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Al Bdour M, Sabbagh HM, Jammal HM. Multi-modal imaging for the detection of early keratoconus: a narrative review. EYE AND VISION (LONDON, ENGLAND) 2024; 11:18. [PMID: 38730479 PMCID: PMC11088107 DOI: 10.1186/s40662-024-00386-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Accepted: 04/21/2024] [Indexed: 05/12/2024]
Abstract
Keratoconus is a common progressive corneal disorder that can be associated with significant ocular morbidity. Various corneal imaging techniques have been used for the diagnosis of established cases. However, in the early stages of the disease, which include subclinical keratoconus and forme fruste keratoconus, detection of such cases can be challenging. The importance of detecting such cases is very important because early intervention can halt disease progression, improve visual outcomes and prevent postrefractive surgery ectasia associated with performing corneal refractive procedures in such patients. This narrative review aimed to examine several established and evolving imaging techniques for the detection of early cases of keratoconus. The utilization of combinations of these techniques may further increase their diagnostic ability.
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Affiliation(s)
- Muawyah Al Bdour
- Department of Ophthalmology, School of Medicine, The University of Jordan, Amman, Jordan
| | - Hashem M Sabbagh
- The National Center for Diabetes Endocrinology and Genetics (NCDEG), Amman, Jordan
| | - Hisham M Jammal
- Department of Ophthalmology, Faculty of Medicine, Jordan University of Science and Technology, PO Box 3030, Irbid, 22110, Jordan.
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Syed ZA, Milman T, Fertala J, Steplewski A, Fertala A. Corneal Wound Healing in the Presence of Antifibrotic Antibody Targeting Collagen Fibrillogenesis: A Pilot Study. Int J Mol Sci 2023; 24:13438. [PMID: 37686240 PMCID: PMC10488077 DOI: 10.3390/ijms241713438] [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: 07/06/2023] [Revised: 08/16/2023] [Accepted: 08/25/2023] [Indexed: 09/10/2023] Open
Abstract
Highly organized collagen fibrils interlacing with proteoglycans form the crucial architecture of the cornea and facilitate its transparency. Corneal scarring from accidental injury, surgery, or infection alters this highly organized tissue, causing severe consequences, including blindness. There are no pharmacological or surgical methods to effectively and safely treat excessive corneal scarring. Thus, we tested the anticorneal scarring utility of a rationally designed anticollagen antibody (ACA) whose antifibrotic effects have already been demonstrated in nonocular models. Utilizing a rabbit model with an incisional corneal wound, we analyzed ACA's effects on forming collagen and proteoglycan-rich extracellular matrices in scar neotissue. We used microscopic and spectroscopic techniques to quantify these components and measure crucial parameters characterizing the structure and organization of collagen fibrils. Moreover, we analyzed the spatial distribution of collagen and proteoglycans in normal and healing corneas. Our study demonstrated significant changes in the quality and quantity of the analyzed molecules synthesized in scar neotissue. It showed that these changes extend beyond incision margins. It also showed ACA's positive impact on some crucial parameters defining proper cornea structure. This pilot study provides a stepping stone for future tests of therapeutic approaches that target corneal extracellular scar matrix assembly.
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Affiliation(s)
- Zeba A. Syed
- Wills Eye Hospital, Philadelphia, PA 19107, USA; (Z.A.S.); (T.M.)
| | - Tatyana Milman
- Wills Eye Hospital, Philadelphia, PA 19107, USA; (Z.A.S.); (T.M.)
| | - Jolanta Fertala
- Department of Orthopaedic Surgery, Sidney Kimmel Medical College, Thomas Jefferson University, Curtis Building, Room 501, 1015 Walnut Street, Philadelphia, PA 19107, USA; (J.F.); (A.S.)
| | - Andrzej Steplewski
- Department of Orthopaedic Surgery, Sidney Kimmel Medical College, Thomas Jefferson University, Curtis Building, Room 501, 1015 Walnut Street, Philadelphia, PA 19107, USA; (J.F.); (A.S.)
| | - Andrzej Fertala
- Department of Orthopaedic Surgery, Sidney Kimmel Medical College, Thomas Jefferson University, Curtis Building, Room 501, 1015 Walnut Street, Philadelphia, PA 19107, USA; (J.F.); (A.S.)
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Biomechanics of keratoconus: Two numerical studies. PLoS One 2023; 18:e0278455. [PMID: 36730305 PMCID: PMC9894483 DOI: 10.1371/journal.pone.0278455] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Accepted: 11/16/2022] [Indexed: 02/03/2023] Open
Abstract
BACKGROUND The steep cornea in keratoconus can greatly impair eyesight. The etiology of keratoconus remains unclear but early injury that weakens the corneal stromal architecture has been implicated. To explore keratoconus mechanics, we conducted two numerical simulation studies. METHODS A finite-element model describing the five corneal layers and the heterogeneous mechanical behaviors of the ground substance and lamellar collagen-fiber architecture in the anterior and posterior stroma was developed using the Holzapfel-Gasser-Ogden constitutive model. The geometry was from a healthy subject. Its stroma was divided into anterior, middle, and posterior layers to assess the effect of changing regional mechanical parameters on corneal displacement and maximum principal stress under intraocular pressure. Specifically, the effect of softening an inferocentral corneal button, the collagen-based tissues throughout the whole cornea, or specific stromal layers in the button was examined. The effect of simply disorganizing the orthogonally-oriented posterior stromal fibers in the button was also assessed. The healthy cornea was also subjected to eye rubbing-like loading to identify the corneal layer(s) that experienced the most tensional stress. RESULTS Conical deformation and corneal thinning emerged when the corneal button or the mid-posterior stroma of the button underwent gradual softening or when the collagen fibers in the mid-posterior stroma of the button were dispersed. Softening the anterior layers of the button or the whole cornea did not evoke conical deformation. Button softening greatly increased and disrupted the stress on Bowman's membrane while mid-posterior stromal softening increased stress in the anterior layers. Eye rubbing profoundly stressed the deep posterior stroma while other layers were negligibly affected. DISCUSSION These observations suggest that keratoconus could be initiated, at least partly, by mechanical instability/damage in the mid-posterior stroma that then imposes stress on the anterior layers. This may explain why subclinical keratoconus is marked by posterior but not anterior elevation on videokeratoscopy.
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Cheng Z, Zhang N, Chang L, Qi P, Zhang L, Lin L, Wang Y, Liu W. Two-photon collagen crosslinking in ex vivo human corneal lenticules induced by near-infrared femtosecond laser. JOURNAL OF BIOPHOTONICS 2023; 16:e202200160. [PMID: 36153307 DOI: 10.1002/jbio.202200160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 08/24/2022] [Accepted: 09/21/2022] [Indexed: 06/16/2023]
Abstract
Myopia and keratoconus have become common corneal diseases that threaten the quality of human vision, and keratoconus is one of the most common indications for corneal transplantation worldwide. Collagen crosslinking (CXL) using riboflavin and ultraviolet A (UVA) light is an effective approach for treating ophthalmic disorders and has been shown clinically not only to arrest further progression of keratoconus but also to improve refractive power for cornea. However, CXL surgery irradiated by UVA has various potential risks such as surface damage and endothelial cell damage. Here, near-infrared femtosecond laser-based two-photon CXL was first applied to ex vivo human corneal stroma, operating at low photon energy with high precision and stability. After two-photon CXL, the corneal stiffness can be enhanced by 300% without significantly reducing corneal transparency. These findings illustrate the optimized direction that depositing high pulses energy in corneal focal volume (not exceeding damage threshold), and pave the way to 3D CXL of in vivo human cornea with higher safety, precision, and efficacy.
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Affiliation(s)
- Zhenzhou Cheng
- Institute of Modern Optics, Eye Institute, Nankai University, Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin, China
| | - Nan Zhang
- Institute of Modern Optics, Eye Institute, Nankai University, Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin, China
| | - Le Chang
- Tianjin Eye Hospital, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin, China
- Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, China
| | - Pengfei Qi
- Institute of Modern Optics, Eye Institute, Nankai University, Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin, China
| | - Lin Zhang
- Tianjin Eye Hospital, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin, China
- Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, China
| | - Lie Lin
- Institute of Modern Optics, Eye Institute, Nankai University, Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin, China
| | - Yan Wang
- Institute of Modern Optics, Eye Institute, Nankai University, Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin, China
- Tianjin Eye Hospital, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin, China
- Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, China
| | - Weiwei Liu
- Institute of Modern Optics, Eye Institute, Nankai University, Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin, China
- Tianjin Eye Hospital, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin, China
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Abstract
PURPOSE The relevance of corneal biomechanics and the importance of including it in the clinical assessment of corneal ectasias are being increasingly recognized. The connection between corneal ultrastructure, biomechanical properties, and optical function is exemplified by a condition like keratoconus. Biomechanical instability is seen as the underlying basis for the secondary morphological changes in the cornea. Asymmetric biomechanical weakening is believed to drive progressive corneal steepening and thinning. Biomechanical strengthening is the principle of collagen crosslinking that has been shown to effectively arrest progression of the keratoconus. Corneal biomechanics has therefore ignited the interest of researchers and clinicians alike and has given us new insights into the cause and course of the disease. This article is an overview of the extensive work published, predominantly in the last two decades, on the biomechanical aspect of keratoconus. METHODS Published articles on corneal biomechanics in the specific context of keratoconus were reviewed, based on an electronic search using PubMed, Elsevier, and Science Direct. The search terms used included "Corneal Biomechanics," "Mechanical properties of the cornea," "Corneal ultrastructure," "Corneal Collagen," and "Keratoconus". Articles pertaining to refractive surgery, keratoplasty, collagen crosslinking, or intrastromal rings were excluded. RESULTS The electronic search revealed more than 500 articles, from which 80 were chosen for this article. CONCLUSIONS The structural and organizational pattern of the corneal stroma determines its mechanical properties and are responsible for the maintenance of the normal shape and function of the cornea. Changes in the ultrastructure are responsible for the biomechanical instability that leads to corneal ectasia. As non-invasive methods for evaluating corneal biomechanics in vivo evolve, our ability to diagnose subclinical keratoconus will improve, allowing identification of patients at risk to develop ectasia and to allow early treatment to arrest progression of the disease.
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Affiliation(s)
- Prema Padmanabhan
- Department of Cornea and Refractive Surgery, Medical Research Foundation, Sankara Nethralaya, Chennai, India
| | - Ahmed Elsheikh
- School of Engineering, University of Liverpool, Liverpool, UK.,Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, China.,NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK
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Aksoy Aydemir G, Ozkoyuncu Kocabas D, Aydemir E, Bayat AH, Cınar SS, Karadağ AS. Alterations in the choroidal thickness and retinal vascular caliber in keratoconus. Int Ophthalmol 2023; 43:95-103. [PMID: 35773524 DOI: 10.1007/s10792-022-02391-6] [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: 02/24/2022] [Accepted: 06/14/2022] [Indexed: 02/07/2023]
Abstract
PURPOSE To compare the choroidal thickness (CT) and retinal vascular caliber in the differentiation of patients who have keratoconus (KC) from those of astigmatic and normal patients. METHODS This was a prospective, cross-sectional study. A total of 72 patients who had KC, 70 who had astigmatism, and 83 healthy control subjects were enrolled in this study. All the patients were examined using the Sirius topography system and spectral domain optical coherence tomography with enhanced depth imaging. Using the digital fundus photographs, the retinal vascular calibers were calculated. The measurements were also analyzed between the KC stages according to the Amsler-Krumeich classification. RESULTS The CT measurements were significantly higher in the KC group, when compared with the other 2 groups, in each location (P < 0.05). No statistically significant difference was observed with regards to the central retinal artery equivalent (CRAE) values (P = 0.959), while significant differences were noted in the central retinal vein equivalent (CRVE) among the groups (P = 0.011). Significant increases were noted in the CT as the stage of KC progressed, except at temporal 3000 µm (P = 0.603). No statistically significant difference was observed with regards to the CRAE among the stages (P = 0.901). However, the CRVE changes increased remarkably as the stages advanced (P < 0.001). CONCLUSION The patients who had KC seemed to have a thicker CT and higher CRVE values than the healthy individuals, and these differences were progressively increased as the stages of KC advanced. Reflecting the vascular effects of inflammation, the high CRVE supported theories based on the inflammatory component of KC.
