Wang L, Wang C, Cai Y, Xue C, Cheng GPM, Zheng Y, Wang Y. Measuring Human Corneal Stromal Biomechanical Properties Using Tensile Testing Combined With Optical Coherence Tomography. Front Bioeng Biotechnol 2022; 10:882392. [PMID: 35669060 PMCID: PMC9163803 DOI: 10.3389/fbioe.2022.882392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Accepted: 05/02/2022] [Indexed: 11/30/2022] Open
Abstract
Purpose: To investigate the ex vivo elastic modulus of human corneal stroma using tensile testing with optical coherence tomography (OCT) imaging and its correlation with in vivo measurements using corneal visualization Scheimpflug technology. Methods: Twenty-four corneal specimens extracted from stromal lenticules through small incision lenticule extraction were cut into strips for uniaxial tensile tests. In vivo corneal biomechanical responses were evaluated preoperatively using the corneal visualization Scheimpflug technology (CorVis ST). The correlation of the elastic modulus with clinical characteristics and dynamic corneal response parameters were analyzed using Spearman’s correlation analysis. Results: The mean low strain tangent modulus (LSTM) of the human corneal stroma was 0.204 ± 0.189 (range 0.010–0.641) MPa, and high strain tangent modulus (HSTM) 5.114 ± 1.958 (range 2.755–9.976) MPa. Both LSTM (r = 0.447, p = 0.029) and HSTM (r = 0.557, p = 0.005) were positively correlated with the stress-strain index (SSI). LSTM was also positively correlated with the A1 deflection length (r = 0.427, p = 0.037) and A1 deflection area (r = 0.441, p = 0.031). HSTM was positively correlated with spherical equivalent (r = 0.425, p = 0.038). Conclusions: The correlation of corneal elastic modulus with A1 deflection parameters and SSI may indicate a relationship between these parameters and tissue elasticity. The HSTM decreased with the degree of myopia. Combining tensile test with OCT may be a promising approach to assess corneal biomechanical properties.
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Affiliation(s)
- Yi Song
- Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, China
| | - Di Wu
- Tianjin Eye Hospital, Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Institute, Tianjin, China.,Pacific University College of Optometry, Forest Grove, OR, United States
| | - Min Shen
- School of Mechanical Engineering, Tianjin University, Tianjin, China
| | - Like Wang
- Department of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong, China
| | - Congzheng Wang
- School of Mechanical Engineering, Tianjin University, Tianjin, China
| | - Yong Cai
- Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, China
| | - Chao Xue
- Tianjin Eye Hospital, Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Institute, Tianjin, China
| | - George P M Cheng
- School of Optometry, The Hong Kong Polytechnic University, Hong Kong, China
| | - Yongping Zheng
- Department of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong, China.,Research Institute for Smart Ageing, The Hong Kong Polytechnic University, Hong Kong, China
| | - Yan Wang
- Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, China.,Tianjin Eye Hospital, Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Institute, Tianjin, China.,Nankai University Eye Institute, Nankai University Affiliated Eye Hospital, Nankai University, Tianjin, China
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Peyman A, Ghoreishi M, Hashemi-Estabragh SS, Mirmohammadkhani M, Mohammadinia M, Pourazizi M. Corneal biomechanical properties after soft contact lens wear measured on a dynamic Scheimpflug analyzer: A before and after study. J Fr Ophtalmol 2021; 44:391-396. [PMID: 33618908 DOI: 10.1016/j.jfo.2020.06.050] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 06/02/2020] [Accepted: 06/08/2020] [Indexed: 11/16/2022]
Abstract
OBJECTIVES To evaluate the corneal biomechanics before and after daily use of contact lenses (CLs), measured by Scheimpflug-based devices. METHODS This prospective clinical study includes participants who were scheduled to use CLs daily for refractive error. The biomechanical parameters were measured by the Corneal Visualization Scheimpflug Technology (Corvis ST) before and one month after using the soft CLs. RESULTS Twenty-three subjects (46 eyes), including 16 female (76.2%) with a mean age of 28±7.29 years, were enrolled. There was no significant difference among biomechanical factors measured before and after contact lens wear (P>0.05). Using regression analysis of the biomechanical markers, we found a statistically significant association between second applanation length (A2 length) (P=0.001), highest concavity radius (HCR) (P=0.05), deflection amplitude ratio (DA_ratio) (P=0.05) and integrated radius (P<0.001) with age. Regarding spherical equivalent, we found a statistically significant association between central corneal thickness (CCT) (P=0.05), A2 length (P=0.03) and stiffness parameter at first applanation (SPA1) (P=0.02). CONCLUSIONS We did not find a significant difference in terms of corneal biomechanical parameters between baseline and month 1; but regression analyses showed a statistically significant association between A2 length, HCR, DA_ratio, integrated radius, CCT and SPA1 and certain subject characteristics.
