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Bradford S, Luo S, Brown D, Juhasz T, Jester J. A review of the epithelial and stromal effects of corneal collagen crosslinking. Ocul Surf 2023; 30:150-159. [PMID: 37683969 PMCID: PMC10993773 DOI: 10.1016/j.jtos.2023.09.003] [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: 04/21/2023] [Revised: 08/31/2023] [Accepted: 09/05/2023] [Indexed: 09/10/2023]
Abstract
Induced corneal collagen crosslinking and mechanical stiffening via ultraviolet-A photoactivation of riboflavin (UVA CXL) is now a common treatment for corneal ectasia and Keratoconus. Some effects of the procedure such as induced mechanical stiffening, corneal flattening, and cellular toxicity are well-known, but others remain more controversial. Authors report a variety of contradictory effects, and provide evidence based on individual results and observations. A full understanding of the effects of and mechanisms behind this procedure are essential to predicting its outcome. A growing interest in modifications to the standard UVA CXL protocol, such as transepithelial or accelerated UVA CXL, makes analyzing the literature as a whole more urgent. This review presents an analysis of both the agreed-upon and contradictory results reported and the various methods used to obtain them.
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Affiliation(s)
- Samantha Bradford
- Department of Ophthalmology and Biomedical Engineering, University of California, Irvine, Irvine, CA, USA.
| | - Shangbang Luo
- Department of Ophthalmology and Biomedical Engineering, University of California, Irvine, Irvine, CA, USA
| | - Donald Brown
- Department of Ophthalmology and Biomedical Engineering, University of California, Irvine, Irvine, CA, USA
| | - Tibor Juhasz
- Department of Ophthalmology and Biomedical Engineering, University of California, Irvine, Irvine, CA, USA
| | - James Jester
- Department of Ophthalmology and Biomedical Engineering, University of California, Irvine, Irvine, CA, USA
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2
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Al-Mahrouqi H, Cheung IMY, Angelo L, Yu TY, Gokul A, Ziaei M. Therapeutic non-ectasia applications of cornea cross-linking. Clin Exp Optom 2023; 106:580-590. [PMID: 36690333 DOI: 10.1080/08164622.2022.2159790] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 08/28/2022] [Accepted: 10/10/2022] [Indexed: 01/25/2023] Open
Abstract
Corneal cross-linking is a photopolymerization technique traditionally used to strengthen corneal tissue. Corneal cross-linking utilizes riboflavin (vitamin B2) as a photosensitizer and ultraviolet-A light (UVA) to create strong covalent bonds within the corneal stroma, increasing tissue stiffness. Multiple studies have demonstrated corneal cross-linking's effectiveness in treating corneal ectasia, a progressive, degenerative, and non-inflammatory thinning disorder, as quantified by key tomographic, refractive, and visual parameters. Since its introduction two decades ago, corneal cross-linking has surpassed its original application in halting corneal ectatic disease and its application has expanded into several other areas. Corneal cross-linking also possesses antibacterial, antienzymolytic and antioedematous properties, and has since become a tool in treating microbial keratitis, correcting refractive error, preventing iatrogenic ectasia, stabilising bullous keratopathy and controlling post keratoplasty ametropia. This review provides an overview of the current evidence base for the therapeutic non-ectasia applications of cornea cross-linking and looks at future developments in the field.
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Affiliation(s)
| | | | - Lize Angelo
- Department of Ophthalmology, University of Auckland, Auckland, New Zealand
| | - Tzu-Ying Yu
- Department of Ophthalmology, Greenlane Clinical Centre, Auckland District Health Board, Auckland, New Zealand
| | - Akilesh Gokul
- Department of Ophthalmology, University of Auckland, Auckland, New Zealand
| | - Mohammed Ziaei
- Department of Ophthalmology, University of Auckland, Auckland, New Zealand
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3
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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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4
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Yang K, Xu L, Wang S, Zhu M, Fan Q, Gu Y, Wang Y, Wang Q, Zhao D, Pang C, Ren S. A Bibliometric Analysis of 100 Most-Cited Articles on Corneal Cross-Linking. Front Med (Lausanne) 2022; 9:904077. [PMID: 35721090 PMCID: PMC9199002 DOI: 10.3389/fmed.2022.904077] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Accepted: 05/02/2022] [Indexed: 11/13/2022] Open
Abstract
Background Highly cited papers are expected to have high-quality data that significantly contribute to the body of knowledge. The study aimed to evaluate the characters of the 100 most-cited articles on corneal cross-linking (CXL) through a bibliometric analysis. Materials and Methods The Web of Science database was searched to identify papers published from 1950 to 2020. A bibliometric analysis of the top 100-cited articles was conducted in the current study. The citation differences between basic research, clinical research, and reviews were compared by Kruskal-Wallis test. The association between citations and publication year was evaluated by Spearman correlation analysis. The VOSviewer software was used to create networks of co-authorship and keywords map. Results The median values of the number of citations, citations/year since publication, and citations since 2013 were 101, 9.5, and 11.92, respectively. A total of 61% of articles were clinical research. The citations since 2013 of clinical research were lower than basic research and the reviews (all p < 0.001). The publication year was positively correlated with the number of publications (r = 0.665, p = 0.013), and the total number of citations decreased for basic research (r = -0.447, p = 0.017), and clinical research (r = -0.433, p < 0.001). The J REFRACT SURG publishes the highest number of articles. The corresponding authors were predominantly from the Italy (N = 17), Germany (N = 16), and United States (N = 15). Spoerl Eberhard has the highest number of citations and total link strength with 15 articles. Extensive collaboration existed among the main core nodes containing "cross-linking (N = 45)," "riboflavin (N = 44)," and "ultraviolet A (UVA) (N = 42)." Conclusion The present study focused on the comprehensive analysis of the top 100-cited articles on the CXL research, providing insight into research developments over the past decades.