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Affiliation(s)
- Gözde Aksoy Aydemir
- Ophthalmology Department, Adıyaman University Training and Research Hospital, 02100, Adıyaman, Turkey.
| | | | - Emre Aydemir
- Ophthalmology Department, Adıyaman University Training and Research Hospital, 02100, Adıyaman, Turkey
| | - Alper Halil Bayat
- Ophthalmology Department, Bahcesehir University Medical Park Goztepe Hospital, Istanbul, Turkey
| | - Serife Sule Cınar
- Ophthalmology Department, Agrı Training and Research Hospital, Agrı, Turkey
| | - Ayse Sevgi Karadağ
- Ophthalmology Department, Adıyaman University Training and Research Hospital, 02100, Adıyaman, Turkey
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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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Zhao Y, Yang H, Li Y, Wang Y, Han X, Zhu Y, Zhang Y, Huang G. Quantitative Assessment of Biomechanical Properties of the Human Keratoconus Cornea Using Acoustic Radiation Force Optical Coherence Elastography. Transl Vis Sci Technol 2022; 11:4. [PMID: 35666497 PMCID: PMC9185997 DOI: 10.1167/tvst.11.6.4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose Quantification of biomechanical properties of keratoconus (KC) corneas has great significance for early diagnosis and treatment of KC, but the corresponding clinical measurement remains challenging. Here, we developed an acoustic radiation force (ARF) optical coherence elastography technique and explored its potential for evaluating biomechanical properties of KC corneas. Methods An ARF system was used to induce the tissue deformation, which was detected by an optical coherence tomography system, and thus the localized point-by-point Young's modulus measurements were achieved. Then, two healthy rabbit eyes were imaged to test the system, after which the human keratoconus cornea was evaluated by using the same method. Three regions were selected for biomechanics analysis: the conical region, the transitional region, and the peripheral region. Results Young's moduli of transitional region ranged from 53.3 to 58.5 kPa. The corresponding values for the peripheral region were determined to be 58.6 kPa and 63.2 kPa, respectively. Young's moduli of the conical region were gradually increased by 18.3% from the center to the periphery, resulting in the minimum and maximum values of 44.9 kPa and 53.1 kPa, respectively. Furthermore, Young's moduli of the anterior and posterior of the center were determined to be 44.9 kPa and 50.7 kPa, respectively. Conclusions Differences in biomechanical properties between the three regions and slight variations within the conical region were clearly distinguished. Biomechanical weakening of the keratoconus cornea was mainly localized in the conical region, especially in the vertex position. Translational Relevance The system may provide a promising clinical tool for the noninvasive evaluation of local corneal biomechanics and thus may have potential applications in early keratoconus detection with further optimization.
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Affiliation(s)
- Yanzhi Zhao
- Nanchang University, Nanchang, P. R. China.,Department of Ophthalmology, The Third Affiliated Hospital of Nanchang University, Nanchang, P. R. China
| | - Hongwei Yang
- Nanchang University, Nanchang, P. R. China.,Department of Ophthalmology, The Third Affiliated Hospital of Nanchang University, Nanchang, P. R. China
| | - Yingjie Li
- Nanchang University, Nanchang, P. R. China.,Department of Ophthalmology, The Third Affiliated Hospital of Nanchang University, Nanchang, P. R. China
| | - Yongbo Wang
- Nanchang University, Nanchang, P. R. China.,Department of Ophthalmology, The Third Affiliated Hospital of Nanchang University, Nanchang, P. R. China
| | - Xiao Han
- Key Laboratory of Opto-Electronic Information Science and Technology of Jiangxi Province and Jiangxi Engineering Laboratory for Optoelectronics Testing Technology, Nanchang Hangkong University, Nanchang, P. R. China
| | - Yirui Zhu
- Key Laboratory of Opto-Electronic Information Science and Technology of Jiangxi Province and Jiangxi Engineering Laboratory for Optoelectronics Testing Technology, Nanchang Hangkong University, Nanchang, P. R. China
| | - Yubao Zhang
- Key Laboratory of Opto-Electronic Information Science and Technology of Jiangxi Province and Jiangxi Engineering Laboratory for Optoelectronics Testing Technology, Nanchang Hangkong University, Nanchang, P. R. China
| | - Guofu Huang
- Nanchang University, Nanchang, P. R. China.,Department of Ophthalmology, The Third Affiliated Hospital of Nanchang University, Nanchang, P. R. China
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Giraudet C, Diaz J, Le Tallec P, Allain JM. Multiscale mechanical model based on patient-specific geometry: Application to early keratoconus development. J Mech Behav Biomed Mater 2022; 129:105121. [DOI: 10.1016/j.jmbbm.2022.105121] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Revised: 01/19/2022] [Accepted: 02/03/2022] [Indexed: 11/30/2022]
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de Barros MRM, Chakravarti S. Pathogenesis of keratoconus: NRF2-antioxidant, extracellular matrix and cellular dysfunctions. Exp Eye Res 2022; 219:109062. [PMID: 35385756 DOI: 10.1016/j.exer.2022.109062] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 03/19/2022] [Accepted: 03/30/2022] [Indexed: 11/04/2022]
Abstract
Keratoconus (KC) is a degenerative disease associated with cell and extracellular matrix (ECM) loss that causes gradual thinning and steepening of the cornea and loss of vision. Collagen cross linking with ultraviolet light treatment can strengthen the ECM and delay weakening of the cornea, but severe cases require corneal transplantation. KC is multifactorial and multigenic, but its pathophysiology is still an enigma. Multiple approaches are being pursued to elucidate the molecular changes that underlie the corneal phenotype to identify relevant genes for tailored candidate searches and to develop potential biomarkers and targets for therapeutic interventions. Recent proteomic and transcriptomic studies suggest dysregulations in oxidative stress, NRF2-regulated antioxidant programs, WNT-signaling, TGF-β, ECM and matrix metalloproteinases. This review aims to provide a broad update on the transcriptomic and proteomic studies of KC with a focus on findings that relate to oxidative stress, and dysregulations in cellular and extracellular matrix functions.
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Affiliation(s)
| | - Shukti Chakravarti
- Department of Ophthalmology, NYU Grossman School of Medicine, NY, 10016, USA; Department of Pathology, NYU Grossman School of Medicine, NY, 10016, USA.
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Simonini I, Annaidh AN, Pandolfi A. Numerical estimation of stress and refractive power maps in healthy and keratoconus eyes. J Mech Behav Biomed Mater 2022; 131:105252. [DOI: 10.1016/j.jmbbm.2022.105252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 04/11/2022] [Accepted: 04/20/2022] [Indexed: 10/18/2022]
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12
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Sun M, Koudouna E, Cogswell D, Avila MY, Koch M, Espana EM. Collagen XII Regulates Corneal Stromal Structure by Modulating Transforming Growth Factor-β Activity. THE AMERICAN JOURNAL OF PATHOLOGY 2022; 192:308-319. [PMID: 34774848 PMCID: PMC8908044 DOI: 10.1016/j.ajpath.2021.10.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Revised: 10/12/2021] [Accepted: 10/19/2021] [Indexed: 02/03/2023]
Abstract
Collagen XII is a regulator of corneal stroma structure and function. The current study examined the role of collagen XII in regulating corneal stromal transforming growth factor (TGF)-β activation and latency. Specifically, with the use of conventional collagen XII null mouse model, the role of collagen XII in the regulation of TGF-β latency and activity in vivo was investigated. Functional quantification of latent TGF-β in stromal matrix was performed by using transformed mink lung reporter cells that produce luciferase as a function of active TGF-β. Col12a1 knockdown with shRNA was used to test the role of collagen XII in TGF-β activation. Col12a1-/- hypertrophic stromata were observed with keratocyte hyperplasia. Increased collagen fibril forward signal was found by second harmonic generation microscopy in the absence of collagen XII. Collagen XII regulated mRNA synthesis of Serpine1, Col1a1, and Col5a1 and deposition of collagens in the extracellular matrix. A functional plasminogen activator inhibitor luciferase assay showed that collagen XII is necessary for latent TGF-β storage in the extracellular matrix and that collagen XII down-regulates active TGF-β. Collagen XII dictates stromal structure and function by regulating TGF-β activity. A hypertrophic phenotype in Col12a1-/- corneal tissue can be explained by abnormal up-regulation of TGF-β activation and decreased latent storage.
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Affiliation(s)
- Mei Sun
- Cornea and External Disease, Department of Ophthalmology, Department of Molecular Pharmacology and Physiology, Tampa, Florida
| | - Elena Koudouna
- Structural Biophysics, School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom
| | - Devon Cogswell
- Cornea and External Disease, Department of Ophthalmology, Department of Molecular Pharmacology and Physiology, Tampa, Florida
| | - Marcel Y. Avila
- Department of Ophthalmology, Universidad Nacional de Colombia, Bogota, Colombia
| | - Manuel Koch
- Institute for Dental Research and Oral Musculoskeletal Biology, Center for Biochemistry, University of Cologne, Cologne, Germany
| | - Edgar M. Espana
- Cornea and External Disease, Department of Ophthalmology, Department of Molecular Pharmacology and Physiology, Tampa, Florida,Morsani College of Medicine, University of South Florida, Tampa, Florida,Address correspondence to Edgar M. Espana, M.D., Ophthalmology, University of South Florida, Morsani College of Medicine, 13330 USF Laurel Dr., 4th Floor, MDC11, Tampa, FL 33612.
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Hao XD, Gao H, Xu WH, Shan C, Liu Y, Zhou ZX, Wang K, Li PF. Systematically Displaying the Pathogenesis of Keratoconus via Multi-Level Related Gene Enrichment-Based Review. Front Med (Lausanne) 2022; 8:770138. [PMID: 35141241 PMCID: PMC8818795 DOI: 10.3389/fmed.2021.770138] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Accepted: 12/31/2021] [Indexed: 01/20/2023] Open
Abstract
Keratoconus (KC) is an etiologically heterogeneous corneal ectatic disorder. To systematically display the pathogenesis of keratoconus (KC), this study reviewed all the reported genes involved in KC, and performed an enrichment analysis of genes identified at the genome, transcription, and protein levels respectively. Combined analysis of multi-level results revealed their shared genes, gene ontology (GO), and pathway terms, to explore the possible pathogenesis of KC. After an initial search, 80 candidate genes, 2,933 transcriptional differential genes, and 947 differential proteins were collected. The candidate genes were significantly enriched in extracellular matrix (ECM) related terms, Wnt signaling pathway and cytokine activities. The enriched GO/pathway terms of transcription and protein levels highlight the importance of ECM, cell adhesion, and inflammatory once again. Combined analysis of multi-levels identified 13 genes, 43 GOs, and 12 pathways. The pathogenic relationships among these overlapping factors maybe as follows. The gene mutations/variants caused insufficient protein dosage or abnormal function, together with environmental stimulation, leading to the related functions and pathways changes in the corneal cells. These included response to the glucocorticoid and reactive oxygen species; regulation of various signaling (P13K-AKT, MAPK and NF-kappaB), apoptosis and aging; upregulation of cytokines and collagen-related enzymes; and downregulation of collagen and other ECM-related proteins. These undoubtedly lead to a reduction of extracellular components and induction of cell apoptosis, resulting in the loosening and thinning of corneal tissue structure. This study, in addition to providing information about the genes involved, also provides an integrated insight into the gene-based etiology and pathogenesis of KC.
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Affiliation(s)
- Xiao-Dan Hao
- Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, College of Medicine, Qingdao University, Qingdao, China
- *Correspondence: Xiao-Dan Hao
| | - Hua Gao
- State Key Laboratory Cultivation Base, Shandong Provincial Key Laboratory of Ophthalmology, Shandong Eye Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Qingdao, China
- Shandong Eye Hospital, Shandong Eye Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China
| | - Wen-Hua Xu
- Department of Inspection, The Medical Faculty of Qingdao University, Qingdao, China
| | - Chan Shan
- Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, College of Medicine, Qingdao University, Qingdao, China
| | - Ying Liu
- Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, College of Medicine, Qingdao University, Qingdao, China
| | - Zhi-Xia Zhou
- Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, College of Medicine, Qingdao University, Qingdao, China
| | - Kun Wang
- Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, College of Medicine, Qingdao University, Qingdao, China
- Kun Wang
| | - Pei-Feng Li
- Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, College of Medicine, Qingdao University, Qingdao, China
- Pei-Feng Li
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Santodomingo-Rubido J, Carracedo G, Suzaki A, Villa-Collar C, Vincent SJ, Wolffsohn JS. Keratoconus: An updated review. Cont Lens Anterior Eye 2022; 45:101559. [PMID: 34991971 DOI: 10.1016/j.clae.2021.101559] [Citation(s) in RCA: 168] [Impact Index Per Article: 84.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 11/23/2021] [Accepted: 12/12/2021] [Indexed: 02/06/2023]
Abstract
Keratoconus is a bilateral and asymmetric disease which results in progressive thinning and steeping of the cornea leading to irregular astigmatism and decreased visual acuity. Traditionally, the condition has been described as a noninflammatory disease; however, more recently it has been associated with ocular inflammation. Keratoconus normally develops in the second and third decades of life and progresses until the fourth decade. The condition affects all ethnicities and both sexes. The prevalence and incidence rates of keratoconus have been estimated to be between 0.2 and 4,790 per 100,000 persons and 1.5 and 25 cases per 100,000 persons/year, respectively, with highest rates typically occurring in 20- to 30-year-olds and Middle Eastern and Asian ethnicities. Progressive stromal thinning, rupture of the anterior limiting membrane, and subsequent ectasia of the central/paracentral cornea are the most commonly observed histopathological findings. A family history of keratoconus, eye rubbing, eczema, asthma, and allergy are risk factors for developing keratoconus. Detecting keratoconus in its earliest stages remains a challenge. Corneal topography is the primary diagnostic tool for keratoconus detection. In incipient cases, however, the use of a single parameter to diagnose keratoconus is insufficient, and in addition to corneal topography, corneal pachymetry and higher order aberration data are now commonly used. Keratoconus severity and progression may be classified based on morphological features and disease evolution, ocular signs, and index-based systems. Keratoconus treatment varies depending on disease severity and progression. Mild cases are typically treated with spectacles, moderate cases with contact lenses, while severe cases that cannot be managed with scleral contact lenses may require corneal surgery. Mild to moderate cases of progressive keratoconus may also be treated surgically, most commonly with corneal cross-linking. This article provides an updated review on the definition, epidemiology, histopathology, aetiology and pathogenesis, clinical features, detection, classification, and management and treatment strategies for keratoconus.