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Affiliation(s)
- A Peyman
- Isfahan Eye Research Center, Department of Ophthalmology, Isfahan University of Medical Sciences, Feiz Hospital, Modares St., Isfahan, Iran.
| | - M Ghoreishi
- Parsian Vision Research Institute, Department of Ophthalmology, Isfahan University of Medical Sciences, Isfahan, Iran.
| | - S-S Hashemi-Estabragh
- Isfahan Eye Research Center, Department of Ophthalmology, Isfahan University of Medical Sciences, Isfahan, Iran.
| | - M Mirmohammadkhani
- Social Determinants of Health Research Center, Semnan University of Medical Sciences, Semnan, Iran And Department of Epidemiology and Biostatistics, School of Medicine, Semnan University of Medical Sciences, Semnan, Iran.
| | | | - M Pourazizi
- Isfahan Eye Research Center, Department of Ophthalmology, Isfahan University of Medical Sciences, Feiz Hospital, Modares St., Isfahan, Iran.
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Direct Evidence of Symmetry between Bilateral Human Corneas in Biomechanical Properties: A Comparison Study with Fresh Corneal Tissue. J Ophthalmol 2021. [DOI: 10.1155/2021/8891412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Purpose. To investigate the difference between the eyes from the same human with respect to the biomechanical properties of fresh corneal tissues and investigate the assumption of similarity of the corneal biomechanical properties between the eyes. Methods. Strip specimens extracted through a small incision lenticule extraction (SMILE) surgery were tested using a uniaxial tensile test. The specimens were extracted vertically. Low-strain tangent modulus (LSTM), high-strain tangent modulus (HSTM), and tensile strength () were the biomechanical parameters used in the comparison of the eyes from the same human. Results. Ninety corneal specimens from 45 persons were included in this study. The LSTM of the left and right eyes were 1.34 ± 0.52 and 1.37 ± 0.46 MPa, while the HSTM were 50.53 ± 7.51 and 49.41 ± 7.01 MPa, respectively. There was no significant difference between the eyes in terms of LSTM, HSTM, and. The LSTM and HSTM were significantly correlated with the spherical equivalent (SE) (, resp.). Conclusions. The assumption that the corneal biomechanical properties of the eyes from the same human are similar has been confirmed for the first time using fresh human corneal tissue. This finding may be useful in further biomechanical studies.
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Effect of freezing and thawing on the biomechanical characteristics of porcine ocular tissues. J Biomech 2019; 87:93-99. [PMID: 30876736 DOI: 10.1016/j.jbiomech.2019.02.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Revised: 12/25/2018] [Accepted: 02/23/2019] [Indexed: 12/13/2022]
Abstract
PURPOSE To evaluate the effect of freezing and thawing on the biomechanical properties of ex-vivo porcine ocular tissue. METHODS Thirty-six porcine eyes (18 pairs) were obtained fresh from a local abattoir and split into two groups of nine pairs to study the effect of storage at -20 °C and -80 °C. A randomly-selected eye from each pair (Control Group, CG) was tested fresh while the fellow eyes were frozen for 14 days, either at -20 °C and -80 °C (Frozen Group, FG) before thawing and testing. Seventy-two strips were extracted from the corneas and scleras of eye globes and subjected to uniaxial tension tests under loads up to 1.0 N. Following five preconditioning cycles, the load and elongation data obtained experimentally were analysed to derive the tissue's stress-strain and tangent modulus-strain behaviour. RESULTS Corneal tissue subjected to freezing at -20 °C exhibited significant increases in tangent modulus (mechanical stiffness) by 13 ± 17% (p = 0.003) at 1% strain and 14 ± 12% (p < 0.001) at 2% strain. In contrast, the increases in corneal stiffness at -80 °C were insignificant (6 ± 14%, p = 0.099 at 1% strain, 6 ± 15%, p = 0.091 at 2% strain). The corresponding increases in tangent modulus in the sclera were all insignificant (for -20 °C: 4 ± 14%, p = 0.265 at 1% strain, 3 ± 9%, p = 0.186 at 2% strain; for -80 °C: 3 ± 18%, p = 0.537 at 1% strain and 3 ± 18%, p = 0.491 at 2% strain). CONCLUSIONS The study provided evidence that freezing and thawing led to insignificant changes in ocular tissue stiffness except in corneal tissue that was frozen at -20 °C.
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