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Affiliation(s)
| | - Gonzalo Carracedo
- Department of Optometry and Vision, Faculty of Optics and Optometry, Universidad Complutense de Madrid, Madrid, Spain
| | - Asaki Suzaki
- Clinical Research and Development Center, Menicon Co., Ltd., Nagoya, Japan
| | - Cesar Villa-Collar
- Department of Pharmacy, Biotechnology, Nutrition, Optics and Optometry, Faculty of Biomedical and Health Sciences, Universidad Europea de Madrid, Madrid, Spain
| | - Stephen J Vincent
- Contact Lens and Visual Optics Laboratory, School of Optometry and Vision Science, Centre for Vision and Eye Research, Queensland University of Technology, Brisbane, Australia
| | - James S Wolffsohn
- School of optometry, Health and Life Sciences, Aston University, Birmingham B4 7ET, United Kingdom
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15
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16
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Almubrad T, Mencucci R, Smedowski A, Samivel R, Almutleb E, Alkanaan A, Khan AA, Masmali A, Akhtar S. Ultrastructural study of collagen fibrils, proteoglycans and lamellae of the cornea treated with iontophoresis - UVA cross-linking and hypotonic riboflavin solution. Saudi J Biol Sci 2021; 28:7160-7174. [PMID: 34867019 PMCID: PMC8626267 DOI: 10.1016/j.sjbs.2021.08.019] [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: 03/25/2021] [Revised: 07/31/2021] [Accepted: 08/03/2021] [Indexed: 11/02/2022] Open
Abstract
To investigate the effects of iontophoresis-ultraviolet A (UVA) cross-linking (CXL) with hypotonic riboflavin solution on the ultrastructural changes in the lamellae, collagen fibrils (CFs), and proteoglycans (PGs) in the central and peripheral stroma of the human corneal buttons. The iontophoresis method was used for the trans-epithelial application of hypotonic riboflavin in ex vivo corneal culture for 5 min. The corneas were irradiated using three methods: Group 1 (G1) , a UVA irradiance of 3 mW/cm2 for 30 min; Group 2 (G2) , a UVA irradiance of 10 mW/cm2 for 9 min; Group 3 (G3) , without UVA irradiation. Three untreated corneas were used as controls ( G0 ). After the CXL procedure, the corneas were processed for electron microscopy. The CF diameter and PGs in each sample were analyzed using the iTEM program. The keratocyte organelles and stromal architecture in the peripheral cornea were better preserved than those in the central cornea. In G1 and G2, the mean CF diameter in the peripheral cornea was significantly higher than that in the central cornea. In G3, the CF diameter in the central cornea was significantly larger than that in the peripheral cornea. Furthermore, differences in PG area size were observed between the central and peripheral corneas in all groups. Riboflavin + UVA application at 3 mW/cm2 for 30 min and 10 mW/cm2 for 9 min was a suitable method of CXL; however, 3 mW/cm2 for 30 min improved the organization and size of the collagen fibrils. CXL treatment applied at the periphery was more effective than that applied at the center.
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Affiliation(s)
- Turki Almubrad
- Cornea Research Chair, Department of Optics and Vision Sciences, College of Applied Medical Science, King Saud University, Riyadh, Saudi Arabia
| | - Rita Mencucci
- Department of Oto-Neuro-Ophthalmology Surgical Sciences, Eye Clinic, University of Florence, Italy
| | - Adrian Smedowski
- Department of Physiology, Faculty of Medical Sciences in Katowice, Medical University of Silesia, Katowice, Poland.,Department of Oto-Neuro-Ophthalmology Surgical Sciences, Eye Clinic, University of Florence, Italy
| | - Ramachandran Samivel
- Cornea Research Chair, Department of Optics and Vision Sciences, College of Applied Medical Science, King Saud University, Riyadh, Saudi Arabia
| | - Essam Almutleb
- Cornea Research Chair, Department of Optics and Vision Sciences, College of Applied Medical Science, King Saud University, Riyadh, Saudi Arabia
| | - Aljoharah Alkanaan
- Cornea Research Chair, Department of Optics and Vision Sciences, College of Applied Medical Science, King Saud University, Riyadh, Saudi Arabia
| | - Adnan Ali Khan
- Cornea Research Chair, Department of Optics and Vision Sciences, College of Applied Medical Science, King Saud University, Riyadh, Saudi Arabia
| | - Ali Masmali
- Cornea Research Chair, Department of Optics and Vision Sciences, College of Applied Medical Science, King Saud University, Riyadh, Saudi Arabia
| | - Saeed Akhtar
- Cornea Research Chair, Department of Optics and Vision Sciences, College of Applied Medical Science, King Saud University, Riyadh, Saudi Arabia
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Raoux C, Schmeltz M, Bied M, Alnawaiseh M, Hansen U, Latour G, Schanne-Klein MC. Quantitative structural imaging of keratoconic corneas using polarization-resolved SHG microscopy. BIOMEDICAL OPTICS EXPRESS 2021; 12:4163-4178. [PMID: 34457406 PMCID: PMC8367248 DOI: 10.1364/boe.426145] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 04/29/2021] [Accepted: 05/22/2021] [Indexed: 05/20/2023]
Abstract
The human cornea is mainly composed of collagen fibrils aligned together within stacked lamellae. This lamellar structure can be affected in pathologies such as keratoconus, which is characterized by progressive corneal thinning and local steepening. In this study, we use polarization-resolved second harmonic generation (P-SHG) microscopy to characterize 8 control and 6 keratoconic human corneas. Automated processing of P-SHG images of transverse sections provides the collagen orientation in every pixel with sub-micrometer resolution. Series of P-SHG images recorded in the most anterior region of the stroma evidence sutural lamellae inclined at 22° ± 5° to the corneal surface, but show no significant difference between control and keratoconic corneas. In contrast, series of P-SHG images acquired along the full thickness of the stroma show a loss of order in the lamellar structure of keratoconic corneas, in agreement with their defective mechanical properties. This structural difference is analyzed quantitatively by computing the entropy and the orientation index of the collagen orientation distribution and significant differences are obtained along the full thickness of the stroma. This study shows that P-SHG is an effective tool for automatic quantitative analysis of structural defects of human corneas and should be applied to other collagen-rich tissues.
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Affiliation(s)
- Clothilde Raoux
- Laboratory for Optics and Biosciences, Ecole polytechnique, CNRS, INSERM, Institut Polytechnique de Paris, 91128 Palaiseau, France
- These authors contributed equally
| | - Margaux Schmeltz
- Laboratory for Optics and Biosciences, Ecole polytechnique, CNRS, INSERM, Institut Polytechnique de Paris, 91128 Palaiseau, France
- These authors contributed equally
| | - Marion Bied
- Laboratory for Optics and Biosciences, Ecole polytechnique, CNRS, INSERM, Institut Polytechnique de Paris, 91128 Palaiseau, France
| | - Maged Alnawaiseh
- Department of Ophthalmology, Hospital Fulda, University of Marburg, Campus Fulda, 36043 Fulda, Germany
| | - Uwe Hansen
- Institute for Musculoskeletal Medicine, University Hospital Münster, 48149 Münster, Germany
| | - Gaël Latour
- Laboratory for Optics and Biosciences, Ecole polytechnique, CNRS, INSERM, Institut Polytechnique de Paris, 91128 Palaiseau, France
- Université Paris-Saclay, 91190 Saint-Aubin, France
| | - Marie-Claire Schanne-Klein
- Laboratory for Optics and Biosciences, Ecole polytechnique, CNRS, INSERM, Institut Polytechnique de Paris, 91128 Palaiseau, France
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18
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Haneef A, Giridhara Gopalan RO, Rajendran DT, Nunes J, Kuppamuthu D, Radhakrishnan N, Young TH, Hsieh HY, Prajna NV, Willoughby CE, Williams R. Chemical Cross-Linking of Corneal Tissue to Reduce Progression of Loss of Sight in Patients With Keratoconus. Transl Vis Sci Technol 2021; 10:6. [PMID: 34003973 PMCID: PMC8088226 DOI: 10.1167/tvst.10.5.6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose We aimed to develop a novel chemical cross-linker treatment for keratoconus by reacting dicarboxylic acid spacer molecules and amine functional groups on protein structure of the tissue using carbodi-imide chemistry. We propose this as an alternative to conventional cross-linking treatment for keratoconus. Methods The study involved optimization of the cross-linker formulation. Mechanical stiffness of ex vivo porcine and human corneas after application of the cross-linker was measured. Histochemical analysis was performed to record changes in gross morphology after cross-linker treatment on ex vivo porcine and human and in vivo rabbit corneas. Terminal deoxynucleotidyl transferase-mediated dUTP-X nick-end-labeling (TUNEL) staining was performed to study apoptotic effects of cross-linker. Cytotoxicity potential of cross-linker was evaluated by studying explant cultures for cellular outgrowth and immunostaining assays on porcine and human corneas after treatment. Results We demonstrated a clinically relevant increase in stiffness in ex vivo experiments using porcine and human cornea without removal of corneal epithelium. Histological analysis showed no change in gross morphology of cornea and no evidence of apoptosis. In vivo treatment of rabbit eyes demonstrated initial thinning of corneal epithelium that recovered after seven days although with abnormal regularity of cells. Cellular outgrowth from corneal explant cultures after treatment further confirmed cell survival after treatment. Conclusions This chemical cross-linking of corneal tissue has potential advantages over current therapeutic options including lower cytotoxicity to stromal cells than ultraviolet A treatment. Translational Relevance The cross-linker has potential to become a treatment for keratoconus because it overcomes the need for procedures using specialized equipment and ensures accessibility to large populations.
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Affiliation(s)
- Atikah Haneef
- Department of Eye and Vision Science, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK
| | | | | | - Jessica Nunes
- Aravind Medical Research Foundation, Madurai, Tamil Nadu, India
| | | | | | - Tai-Horng Young
- Department of Biomedical Engineering, National Taiwan University, Taipei, Taiwan
| | - Hao-Ying Hsieh
- Department of Biomedical Engineering, National Taiwan University, Taipei, Taiwan
| | | | - Colin E Willoughby
- Department of Eye and Vision Science, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK
| | - Rachel Williams
- Department of Eye and Vision Science, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK
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Cheung IM, Mcghee CN, Sherwin T. A new perspective on the pathobiology of keratoconus: interplay of stromal wound healing and reactive species‐associated processes. Clin Exp Optom 2021; 96:188-96. [DOI: 10.1111/cxo.12025] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Accepted: 10/30/2012] [Indexed: 12/13/2022] Open
Affiliation(s)
- Isabella My Cheung
- Department of Ophthalmology, New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand,
| | - Charles Nj Mcghee
- Department of Ophthalmology, New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand,
| | - Trevor Sherwin
- Department of Ophthalmology, New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand,
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20
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Ng SM, Ren M, Lindsley KB, Hawkins BS, Kuo IC. Transepithelial versus epithelium-off corneal crosslinking for progressive keratoconus. Cochrane Database Syst Rev 2021; 3:CD013512. [PMID: 33765359 PMCID: PMC8094622 DOI: 10.1002/14651858.cd013512.pub2] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
BACKGROUND Keratoconus is the most common corneal dystrophy. It can cause loss of uncorrected and best-corrected visual acuity through ectasia (thinning) of the central or paracentral cornea, irregular corneal scarring, or corneal perforation. Disease onset usually occurs in the second to fourth decade of life, periods of peak educational attainment or career development. The condition is lifelong and sight-threatening. Corneal collagen crosslinking (CXL) using ultraviolet A (UVA) light applied to the cornea is the only treatment that has been shown to slow progression of disease. The original, more widely known technique involves application of UVA light to de-epithelialized cornea, to which a photosensitizer (riboflavin) is added topically throughout the irradiation process. Transepithelial CXL is a recently advocated alternative to the standard CXL procedure, in that the epithelium is kept intact during CXL. Retention of the epithelium offers the putative advantages of faster healing, less patient discomfort, faster visual rehabilitation, and less risk of corneal haze. OBJECTIVES To assess the short- and long-term effectiveness and safety of transepithelial CXL compared with epithelium-off CXL for progressive keratoconus. SEARCH METHODS To identify potentially eligible studies, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2020, Issue 1); Ovid MEDLINE; Embase.com; PubMed; Latin American and Caribbean Health Sciences Literature database (LILACS); ClinicalTrials.gov; and World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We did not impose any date or language restrictions. We last searched the electronic databases on 15 January 2020. SELECTION CRITERIA We included randomized controlled trials (RCTs) in which transepithelial CXL had been compared with epithelium-off CXL in participants with progressive keratoconus. DATA COLLECTION AND ANALYSIS We used standard Cochrane methodology. MAIN RESULTS We included 13 studies with 723 eyes of 578 participants enrolled; 13 to 119 participants were enrolled per study. Seven studies were conducted in Europe, three in the Middle East, and one each in India, Russia, and Turkey. Seven studies were parallel-group RCTs, one study was an RCT with a paired-eyes design, and five studies were RCTs in which both eyes of some or all participants were assigned to the same intervention. Eleven studies compared transepithelial CXL with epithelium-off CXL in participants with progressive keratoconus. There was no evidence of an important difference between intervention groups in maximum keratometry (denoted 'maximum K' or 'Kmax'; also known as steepest keratometry measurement) at 12 months or later (mean difference (MD) 0.99 diopters (D), 95% CI -0.11 to 2.09; 5 studies; 177 eyes; I2 = 41%; very low certainty evidence). Few studies described other outcomes of interest. The evidence is very uncertain that epithelium-off CXL may have a small (data from two studies were not pooled due to considerable heterogeneity (I2 = 92%)) or no effect on stabilization of progressive keratoconus compared with transepithelial CXL; comparison of the estimated proportions of eyes with decreases or increases of 2 or more diopters in maximum K at 12 months from one study with 61 eyes was RR 0.32 (95% CI 0.09 to 1.12) and RR (non-event) 0.86 (95% CI 0.74 to 1.00), respectively (very low certainty). We did not estimate an overall effect on corrected-distance visual acuity (CDVA) because substantial heterogeneity was detected (I2 = 70%). No study evaluated CDVA gain or loss of 10 or more letters on a logarithm of the minimum angle of resolution (logMAR) chart. Transepithelial CXL may result in little to no difference in CDVA at 12 months or beyond. Four studies reported that either no adverse events or no serious adverse events had been observed. Another study noted no change in endothelial cell count after either procedure. Moderate certainty evidence from 4 studies (221 eyes) found that epithelium-off CXL resulted in a slight increase in corneal haze or scarring when compared to transepithelial CXL (RR (non-event) 1.07, 95% CI 1.01 to 1.14). Three studies, one of which had three arms, compared outcomes among participants assigned to transepithelial CXL using iontophoresis versus those assigned to epithelium-off CXL. No conclusive evidence was found for either keratometry or visual acuity outcomes at 12 months or later after surgery. Low certainty evidence suggests that transepithelial CXL using iontophoresis results in no difference in logMAR CDVA (MD 0.00 letter, 95% CI -0.04 to 0.04; 2 studies; 51 eyes). Only one study examined gain or loss of 10 or more logMAR letters. In terms of adverse events, one case of subepithelial infiltrate was reported after transepithelial CXL with iontophoresis, whereas two cases of faint corneal scars and four cases of permanent haze were observed after epithelium-off CXL. Vogt's striae were found in one eye after each intervention. The certainty of the evidence was low or very low for the outcomes in this comparison due to imprecision of estimates for all outcomes and risk of bias in the studies from which data have been reported. AUTHORS' CONCLUSIONS Because of lack of precision, frequent indeterminate risk of bias due to inadequate reporting, and inconsistency in outcomes measured and reported among studies in this systematic review, it remains unknown whether transepithelial CXL, or any other approach, may confer an advantage over epithelium-off CXL for patients with progressive keratoconus with respect to further progression of keratoconus, visual acuity outcomes, and patient-reported outcomes (PROs). Arrest of the progression of keratoconus should be the primary outcome of interest in future trials of CXL, particularly when comparing the effectiveness of different approaches to CXL. Furthermore, methods of assessing and defining progressive keratoconus should be standardized. Trials with longer follow-up are required in order to assure that outcomes are measured after corneal wound-healing and stabilization of keratoconus. In addition, perioperative, intraoperative, and postoperative care should be standardized to permit meaningful comparisons of CXL methods. Methods to increase penetration of riboflavin through intact epithelium as well as delivery of increased dose of UVA may be needed to improve outcomes. PROs should be measured and reported. The visual significance of adverse outcomes, such as corneal haze, should be assessed and correlated with other outcomes, including PROs.
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Affiliation(s)
- Sueko M Ng
- Department of Ophthalmology, School of Medicine, University of Colorado, Aurora, CO, USA
| | - Mark Ren
- Wilmer Eye Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Kristina B Lindsley
- Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, Netherlands
| | - Barbara S Hawkins
- Wilmer Eye Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Irene C Kuo
- Wilmer Eye Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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21
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Liu T, Shen M, Li H, Zhang Y, Mu B, Zhao X, Wang Y. Changes and quantitative characterization of hyper-viscoelastic biomechanical properties for young corneal stroma after standard corneal cross-linking treatment with different ultraviolet-A energies. Acta Biomater 2020; 113:438-451. [PMID: 32525050 DOI: 10.1016/j.actbio.2020.06.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 05/30/2020] [Accepted: 06/02/2020] [Indexed: 12/27/2022]
Abstract
Corneal collagen cross-linking (CXL) treatment can restore vision in patients suffering from keratoconus and corneal injury, by improving the mechanical properties of the cornea. The correlation between ultraviolet-A (UVA) irradiant energies of standard CXL (SCXL) and corneal visco-hyperelastic mechanical behavior remains unknown. In this study, SCXL with four different UVA irradiant energy doses (0-5.4 J/cm2) were administered as part of quantitative treatments of corneal stromal lenticules extracted from young myopic patients via small incision lenticule extraction (SMILE) corneal refractive surgery. Double-strip samples with symmetric geometries were cut simultaneously for SCXL treatment and non-treated control. First, 40 pairs of strips were loaded to failure to assess the mechanical parameters of the material. Then, another 40 pairs were tested using a special uniaxial tensile test including quasi-static loading-unloading, instantaneous loading, and stress relaxation, to determine the visco-hyperelastic mechanical behavior. Upon combining the collagen fibril crimping constitutive model with the quasi-linear viscoelastic model, it was observed that with increasing UVA energy dose, the corneal strength and hyperelastic stiffness were significantly enhanced, while the maximum stretch and viscosity of the cornea were significantly reduced. Considering the quantitative analysis of SCXL and the rehabilitation prediction of keratoconus treatment, the results clarify the biomechanical behavior of human corneal stroma in SCXL clinical surgery. STATEMENT OF SIGNIFICANCE: This study quantitatively analyzes the improvement in the biomechanical properties of young central corneal stroma, due to SCXL treatment with different energies. Furthermore, the correlation between the hyper-viscoelastic mechanical parameters and UVA irradiant energy doses of SCXL are clarified. The contribution of this study fills the knowledge gap of the CXL on corneal biomechanics. It can not only clarify this mechanism better but also assist with guiding SCXL surgery for individualized patient corneas.
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Affiliation(s)
- 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, Shanghai 200240, China
| | - Min Shen
- Department of Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin 300350 China.
| | - Hongxun Li
- Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin 300020 China; Clinical College of Ophthalmology, Tianjin Medical University, Tianjin 300070 China
| | - Yan Zhang
- Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin 300020 China; Clinical College of Ophthalmology, Tianjin Medical University, Tianjin 300070 China
| | - Bokun Mu
- Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin 300020 China; Clinical College of Ophthalmology, Tianjin Medical University, Tianjin 300070 China
| | - Xinheng Zhao
- Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin 300020 China; Clinical College of Ophthalmology, Tianjin Medical University, Tianjin 300070 China
| | - Yan Wang
- Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin 300020 China; Clinical College of Ophthalmology, Tianjin Medical University, Tianjin 300070 China
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22
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Intrastromal implantation of chicken corneal grafts into the cornea of rabbits for corneal thickening: an experimental study. Int Ophthalmol 2020; 41:243-255. [PMID: 32845463 DOI: 10.1007/s10792-020-01573-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 08/17/2020] [Indexed: 10/23/2022]
Abstract
PURPOSE To evaluate the feasibility and effects of the intrastromal implantation of chemically modified corneal stroma obtained from chicken into the corneas of rabbits for corneal thickening. METHODS Chicken corneas were cut, debrided, treated with cross-linking and implanted in an intrastromal pouch created in the cornea of 10 white New Zealand rabbits with femtosecond laser. Slit-lamp biomicroscopy and optical coherence tomography were performed immediately, 7, 30 and 90 days postoperatively. Corneas were removed at 90 days and cut in two halves. One half was sent to histological analysis for the presence of necrosis, polymorphonuclear inflammatory cells, blood vessels and fibrosis, while the other half was evaluated with transmission electron microscopy to verify tissue organization and the presence of keratocytes and inflammatory cells. Corneal thicknesses were comparatively analyzed over time with Wilcoxon test (p ≤ 0.05). RESULTS The chicken grafts were incorporated into the cornea of all animals over time. Mean rabbit cornea thickness increased from 338 µm preoperatively to 538 µm (p < 0.0077) at 90 days, while mean chicken graft thickness decreased from 350 to 215 µm (p < 0.0077). No clear signs of rejection attributable to the xenograft were observed in any of the implanted eyes. However, some macroscopic and histological events were observed in some of the eyes, probably due to procedural issues during implantation. CONCLUSION The intrastromal implantation of chicken grafts was shown to be feasible and predictable to thicken the recipient rabbit cornea without apparent rejection. However, before being considered in humans, further meticulous clinical trials are required to establish the clinical utility, safety and efficacy of xenografts for the treatment of patients with advanced keratoconus.
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23
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Hayes S, Aldahlawi N, Marcovich AL, Brekelmans J, Goz A, Scherz A, Young RD, Bell JS, O'Brart DP, Nuijts RMMA, Meek KM. The effect of bacteriochlorophyll derivative WST-D and near infrared light on the molecular and fibrillar architecture of the corneal stroma. Sci Rep 2020; 10:9836. [PMID: 32555309 PMCID: PMC7299946 DOI: 10.1038/s41598-020-66869-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 05/28/2020] [Indexed: 11/30/2022] Open
Abstract
A cross-linking technique involving application of Bacteriochlorophyll Derivative WST-11 mixed with dextran (WST-D) to the epithelium-debrided cornea and illumination with Near Infrared (NIR), has been identified as a promising therapy for stiffening pathologically weakened corneas. To investigate its effect on corneal collagen architecture, x-ray scattering and electron microscopy data were collected from paired WST-D/NIR treated and untreated rabbit corneas. The treated eye received 2.5 mg/mL WST-D and was illuminated by a NIR diode laser (755 nm, 10 mW/cm2). An increase in corneal thickness (caused by corneal oedema) occurred at 1-day post-treatment but resolved in the majority of cases within 4 days. The epithelium was fully healed after 6–8 days. X-ray scattering revealed no difference in average collagen interfibrillar spacing, fibril diameter, D-periodicity or intermolecular spacing between treated and untreated specimens. Similarly, electron microscopy images of the anterior and posterior stroma in healed WST-D/NIR corneas and untreated controls revealed no obvious differences in collagen organisation or fibril diameter. As the size and organisation of stromal collagen is closely associated with the optical properties of the cornea, the absence of any large-scale changes following treatment confirms the potential of WST-D/NIR therapy as a means of safely stiffening the cornea.
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Affiliation(s)
- S Hayes
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom.
| | - N Aldahlawi
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom
| | - A L Marcovich
- Department of Plant and Environmental Sciences, The Weizmann Institute of Science, Rehovot, Israel.,Department of Ophthalmology, Kaplan Medical Center, Rehovot, Israel
| | - J Brekelmans
- Department of Plant and Environmental Sciences, The Weizmann Institute of Science, Rehovot, Israel.,University Eye Clinic Maastricht, Maastricht University Medical Center, Maastricht, the Netherlands
| | - A Goz
- Department of Plant and Environmental Sciences, The Weizmann Institute of Science, Rehovot, Israel.,Department of Ophthalmology, Kaplan Medical Center, Rehovot, Israel
| | - A Scherz
- Department of Plant and Environmental Sciences, The Weizmann Institute of Science, Rehovot, Israel
| | - R D Young
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom
| | - J S Bell
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom
| | - D P O'Brart
- Keratoconus Research Institute, Department of Ophthalmology, St Thomas Hospital, London, United Kingdom
| | - R M M A Nuijts
- University Eye Clinic Maastricht, Maastricht University Medical Center, Maastricht, the Netherlands
| | - K M Meek
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom
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De Stefano VS, Ford MR, Seven I, Dupps WJ. Depth-Dependent Corneal Biomechanical Properties in Normal and Keratoconic Subjects by Optical Coherence Elastography. Transl Vis Sci Technol 2020; 9:4. [PMID: 32832211 PMCID: PMC7414661 DOI: 10.1167/tvst.9.7.4] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Accepted: 04/07/2020] [Indexed: 12/15/2022] Open
Abstract
Purpose Compare depth-resolved biomechanical properties in normal and keratoconic corneas in live human subjects using optical coherence elastography (OCE). Methods In a prospective series of normal and keratoconus (KC) eyes, a corneal perturbation was applied by a custom swept-source OCE system using a transparent flat lens coupled to force transducers. Cross-correlation was applied to track frame-by-frame OCT speckle displacement. Regional displacements for the anterior and posterior stroma were plotted in force versus displacement (k) graphs. A spatial biomechanical property ratio (ka/kp ) was defined by dividing the maximum total displacement by the maximum force for the anterior (ka ) and posterior cornea (kp) and was compared between normal and KC groups with the Mann-Whitney U test. Area under the receiver operating characteristics curve (AUROC) for differentiating normal and KC eyes was calculated for ka/kp , kmax, and thinnest point of corneal thickness (TPCT). Results Thirty-six eyes were analyzed (21 eyes of 12 normal subjects and 15 KC eyes of 12 subjects). The ka/kp for the normal group was 1.135 ± 0.07 (mean ± standard deviation) and 1.02 ± 0.08 for the KC group (P < 0.001), indicating a relative deficit in anterior stromal stiffness in KC eyes. AUROC was 0.91 for ka /kp , 0.95 for kmax, and 1 for TPCT. Conclusions Significant differences in depth-dependent corneal biomechanical properties were observed between normal and KC subjects. Translational Relevance OCE was applied for the first time to human KC subjects and revealed alterations in the normal anterior-to-posterior stromal stiffness gradient, a novel and clinically accessible disease biomarker.
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Affiliation(s)
- Vinicius S De Stefano
- Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA.,Department of Ophthalmology and Visual Sciences, Federal University of Sao Paulo, Sao Paulo, Brazil
| | - Matthew R Ford
- Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Ibrahim Seven
- Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
| | - William J Dupps
- Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA.,Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.,Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH, USA
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25
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Anisimova NS, Anisimov SI, Shilova NF, Zemskaya AY, Gavrilova NA, Anisimova SY. [Ultraviolet crosslinking in the treatment of keratoconus in patients with thin corneas]. Vestn Oftalmol 2020; 136:99-106. [PMID: 32366077 DOI: 10.17116/oftalma202013602199] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Corneal collagen cross-linking (CXL) is a procedure that aims to halt the progression of corneal ectasia in keratoconic eyes. It is achieved by inducing cross-links in the corneal stroma and extracellular matrix by exposing it to ultraviolet-A (370 nm) irradiation while it is filled with photosensitizer (riboflavin). According to the conventional protocol, the recommended de-epithelialized corneal thickness should be higher than 400 μm in order to avoid radiation damage to the corneal endothelium. However, in progressive keratoconus, corneal thickness is often close to or lower than this threshold of 400 μm, which limits the application of cross-linking for these patients. The present article reviews the different protocols of cross-linking for thin corneas, their advantages and disadvantages. At present, clinical research on modified cross-linking protocols is still limited due to the methodology and a low number of patients involved. Thus, comparative randomized controlled studies with long-term follow-up are necessary to confirm the safety and effectiveness of several CXL protocols and identify the most efficient one.
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Affiliation(s)
- N S Anisimova
- Eye Center Vostok-Prozrenie, Moscow, Russia.,A.I. Yevdokimov Moscow State University of Medicine and Dentristy, Moscow, Russia
| | - S I Anisimov
- Eye Center Vostok-Prozrenie, Moscow, Russia.,A.I. Yevdokimov Moscow State University of Medicine and Dentristy, Moscow, Russia
| | | | - A Yu Zemskaya
- A.I. Yevdokimov Moscow State University of Medicine and Dentristy, Moscow, Russia
| | - N A Gavrilova
- A.I. Yevdokimov Moscow State University of Medicine and Dentristy, Moscow, Russia
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26
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Kujawski S, Crespo C, Luz M, Yuan M, Winkler S, Knust E. Loss of Crb2b-lf leads to anterior segment defects in old zebrafish. Biol Open 2020; 9:bio047555. [PMID: 31988089 PMCID: PMC7044448 DOI: 10.1242/bio.047555] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Accepted: 01/09/2020] [Indexed: 12/02/2022] Open
Abstract
Defects in the retina or the anterior segment of the eye lead to compromised vision and affect millions of people. Understanding how these ocular structures develop and are maintained is therefore of paramount importance. The maintenance of proper vision depends, among other factors, on the function of genes controlling apico-basal polarity. In fact, mutations in polarity genes are linked to retinal degeneration in several species, including human. Here we describe a novel zebrafish crb2b allele (crb2be40 ), which specifically affects the crb2b long isoform. crb2be40 mutants are viable and display normal ocular development. However, old crb2be40 mutant fish develop multiple defects in structures of the anterior segment, which includes the cornea, the iris and the lens. Phenotypes are characterised by smaller pupils due to expansion of the iris and tissues of the iridocorneal angle, an increased number of corneal stromal keratocytes, an abnormal corneal endothelium and an expanded lens capsule. These findings illustrate a novel role for crb2b in the maintenance of the anterior segment and hence add an important function to this polarity regulator, which may be conserved in other vertebrates including humans.
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Affiliation(s)
- Satu Kujawski
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Cátia Crespo
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Marta Luz
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Michaela Yuan
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Sylke Winkler
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Elisabeth Knust
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
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27
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Kuo IC, Hawkins BS, Ren M, Lindsley KB. Transepithelial versus epithelium-off corneal crosslinking for progressive keratoconus. Hippokratia 2020. [DOI: 10.1002/14651858.cd013512] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Irene C Kuo
- Wilmer Eye Institute, The Johns Hopkins University School of Medicine; Department of Ophthalmology; 4924 Campbell Blvd #100 Baltimore Maryland USA 21236
| | - Barbara S Hawkins
- The Johns Hopkins University School of Medicine; Wilmer Eye Institute; 550 North Broadway, 9th floor Baltimore Maryland USA 21205-2010
| | - Mark Ren
- The Johns Hopkins University School of Medicine; Wilmer Eye Institute; 550 North Broadway, 9th floor Baltimore Maryland USA 21205-2010
| | - Kristina B Lindsley
- IBM Watson Health; Life Sciences, Oncology, & Genomics; Baltimore Maryland USA
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28
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Alkanaan A, Barsotti R, Kirat O, Khan A, Almubrad T, Akhtar S. Collagen fibrils and proteoglycans of peripheral and central stroma of the keratoconus cornea - Ultrastructure and 3D transmission electron tomography. Sci Rep 2019; 9:19963. [PMID: 31882786 PMCID: PMC6934547 DOI: 10.1038/s41598-019-56529-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Accepted: 12/05/2019] [Indexed: 02/04/2023] Open
Abstract
Keratoconus (KC) is a progressive corneal disorder in which vision gradually deteriorates as a result of continuous conical protrusion and the consequent altered corneal curvature. While the majority of the literature focus on assessing the center of this diseased cornea, there is growing evidence of peripheral involvement in the disease process. Thus, we investigated the organization of collagen fibrils (CFs) and proteoglycans (PGs) in the periphery and center of KC corneal stroma. Three-dimensional transmission electron tomography on four KC corneas showed the degeneration of microfibrils within the CFs and disturbance in the attachment of the PGs. Within the KC corneas, the mean CF diameter of the central-anterior stroma was significantly (p ˂ 0.001) larger than the peripheral-anterior stroma. The interfibrillar distance of CF was significantly (p ˂ 0.001) smaller in the central stroma than in the peripheral stroma. PGs area and the density in the central KC stroma were larger than those in the peripheral stroma. Results of the current study revealed that in the pre- Descemet's membrane stroma of the periphery, the degenerated CFs and PGs constitute biomechanically weak lamellae which are prone to disorganization and this suggests that the peripheral stroma plays an important role in the pathogenicity of the KC cornea.
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Affiliation(s)
- Aljoharah Alkanaan
- Cornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia
| | - Robert Barsotti
- Department of Biomedical Sciences, Philadelphia college of Osteopathic Medicine, Philadelphia, PA, USA
| | - Omar Kirat
- Department of Ophthalmology, King Khalid Eye Specialist Hospital, Riyadh, Saudi Arabia
| | - Adnan Khan
- Cornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia
| | - Turki Almubrad
- Cornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia
| | - Saeed Akhtar
- Cornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia.
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Tissue-Derived Biological Particles Restore Cornea Properties in an Enzyme-Mediated Corneal Ectatic Model. Bioengineering (Basel) 2019; 6:bioengineering6040090. [PMID: 31569699 PMCID: PMC6956048 DOI: 10.3390/bioengineering6040090] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Revised: 09/18/2019] [Accepted: 09/24/2019] [Indexed: 01/30/2023] Open
Abstract
Purpose: To investigate the impact of tissue derived biological particles on enzyme-mediated weakened corneas. Methods: Rabbit corneas were treated with enzymes to create an ex vivo ectatic model that simulated representative characteristics of keratoconus (KC). Porcine cornea, cartilage, and lymph node tissues were processed to remove most cellular components and cryomilled into microparticles. The KC corneas were cultured in medium containing the tissue-derived biological particles (TDP) overnight. The mechanical, thermal, ultrastructural changes, and gene expressions of corneal stromal cells were characterized to evaluate the effects of the TDP treatment. Results: The enzyme treatment significantly reduced corneal mechanics and thermal stability, and also disrupted the extracellular matrix ultrastructure. After culturing with TDP medium, the Young’s modulus of the modeled KC corneas increased by ~50%, comparable to normal cornea controls. Similarly, the thermal denaturation temperature of the corneas was restored. These findings also corresponded to a significant increase in collagen fibril density after TDP treatment. Furthermore, corneas cultured in TDP medium significantly downregulated expression of the pro-inflammatory gene Tnfα, and restored the expression of the key keratocyte markers Aldh, keratocan, and biglycan. Conclusions: Tissue-derived biological particles reinforce mechanical and thermal properties of corneal tissue in an ex vivo model of KC. Through this study, we demonstrate and characterize the previously unexplored impact of tissue-derived biological scaffolds on corneal biomechanics, thermal stability, and gene expression, presenting a potential new therapy for ocular disease.
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30
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Choroidal thickness in keratoconus. Int Ophthalmol 2019; 40:135-140. [PMID: 31432355 DOI: 10.1007/s10792-019-01156-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Revised: 06/22/2019] [Accepted: 08/14/2019] [Indexed: 10/26/2022]
Abstract
PURPOSE Keratoconus is an ectatic eye disease characterized by progressive thinning and steepening of the cornea which leads to irregular astigmatism and visual function loss. Determination of choroidal thickness in keratoconus patients may help us to better understand and manage the keratoconus disease. Choroidal thickness may be a potential marker for disease activity in keratoconus patients. In this study, we aimed to determine choroidal thickness in keratoconus patients and compare the results with the age-matched control group. METHODS This is a prospective study with a control group. Keratometry and thinnest corneal thickness was measured and recorded in keratoconus patients. Choroidal thickness of all subjects was measured using an optical coherence tomography device (Spectralis OCT, version 6.0, Heidelberg Engineering, Germany) with an enhanced depth imaging mode without pupil dilation. Mean choroidal thickness of keratoconus patients was compared with healthy subjects. RESULTS One hundred and sixty eyes of 80 healthy subjects and 160 eyes of 80 keratoconus patients were included in the study. Mean thinnest corneal thickness of the keratoconus patients was 449.7 ± 3.2 microns. Mean corneal keratometry value and cylindrical refraction error in the keratoconus patients were 53.2 ± 0.2 and 3.3 ± 0.1 diopters, respectively. Mean choroidal thickness was 363.9 ± 59.8 and 328.4 ± 67.2 microns in keratoconus patients and healthy subjects, respectively. There was a very significant difference between keratoconus patients and healthy subjects in terms of choroidal thickness (P = 0.000). There was not a statistically significant correlation between choroidal thickness and thinnest corneal thickness in keratoconus patients (P = 0.814). CONCLUSION Choroidal thickness was found to be increased in keratoconus patients. Choroidal thickness could potentially become a new clinical marker for disease activity in keratoconus patients.
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31
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Blackburn BJ, Jenkins MW, Rollins AM, Dupps WJ. A Review of Structural and Biomechanical Changes in the Cornea in Aging, Disease, and Photochemical Crosslinking. Front Bioeng Biotechnol 2019; 7:66. [PMID: 31019909 PMCID: PMC6459081 DOI: 10.3389/fbioe.2019.00066] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Accepted: 03/07/2019] [Indexed: 12/27/2022] Open
Abstract
The study of corneal biomechanics is motivated by the tight relationship between biomechanical properties and visual function within the ocular system. For instance, variation in collagen fibril alignment and non-enzymatic crosslinks rank high among structural factors which give rise to the cornea's particular shape and ability to properly focus light. Gradation in these and other factors engender biomechanical changes which can be quantified by a wide variety of techniques. This review summarizes what is known about both the changes in corneal structure and associated changes in corneal biomechanical properties in aging, keratoconic, and photochemically crosslinked corneas. In addition, methods for measuring corneal biomechanics are discussed and the topics are related to both clinical studies and biomechanical modeling simulations.
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Affiliation(s)
- Brecken J. Blackburn
- Cole Eye Institute, Cleveland Clinic, Cleveland, OH, United States
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States
- Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of CWRU, Cleveland, OH, United States
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States
| | - Michael W. Jenkins
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States
- Department of Pediatrics, Case Western Reserve University, Cleveland, OH, United States
| | - Andrew M. Rollins
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States
| | - William J. Dupps
- Cole Eye Institute, Cleveland Clinic, Cleveland, OH, United States
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States
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Differential epithelial and stromal protein profiles in cone and non-cone regions of keratoconus corneas. Sci Rep 2019; 9:2965. [PMID: 30814630 PMCID: PMC6393548 DOI: 10.1038/s41598-019-39182-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Accepted: 01/18/2019] [Indexed: 12/14/2022] Open
Abstract
Keratoconus (KC) is an ectatic corneal disease characterized by progressive thinning and irregular astigmatism, and a leading indication for corneal transplantation. KC-associated changes have been demonstrated for the entire cornea, but the pathological thinning and mechanical weakening is usually localized. We performed quantitative proteomics using Sequential Windowed Acquisition of All Theoretical Fragment Ion Mass Spectrometry (SWATH-MS) to analyze epithelial and stromal changes between the topographically-abnormal cone and topographically-normal non-cone regions of advanced KC corneas, compared to age-matched normal corneas. Expression of 20 epithelial and 14 stromal proteins was significantly altered (≥2 or ≤0.5-fold) between cone and non-cone in all 4 KC samples. Ingenuity pathway analysis illustrated developmental and metabolic disorders for the altered epithelial proteome with mitochondrion as the significant gene ontology (GO) term. The differential stromal proteome was related to cellular assembly, tissue organization and connective tissue disorders with endoplasmic reticulum protein folding as the significant GO term. Validation of selected protein expression was performed on archived KC, non-KC and normal corneal specimens by immunohistochemistry. This is the first time to show that KC-associated proteome changes were not limited to the topographically-thinner and mechanically-weakened cone but also non-cone region with normal topography, indicating a peripheral involvement in KC development.
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Tarnawska D, Jastrzebska M, Chrobak E, Kadela-Tomanek M, Weglarz B, Boryczka G, Dobrowolski D, Chełmecka E, Wrzalik R. Endogenous fluorescence can differentiate the keratoconic cornea. Exp Eye Res 2019; 181:178-184. [PMID: 30735658 DOI: 10.1016/j.exer.2019.02.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 01/03/2019] [Accepted: 02/03/2019] [Indexed: 11/15/2022]
Abstract
The purpose of the study was to investigate the endogenous fluorescence of the keratoconic cornea in order to analyze changes in the spectra due to the keratoconic stroma abnormalities. Twenty-two corneal buttons obtained from patients with keratoconus (KC, N = 22) at the time of penetrating keratoplasty were used. As a reference, twelve normal corneas (N = 12): ten from the Eye Bank and two from enucleated eyes due to choroidal melanoma were used. The fluorescence excitation/emission matrices (EEM) in the ranges of 250-400/260-600 nm were recorded. Healthy cornea, keratoconic cornea and sclera showed three main EEM bands, which correspond to the following fluorophores: tryptophan residues in the proteoglycan fraction of corneal/scleral stromas, naturally occurring collagen cross-links and the NAD(P)H fraction present in the metabolically active cells. Relative intensity factors S1, S2 and S3 describing the contribution of each kind of fluorophore to the total fluorescence of the tissue were calculated. Normal and keratoconic corneas show qualitatively similar fluorescence matrices, but the statistically significant differences in the mean values of the S1, S2 and S3 parameters for the KC and normal corneas were observed indicating changes in contribution of different fluorophores to the whole fluorescence of the tissue. Moreover, differences between multidimensional distribution of the relative intensity factors S1, S2 and S3 between these groups were demonstrated (p < 0.001). In conclusions: Differences in the relative intensity factors calculated on a basis of the fluorescence spectra can correspond to the changes found in the KC stroma regarding natural collagen cross-links and the proteoglycan fraction. These parameters well differentiate the KC and normal corneas that could serve as an additional tool for the keratoconus characterization.
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Affiliation(s)
- Dorota Tarnawska
- Department of Biophysics and Molecular Physics, A. Chelkowski Institute of Physics, Silesian Center for Education and Interdisciplinary Research, University of Silesia, 41-500 Chorzów, 75 Pułku Piechoty 1A, Poland; Department of Ophthalmology, District Railway Hospital, Panewnicka 65, 40-760 Katowice, Poland
| | - Maria Jastrzebska
- Department of Solid State Physics, A. Chelkowski Institute of Physics, Silesian Center for Education and Interdisciplinary Research, University of Silesia, 41-500 Chorzów, 75 Pułku Piechoty 1A, Poland.
| | - Elwira Chrobak
- Department of Organic Chemistry, School of Pharmacy with the Division of Laboratory Medicine in Sosnowiec, Medical University of Silesia in Katowice, 41-200 Sosnowiec, Jagiellońska 4, Poland
| | - Monika Kadela-Tomanek
- Department of Organic Chemistry, School of Pharmacy with the Division of Laboratory Medicine in Sosnowiec, Medical University of Silesia in Katowice, 41-200 Sosnowiec, Jagiellońska 4, Poland
| | - Beata Weglarz
- Department of Ophthalmology, District Railway Hospital, Panewnicka 65, 40-760 Katowice, Poland
| | - Grzegorz Boryczka
- Faculty of Medicine in Katowice, Medical University of Silesia, 40-752 Katowice, Medyków 18, Poland
| | - Dariusz Dobrowolski
- Department of Ophthalmology with Pediatric Unit & Tissue and Cells Bank, St. Barbara Hospital, Trauma Center, Plac Medyków 1, 41-200 Sosnowiec, Poland; Chair and Clinical Department of Ophthalmology, Faculty of Medicine and Division of Dentistry in Zabrze, Medical University of Silesia, 40-760 Katowice, Panewnicka 65, Poland
| | - Elżbieta Chełmecka
- Department of Statistics, School of Pharmacy with the Division of Laboratory Medicine, Medical University of Silesia, 41-200 Sosnowiec, Ostrogórska 30, Poland; Department of Instrumental Analysis, School of Pharmacy with the Division of Laboratory Medicine, Medical University of Silesia, 41-200 Sosnowiec, Ostrogórska 30, Poland
| | - Roman Wrzalik
- Department of Biophysics and Molecular Physics, A. Chelkowski Institute of Physics, Silesian Center for Education and Interdisciplinary Research, University of Silesia, 41-500 Chorzów, 75 Pułku Piechoty 1A, Poland
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Roy S, Yadav S, Dasgupta T, Chawla S, Tandon R, Ghosh S. Interplay between hereditary and environmental factors to establish an in vitro disease model of keratoconus. Drug Discov Today 2018; 24:403-416. [PMID: 30408528 DOI: 10.1016/j.drudis.2018.10.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 10/03/2018] [Accepted: 10/31/2018] [Indexed: 01/01/2023]
Abstract
Keratoconus (KC) is a bilateral corneal dystrophy and a multifactorial, multigenic disorder with an etiology involving a strong environmental component and complex inheritance patterns. The underlying pathophysiology of KC is poorly understood because of potential crosstalk between genetic-epigenetic variants possibly triggered by the environmental factors. Here, we decode the etiopathological basis of KC using genomic, transcriptomic, proteomic and metabolic approaches. The lack of relevant models that accurately imitate this condition has been particularly limiting in terms of the effective management of KC. Tissue-engineered in vitro models of KC could address this need and generate valuable insights into its etiopathology for the establishment of disease models to accelerate drug discovery.
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Affiliation(s)
- Subhadeep Roy
- Regenerative Engineering Laboratory, Department of Textile Technology, Indian Institute of Technology, New Delhi, India
| | - Saumya Yadav
- Cornea & Refractive Surgery Services, Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India
| | - Tanushree Dasgupta
- Regenerative Engineering Laboratory, Department of Textile Technology, Indian Institute of Technology, New Delhi, India
| | - Shikha Chawla
- Regenerative Engineering Laboratory, Department of Textile Technology, Indian Institute of Technology, New Delhi, India
| | - Radhika Tandon
- Cornea & Refractive Surgery Services, Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India
| | - Sourabh Ghosh
- Regenerative Engineering Laboratory, Department of Textile Technology, Indian Institute of Technology, New Delhi, India.
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Panahi Y, Azimi A, Naderi M, Jadidi K, Sahebkar A. An analytical enrichment-based review of structural genetic studies on keratoconus. J Cell Biochem 2018; 120:4748-4756. [PMID: 30260013 DOI: 10.1002/jcb.27764] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2018] [Accepted: 09/06/2018] [Indexed: 12/19/2022]
Abstract
Keratoconus is a progressive bilateral corneal protrusion that leads to irregular astigmatism and impairment of vision. Keratoconus is an etiologically heterogeneous corneal dystrophy and both environmental and genetic factors play a role in its etiopathogenesis. In this analytical review, we have studied all the genes that are structurally associated with keratoconus and have tried to explain the function of each gene and its association with other eye disorders in a concise way. In addition, using gene set enrichment analysis, it was attempted to find the most important impaired metabolic pathways in keratoconus. Several genetic studies have been carried out on keratoconus and several genes have been identified as risk factors involved in the etiology of the disease. In the current study, 16 studies, including nine association studies, five genome-wide association studies, one linkage study, and one meta-analysis, were reviewed and based on the 19 genes found, enrichment was performed and the most important metabolic pathways involved in the disease were identified. The enrichment results indicated that the two pathways, interleukin 1 processing and assembly of collagen fibrils, are significantly associated with the disease. Obviously, the results of this study, in addition to providing information about the genes involved in the disease, can provide an integrated insight into the gene-based etiology of keratoconus and therapeutic opportunities thereof.
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Affiliation(s)
- Yunes Panahi
- Chemical Injuries Research Center, System Biology and Poisonings Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran
| | - Ali Azimi
- Department of Ophthalmology, Poostchi Eye Research Center, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Mostafa Naderi
- Chemical Injuries Research Center, System Biology and Poisonings Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran
| | - Khosrow Jadidi
- Chemical Injuries Research Center, System Biology and Poisonings Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran
| | - Amirhossein Sahebkar
- Biotechnology Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences, Mashhad, Iran.,Neurogenic inflammation Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences, Mashhad, Iran.,School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Iran
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36
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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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Bao F, Zheng Y, Liu C, Zheng X, Zhao Y, Wang Y, Li L, Wang Q, Chen S, Elsheikh A. Changes in Corneal Biomechanical Properties With Different Corneal Cross-linking Irradiances. J Refract Surg 2018; 34:51-58. [PMID: 29315442 DOI: 10.3928/1081597x-20171025-01] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2017] [Accepted: 10/19/2017] [Indexed: 11/20/2022]
Abstract
PURPOSE To evaluate whether different corneal cross-linking (CXL) irradiances, all with the same delivered total energy, achieve similar increases in corneal material stiffness. METHODS One hundred twenty-six healthy white Japanese rabbits were randomly divided into seven groups (n = 18 each). After removing the epithelium of the left corneas, six groups were exposed to riboflavin (0.22% concentration by volume) and ultraviolet-A (370 nm) at different CXL irradiations, all with the same total dose (5.4 J/cm2), ranging from 3 mW/cm2 for 30 minutes to 90 mW/cm2 for 1 minute. The left corneas of the seventh group were exposed to riboflavin without irradiation. Twelve corneas of each group were prepared for inflation testing, where they were subjected to internal hydrostatic pressure simulating intraocular pressure, whereas the other six specimens were processed for electron microscopy measurements of fibril diameter and interfibrillar spacing. The inverse modeling process was used to estimate the tangent modulus of the tissue, which is considered an accurate measure of the material stiffness. RESULTS The stiffening effect of CXL decreased when using high irradiation/short duration settings. Compared with the group with no irradiation (NUVA group), the tangent modulus increases reduced from 212.5% in the 3mW/30min group to 196.8% in the 90mW/1min group. These increases were significant (P < .05) in the 3mW/30min and 9mW/10min groups, but became insignificant in other CXL groups. The interfibrillar spacing in the anterior 50 μm of the corneal stroma also reduced with high irradiation/short duration settings, changing from 20.05 ± 1.89 nm in the NUVA group down to 13.06 ± 2.07 and 14.37 ± 1.90 nm in the 3mW/30min and 9mW/10min groups, respectively. These changes were significant (P < .05) between non-adjacent groups, but became non-significant otherwise. The corresponding changes in fibril diameter were small and nonsignificant in all cases (P > .05). CONCLUSIONS Because the effect of CXL in stiffening the tissue and reducing the interfibrillar spacing consistently decreased with reducing the irradiance duration, the Bunsen-Roscoe law may not be readily applicable in the CXL of corneal tissue. [J Refract Surg. 2018;34(1):51-58.].
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Gutierrez-Bonet R, Ruiz-Medrano J, Peña-Garcia P, Catanese M, Sadeghi Y, Hashemi K, Gabison E, Ruiz-Moreno JM. Macular Choroidal Thickening in Keratoconus Patients: Swept-Source Optical Coherence Tomography Study. Transl Vis Sci Technol 2018; 7:15. [PMID: 29888113 PMCID: PMC5991807 DOI: 10.1167/tvst.7.3.15] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 04/30/2018] [Indexed: 02/03/2023] Open
Abstract
Purpose To determine the choroidal thickness (CT) profile in keratoconus (KC) patients using swept-source optical coherence tomography (SS-OCT). Methods This was a prospective, cross-sectional study. One hundred two eyes of 52 KC patients were studied using Pentacam and SS-OCT. The macular CT profile was created by manually measuring the distance between the retinal pigment epithelium and the choroid-sclera junction on horizontal b-scans at nine different macular locations. The results were compared to 93 eyes of 93 healthy controls. Results Mean age of the KC group was 34.9 ± 13.5 years and mean axial length (AL) was 24.1 ± 1.3 mm. Mean topographic KC classification (TKC) was 2.0; 39 eyes were classified as early KC (TKC <1–2), 34 eyes as moderate (TKC 2, 2–3), and 29 as advanced (TKC 3+). Mean subfoveal CT was 383.2 μm in KC patients and 280.5 μm in control group (P < 0.001). CT in KC patients was statistically thicker in all measure locations (P < 0.001). CT in KC eyes decreased with age, approaching control group at >45 years old, losing statistical significance (P = 0.37). Conclusions CT in KC patients is statistically thicker than in healthy population. After age 45, CT decreases approaching control group values. Translational Relevance This study describes changes in the CT profile of KC patients, a disease that was considered purely corneal. These choroidal changes argue that KC is a disease that likely involves several ocular structures other than the cornea, and could open new research lines related to the pathophysiology of KC.
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Affiliation(s)
| | - Jorge Ruiz-Medrano
- Jules Gonin Eye Hospital, Fondation Asile des Aveugles, Lausanne, Switzerland
| | | | | | - Yalda Sadeghi
- Jules Gonin Eye Hospital, Fondation Asile des Aveugles, Lausanne, Switzerland
| | - Katayoon Hashemi
- Jules Gonin Eye Hospital, Fondation Asile des Aveugles, Lausanne, Switzerland
| | | | - José M Ruiz-Moreno
- Castilla-La Mancha University, Albacete, Spain.,Puerta de Hierro-Majadahonda University Hospital, Madrid, Spain
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Hayes S, White T, Boote C, Kamma-Lorger CS, Bell J, Sorenson T, Terrill N, Shebanova O, Meek KM. The structural response of the cornea to changes in stromal hydration. J R Soc Interface 2018; 14:rsif.2017.0062. [PMID: 28592658 PMCID: PMC5493790 DOI: 10.1098/rsif.2017.0062] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Accepted: 05/12/2017] [Indexed: 11/12/2022] Open
Abstract
The primary aim of this study was to quantify the relationship between corneal structure and hydration in humans and pigs. X-ray scattering data were collected from human and porcine corneas equilibrated with polyethylene glycol (PEG) to varying levels of hydration, to obtain measurements of collagen fibril diameter, interfibrillar spacing (IFS) and intermolecular spacing. Both species showed a strong positive linear correlation between hydration and IFS2 and a nonlinear, bi-phasic relationship between hydration and fibril diameter, whereby fibril diameter increased up to approximately physiological hydration, H = 3.0, with little change thereafter. Above H = 3.0, porcine corneas exhibited a larger fibril diameter than human corneas (p < 0.001). Intermolecular spacing also varied with hydration in a bi-phasic manner but reached a maximum value at a lower hydration (H = 1.5) than fibril diameter. Human corneas displayed a higher intermolecular spacing than porcine corneas at all hydrations (p < 0.0001). Human and porcine corneas required a similar PEG concentration to reach physiological hydration, suggesting that the total fixed charge that gives rise to the swelling pressure is the same. The difference in their structural responses to hydration can be explained by variations in molecular cross-linking and intra/interfibrillar water partitioning.
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Affiliation(s)
- Sally Hayes
- Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, UK
| | - Tomas White
- Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, UK
| | - Craig Boote
- Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, UK
| | - Christina S Kamma-Lorger
- Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, UK.,ALBA Synchrotron Light Source, Cerdanyola del Vallès, Barcelona, Spain
| | - James Bell
- Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, UK
| | | | | | | | - Keith M Meek
- Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, UK
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Alkanaan A, Barsotti R, Kirat O, Almubrad T, Khan A, Akhtar S. Ultrastructural study of peripheral and central stroma of keratoconus cornea. Br J Ophthalmol 2017; 101:845-850. [PMID: 28416495 DOI: 10.1136/bjophthalmol-2016-309834] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2016] [Revised: 01/02/2017] [Accepted: 02/28/2017] [Indexed: 11/03/2022]
Abstract
PURPOSE Assess the lamellar organisation of the peripheral and central stroma of the keratoconus (KC) and normal cornea. METHODS Five normal and three KC corneas were fixed in 2.5% glutaraldehyde and processed for electron microscopy. The ultrathin sections were observed under JEOL 1400 TEM, and digital images were taken with a bottom-mounted 11-megapixel Quamisa camera, using the iTEM software. Measurements of the lamellae were carried out using the iTEM software. Statistical analysis was performed using the SPSS software. RESULTS The lamellar organisation at the centre and periphery of the KC cornea was disrupted by the presence of multiple undulations, which were more aggressive at the posterior stroma. Among the KC cornea, the mean lamellar thickness of the peripheral middle (1030.32±86.25 nm) and posterior (615.68±30.94 nm) stroma was also significantly (p<0.05) thinner than their corresponding areas of the central KC cornea (1151.1±48 nm; 783.57±31.10 nm). At the periphery of KC cornea, just above the Descemet's membrane (DM), small undulations appeared to emerge out from the DM. Furthermore, the anterior stroma of the peripheral cornea contained several lamellar sutures. The mean lamellar thickness of the peripheral and central KC cornea was significantly (p<0.0001) thinner than the corresponding areas of the normal cornea. CONCLUSION The present study reveals the involvement of lamellae in the peripheral stroma in the pathogenicity of the KC cornea. The emergence of small undulations in the DM suggests that the formation of undulation might be starting from the DM.
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Affiliation(s)
- Aljoharah Alkanaan
- Cornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia
| | - Robert Barsotti
- Department of Biomedical Science, Salus University, Philadelphia, Pennsylvania, USA
| | - Omar Kirat
- Department of Ophthalmology, King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia
| | - Turki Almubrad
- Cornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia
| | - Adnan Khan
- Cornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia
| | - Saeed Akhtar
- Cornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia
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Inflammatory Biomarkers Profile as Microenvironmental Expression in Keratoconus. DISEASE MARKERS 2016; 2016:1243819. [PMID: 27563164 PMCID: PMC4987484 DOI: 10.1155/2016/1243819] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 06/27/2016] [Indexed: 11/17/2022]
Abstract
Keratoconus is a degenerative disorder with progressive stromal thinning and transformation of the normal corneal architecture towards ectasia that results in decreased vision due to irregular astigmatism and irreversible tissue scarring. The pathogenesis of keratoconus still remains unclear. Hypotheses that this condition has an inflammatory etiopathogenetic component apart from the genetic and environmental factors are beginning to escalate in the research domain. This paper covers the most relevant and recent published papers regarding the biomarkers of inflammation, their signaling pathway, and the potentially new therapeutic options in keratoconus.
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Bao F, Geraghty B, Wang Q, Elsheikh A. Consideration of corneal biomechanics in the diagnosis and management of keratoconus: is it important? EYE AND VISION 2016; 3:18. [PMID: 27382596 PMCID: PMC4932704 DOI: 10.1186/s40662-016-0048-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Accepted: 06/13/2016] [Indexed: 11/10/2022]
Abstract
Keratoconus is a bilateral, non-inflammatory, degenerative corneal disease. The occurrence and development of keratoconus is associated with corneal thinning and conical protrusion, which causes irregular astigmatism. With the disruption of the collagen organization, the cornea loses its shape and function resulting in progressive visual degradation. Currently, corneal topography is the most important tool for the diagnosis of keratoconus, which may lead to false negatives among the patient population in the subclinical phase. However, it is now hypothesised that biomechanical destabilisation of the cornea may take place ahead of the topographic evidence of keratoconus, hence possibly assisting with disease diagnosis and management. This article provides a review of the definition, diagnosis, and management strategies for keratoconus based on corneal biomechanics.
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Affiliation(s)
- FangJun Bao
- The Affiliated Eye Hospital of Wenzhou Medical University, Wenzhou City, 325027 China ; The Institution of Ocular Biomechanics, Wenzhou Medical University, Wenzhou City, 325027 China
| | - Brendan Geraghty
- School of Engineering, University of Liverpool, Liverpool City, L69 3GH UK
| | - QinMei Wang
- The Affiliated Eye Hospital of Wenzhou Medical University, Wenzhou City, 325027 China ; The Institution of Ocular Biomechanics, Wenzhou Medical University, Wenzhou City, 325027 China
| | - Ahmed Elsheikh
- School of Engineering, University of Liverpool, Liverpool City, L69 3GH UK ; NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London City, UK
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Takaoka A, Babar N, Hogan J, Kim M, Price MO, Price FW, Trokel SL, Paik DC. An Evaluation of Lysyl Oxidase-Derived Cross-Linking in Keratoconus by Liquid Chromatography/Mass Spectrometry. Invest Ophthalmol Vis Sci 2016; 57:126-36. [PMID: 26780316 PMCID: PMC4727527 DOI: 10.1167/iovs.15-18105] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Purpose Current literature contains scant information regarding the extent of enzymatic collagen cross-linking in the keratoconus (KC) cornea. The aim of the present study was to examine levels of enzymatic lysyl oxidase–derived cross-links in stromal collagen in KC tissue, and to correlate the cross-link levels with collagen fibril stability as determined by thermal denaturation temperature (Tm). Methods Surgical KC samples (n = 17) and Eye-Bank control (n = 11) corneas of age 18 to 68 years were analyzed. The samples were defatted, reduced (NaBH4), hydrolyzed (6N HCl at 110°C for 18 hours), and cellulose enriched before analysis by C8 high-performance liquid chromatography equipped with parallel fluorescent and mass detectors in selective ion monitoring mode (20 mM heptafluorobutyric acid/methanol 70:30 isocratic at 1 mL/min). Nine different cross-links were measured, and the cross-link density was determined relative to collagen content (determined colorimetrically). The Tm was determined by differential scanning calorimetry. Results Cross-links detected were dihydroxylysinonorleucine (DHLNL), hydroxylysinonorleucine, lysinonorleucine (LNL), and histidinohydroxylysinonorleucine in both control and KC samples. Higher DHLNL levels were detected in KC, whereas the dominant cross-link, LNL, was decreased in KC samples. Decreased LNL levels were observed among KC ≤ 40 corneas. There was no difference in total cross-link density between KC samples and the controls. Pyridinolines, desmosines, and pentosidine were not detected. There was no notable correlation between cross-link levels with fibril instability as determined by Tm. Conclusions Lower levels of LNL in the KC cornea suggest that there might be a cross-linking defect either in fibrillar collagen or the microfibrillar elastic network composed of fibrillin.
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Affiliation(s)
- Anna Takaoka
- Department of Ophthalmology Columbia University College of Physicians and Surgeons, New York, New York, United States
| | - Natasha Babar
- Department of Ophthalmology Columbia University College of Physicians and Surgeons, New York, New York, United States
| | - Julia Hogan
- Department of Ophthalmology Columbia University College of Physicians and Surgeons, New York, New York, United States
| | - MiJung Kim
- Department of Ophthalmology Columbia University College of Physicians and Surgeons, New York, New York, United States
| | - Marianne O Price
- The Cornea Research Foundation of America, Indianapolis, Indiana, United States
| | | | - Stephen L Trokel
- Department of Ophthalmology Columbia University College of Physicians and Surgeons, New York, New York, United States
| | - David C Paik
- Department of Ophthalmology Columbia University College of Physicians and Surgeons, New York, New York, United States
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Abstract
PURPOSE To compare the corneal biomechanical properties and intraocular pressure (IOP) levels in patients with and without arcus senilis (AS). METHODS Ocular response analyzer measurements were performed on the right eyes of 37 patients with AS (group 1) and 37 control eyes (group 2). Corneal hysteresis, corneal resistance factor, Goldmann-correlated IOP, and corneal compensated IOP were recorded with Ocular response analyzer. Spherical equivalent value of the refractive errors, axial length, central corneal thickness, and IOP measured with Goldmann applanation tonometer were noted for each study eyes. Statistical analyses were performed with Student t, Kruskal-Wallis, and Pearson correlation tests. RESULTS Mean age was 67.6 ± 9.8 years in group 1 and 65.3 ± 8.1 years in group 2 (P = 0.308). Mean corneal hysteresis and corneal resistance factor readings were 9.8 ± 0.9 versus 10.6 ± 0.8 (P < 0.001) and 10.05 ± 1.07 versus 10.9 ± 0.9 (P < 0.001) in groups 1 and 2, respectively. Mean corneal compensated IOP and Goldmann-correlated IOP values were found as 16.1 ± 3.3 mm Hg versus 15.8 ± 2.6 mm Hg (P = 0.719) and 15.1 ± 3.3 mm Hg versus 15.0 ± 2.6 mm Hg (P = 0.912) in groups 1 and 2, respectively. There was no statistical difference in IOP measured with Goldmann applanation tonometer, central corneal thickness, spherical equivalent value of the refractive error, axial length measurements, and mean keratometry readings between the 2 groups (P = 0.983, P = 0.289, P = 0.938, P = 0.886, P = 0.07, respectively). CONCLUSIONS The mean corneal hysteresis and corneal resistance factor values of eyes with AS were lower when compared with the controls. This study demonstrated that AS may change the corneal biomechanical properties.
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Relationship of Structural Characteristics to Biomechanical Profile in Normal, Keratoconic, and Crosslinked Eyes. Cornea 2016; 34:791-6. [PMID: 25850703 DOI: 10.1097/ico.0000000000000434] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE To evaluate the correlation of corneal biomechanical parameters with structural characteristics in normal, keratoconic, and collagen crosslinked eyes. METHODS A prospective observational study that included 50 normal, 100 keratoconic, and 25 crosslinked eyes. All eyes were imaged using a Scheimpflug camera and an ocular response analyzer. The main outcome measures analyzed were central corneal thickness (CCT), corneal volume (CV), maximal keratometry (Kmax), corneal hysteresis (CH), and corneal resistance factor (CRF). RESULTS Significant differences were noted among all 3 groups of eyes for CCT, CV, Kmax, CH, and CRF values (P < 0.05 by analysis of variance). CH and CRF correlated negatively (CH, r = -0.40; CRF, r = -0.44; both P < 0.0001) with the Pentacam topographic keratoconus classification. Both CH and CRF correlated positively with CCT and CV for the normal, keratoconic, and crosslinked eyes. In contrast, significant negative correlations were observed between CH, CRF, and Kmax in the keratoconic eyes (CH, r = -0.43; CRF, r = -0.53; both P < 0.0001), whereas no association was noted for the normal and crosslinked eyes. CONCLUSIONS CH and CRF are influenced by the corneal structure, with higher values noted in corneas with greater thickness and volume. Corneal biomechanical parameters progressively decrease as the severity of keratoconus increases. After collagen crosslinking, the relationship of the corneal curvature to the biomechanical profile is similar to normal eyes.
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Theuring A, Spoerl E, Pillunat LE, Raiskup F. [Corneal collagen cross-linking with riboflavin and ultraviolet-A light in progressive keratoconus. Results after 10-year follow-up]. Ophthalmologe 2015; 112:140-7. [PMID: 25134461 DOI: 10.1007/s00347-014-3114-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
PURPOSE Riboflavin and ultraviolet-A induced cross-linking (CXL) is a promising therapeutic option to halt the progression of keratoconus. The aim of the study was to prove a long-term stabilizing effect of riboflavin and ultraviolet-A induced collagen CXL in young and otherwise healthy patients with progressive keratoconus and a corneal thickness of at least 400 μm on average 10 years after treatment. METHODS Corneal CXL was performed after removing epithelial tissue by instilling riboflavin 0.1% solution for 30 min before and during 30 min of ultraviolet-A irradiation (370 nm, 3 mW/cm(2)). This long-term retrospective study included 30 eyes of 20 patients with progressive keratoconus. Preoperative and postoperative examinations on average 10 years after treatment included best corrected visual acuity (BCVA), corneal topography (keratometry values KMAX, KMIN and KApex), corneal thickness (CT) and if available endothelial cell density. RESULTS The mean preoperative age was 28 ± 7 years (range 14-42 years), 4 patients were female (7 eyes) and 16 patients (23 eyes) were male. Preoperatively, the mean K-value on the apex of keratoconus was 62 ± 13.2 dpt which showed a statistically significant reduction after 10 years to 55 ± 8.1 dpt (p = 0.001). The mean KMAX (53 ± 8.2 versus 49 ± 6.6 dpt) and KMIN values (48 ± 5.5 vs. 45 ± 5.1 dpt) also showed a statistically significant decrease (p = 0.001). In comparison BCVA also showed a statistically significant preoperative and postoperative difference (p = 0.005). There was a significant improvement of BCVA by a mean of - 0.13 ± 0.25 logMAR. The mean change in corneal thickness at the 10-year follow up was 46 μm (p = 0.001). Bias possibly occurred because of a change of the measurement method from ultrasound pachymetry to optical pachymetry with Oculus Pentacam®. Neither corneal endothelium nor deeper structures suffered any damage. Only two patients had continuous progression of keratoconus and needed a reapplication of CXL. CONCLUSION The results of this study indicate that riboflavin and ultraviolet-A induced corneal CXL is a promising therapeutic option for progressing keratoconus to obtain long-term stabilization. There was a sustained improvement of all K-values and BCVA 10 years after treatment and CXL is minimally invasive and easy to handle. Side effects, such as endothelial damage did not occur.
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Affiliation(s)
- A Theuring
- Augenklinik, Universitätsklinik Dresden, Universitäts-Augenklinik Dresden, Fetscherstr. 74, 01307, Dresden, Deutschland,
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Chen X, Stojanovic A, Eidet JR, Utheim TP. Corneal collagen cross-linking (CXL) in thin corneas. EYE AND VISION 2015; 2:15. [PMID: 26605368 PMCID: PMC4657253 DOI: 10.1186/s40662-015-0025-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 05/10/2015] [Accepted: 08/19/2015] [Indexed: 11/14/2022]
Abstract
Corneal collagen cross-linking (CXL) is a therapeutic procedure aiming at increasing the corneal stiffness in the keratoconus eyes by induction of cross-links within the extracellular matrix. It is achieved by ultraviolet-A (370 nm) irradiation of the cornea after saturation with the photosensitizer riboflavin. In the conventional CXL protocol, a minimum de-epithelialized corneal thickness of 400 μm is recommended to avoid potential irradiation damage to the corneal endothelium. In advanced keratoconus, however, stromal thickness is often lower than 400 μm, which limits the application of CXL in that category. Efforts have been undertaken to modify the conventional CXL procedure to be applicable in thin corneas. The current review discusses different techniques employed to achieve this end and their results. The overall safety and efficacy of the modified CXL protocols are good, as most of them managed to halt the progression of keratectasia without postoperative complications. However, the evidence of safety and efficacy in the use of modified CXL protocols is still limited to few studies with few patients involved. Controlled studies with long-term follow-up are required to confirm the safety and efficacy of the modified protocols.
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Affiliation(s)
- Xiangjun Chen
- SynsLaser Kirurgi, Oslo and Tromsø, Norway ; Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Aleksandar Stojanovic
- SynsLaser Kirurgi, Oslo and Tromsø, Norway ; Faculty of Medicine, University of Oslo, Oslo, Norway ; Eye Department, University Hospital North Norway, Tromsø, Norway
| | - Jon Roger Eidet
- Department of Medical Biochemistry, Oslo University Hospital, Oslo, Norway
| | - Tor Paaske Utheim
- Department of Medical Biochemistry, Oslo University Hospital, Oslo, Norway ; Department of Oral Biology, Faculty of Dentistry, University of Oslo, Oslo, Norway
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Liu R, Zhao J, Xu Y, Li M, Niu L, Liu H, Sun L, Chu R, Zhou X. Femtosecond Laser-Assisted Corneal Small Incision Allogenic Intrastromal Lenticule Implantation in Monkeys: A Pilot Study. Invest Ophthalmol Vis Sci 2015; 56:3715-20. [PMID: 26047173 DOI: 10.1167/iovs.14-15296] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Lenticule implantation can be used to correct vision problems. However, it is significantly restrained by the sources of autologous lenticules. The aim of the present study was to investigate the feasibility and effects of femtosecond laser-assisted corneal small incision allogenic intrastromal lenticule implantation (AILI) in monkeys. METHODS Six healthy adult monkeys were included in this study. Femtosecond lenticule extraction (-4.0 diopter [D] correction, 5.0-mm optical zone) was performed in one eye of two monkeys and both eyes of one monkey. Each extracted refractive lenticule was allogenically transplanted into a femtosecond laser-created corneal stromal pocket in one eye of the other two monkeys and one monkey's both eyes. Pre- and postoperative (1 or 3 days, 1 month, and 6 months) slit lamp microscopy, corneal topography, anterior segment optical coherence tomography, and in vivo confocal microscopy were performed. RESULTS Corneal edema occurred in the early postoperative days with a large number of hyperreflective particles around the borders. Corneal tissue edema gradually decreased. Nerve fiber regeneration could be detected in the lenticule layer at 6 months. Overall, 3.27 ± 1.2 D corneal power was increased at 6 months, accounting for 82% of the intended correction. At the same time point, corneal stroma was 69 ± 11 μm thicker than preoperative ones and was roughly equal to the maximum thickness of implanted lenticules. No significant complications were observed. CONCLUSIONS The AILI technique seems to be feasible and safe for increasing corneal stromal thickness and changing corneal refractive power, which may provide a useful method for treatment of keratoectasia, presbyopia, and hyperopia.
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Affiliation(s)
- Rui Liu
- Key Laboratory of Myopia Ministry of Health, Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, China
| | - Jing Zhao
- Key Laboratory of Myopia Ministry of Health, Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, China
| | - Ye Xu
- Key Laboratory of Myopia Ministry of Health, Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, China
| | - Meiyan Li
- Key Laboratory of Myopia Ministry of Health, Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, China
| | - Lingling Niu
- Key Laboratory of Myopia Ministry of Health, Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, China
| | | | - Ling Sun
- Key Laboratory of Myopia Ministry of Health, Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, China
| | - Renyuan Chu
- Key Laboratory of Myopia Ministry of Health, Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, China
| | - Xingtao Zhou
- Key Laboratory of Myopia Ministry of Health, Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, China
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Wang X, Huang Y, Jastaneiah S, Majumdar S, Kang JU, Yiu SC, Stark W, Elisseeff JH. Protective Effects of Soluble Collagen during Ultraviolet-A Crosslinking on Enzyme-Mediated Corneal Ectatic Models. PLoS One 2015; 10:e0136999. [PMID: 26325407 PMCID: PMC4556688 DOI: 10.1371/journal.pone.0136999] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 08/11/2015] [Indexed: 11/19/2022] Open
Abstract
Collagen crosslinking is a relatively new treatment for structural disorders of corneal ectasia, such as keratoconus. However, there is a lack of animal models of keratoconus, which has been an obstacle for carefully analyzing the mechanisms of crosslinking and evaluating new therapies. In this study, we treated rabbit eyes with collagenase and chondroitinase enzymes to generate ex vivo corneal ectatic models that simulate the structural disorder of keratoconus. The models were then used to evaluate the protective effect of soluble collagen in the UVA crosslinking system. After enzyme treatment, the eyes were exposed to riboflavin/UVA crosslinking with and without soluble type I collagen. Corneal morphology, collagen ultrastructure, and thermal stability were evaluated before and after crosslinking. Enzyme treatments resulted in corneal curvature changes, collagen ultrastructural damage, decreased swelling resistance and thermal stability, which are similar to what is observed in keratoconus eyes. UVA crosslinking restored swelling resistance and thermal stability, but ultrastructural damage were found in the crosslinked ectatic corneas. Adding soluble collagen during crosslinking provided ultrastructural protection and further enhanced the swelling resistance. Therefore, UVA crosslinking on the ectatic model mimicked typical clinical treatment for keratoconus, suggesting that this model replicates aspects of human keratoconus and could be used for investigating experimental therapies and treatments prior to translation.
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Affiliation(s)
- Xiaokun Wang
- Wilmer Eye Institute, School of Medicine, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Yong Huang
- Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Sabah Jastaneiah
- Ophthalmology, King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia
| | - Shoumyo Majumdar
- Department of Material Science and Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Jin U. Kang
- Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Samuel C. Yiu
- Wilmer Eye Institute, School of Medicine, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Walter Stark
- Wilmer Eye Institute, School of Medicine, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Jennifer H. Elisseeff
- Wilmer Eye Institute, School of Medicine, Johns Hopkins University, Baltimore, Maryland, United States of America
- Department of Material Science and Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
- * E-mail:
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