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Affiliation(s)
- Kaili Yang
- Henan Provincial People's Hospital, Henan Eye Hospital, Henan Eye Institute, People's Hospital of Zhengzhou University, Zhengzhou, China
| | - Liyan Xu
- Henan Provincial People's Hospital, Henan Eye Hospital, Henan Eye Institute, People's Hospital of Zhengzhou University, Zhengzhou, China
| | - Shaopei Wang
- Henan Provincial People's Hospital, Henan Eye Hospital, Henan Eye Institute, People's Hospital of Zhengzhou University, Zhengzhou, China
| | - Meng Zhu
- Henan Provincial People's Hospital, Henan Eye Hospital, Henan Eye Institute, People's Hospital of Zhengzhou University, Zhengzhou, China
| | - Qi Fan
- Henan Provincial People's Hospital, Henan Eye Hospital, Henan Eye Institute, People's Hospital of Zhengzhou University, Zhengzhou, China
| | - Yuwei Gu
- Henan Provincial People's Hospital, Henan Eye Hospital, Henan Eye Institute, People's Hospital of Zhengzhou University, Zhengzhou, China
| | - Yawen Wang
- Henan Provincial People's Hospital, Henan Eye Hospital, Henan Eye Institute, People's Hospital of Zhengzhou University, Zhengzhou, China
| | - Qing Wang
- Henan Provincial People's Hospital, Henan Eye Hospital, Henan Eye Institute, People's Hospital of Zhengzhou University, Zhengzhou, China
| | - Dongqing Zhao
- Henan Provincial People's Hospital, Henan Eye Hospital, Henan Eye Institute, People's Hospital of Zhengzhou University, Zhengzhou, China
| | - Chenjiu Pang
- Henan Provincial People's Hospital, Henan Eye Hospital, Henan Eye Institute, People's Hospital of Zhengzhou University, Zhengzhou, China
| | - Shengwei Ren
- Henan Provincial People's Hospital, Henan Eye Hospital, Henan Eye Institute, People's Hospital of Zhengzhou University, Zhengzhou, China
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Wang M, Corpuz CCC, Zhang F. Shaping Eyeballs by Scleral Collagen Cross-Linking: A Hypothesis for Myopia Treatment. Front Med (Lausanne) 2021; 8:655822. [PMID: 34277654 PMCID: PMC8282923 DOI: 10.3389/fmed.2021.655822] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 06/08/2021] [Indexed: 11/13/2022] Open
Abstract
The global prevalence of myopia has brought to the attention of the different eye and vision specialists, who make way to control its progression. Evidence have shown that a proactive reshaping of the eyeball is the core point of myopia developing process, which particularly includes the weakening, thinning, and expanding of the sclera. Thus, the sclera is considered to be a prime target for therapeutic manipulation in halting progressive myopia. In the past decades, corneal collagen cross-linking has been applied in clinical practice for treating aberrant corneal remodeling diseases. In this article, we hypothesize that scleral collagen cross-linking (SXL) has a huge potential in stabilizing myopic process by shaping the eyeball and preventing the aberrant scleral remodeling. In contrast with the current methods of optometry correction, such as physiotherapy, pharmacotherapy, spectacles, contact lenses, refractive surgeries, etc., eyeball-shaping method using SXL is a fundamental intervention which aims at the pathogenesis of progressive visual loss of myopia. Compared with the current posterior scleral reinforcement, the most advantage of SXL is that there is no allotransplant into the myopic eye, which means less expenditure, lower risk, and easier to handle in operating.
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Affiliation(s)
- Mengmeng Wang
- Hebei Ophthalmology Key Lab, Hebei Eye Hospital, Xingtai, China
| | | | - Fengju Zhang
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China
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6
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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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7
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Abrishamchi R, Abdshahzadeh H, Hillen M, Hafezi N, Torres-Netto EA, Aslanides IM, Chen S, Randleman JB, Hafezi F. High-Fluence Accelerated Epithelium-Off Corneal Cross-Linking Protocol Provides Dresden Protocol-Like Corneal Strengthening. Transl Vis Sci Technol 2021; 10:10. [PMID: 34542574 PMCID: PMC8458988 DOI: 10.1167/tvst.10.5.10] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To assess whether optimized technical settings for accelerated epithelium-off corneal cross-linking may lead to increases in biomechanical stiffness similar to the benchmark 30-minute epithelium-off Dresden protocol. Methods Three-hundred porcine eyes were divided equally into six groups for analysis. All samples underwent epithelial debridement and soaking with 0.1% iso-osmolar riboflavin solution for 20 minutes. Corneal cross-linking (CXL) was performed using epithelium-off protocols varying in acceleration and total fluence (intensity in mW/cm² * time in minutes, total fluence in J/cm²): standard (S)-CXL (3*30, 5.4), accelerated (A)-CXL (9*10, 5.4), A-CXL (9*13'20″, 7.2), A-CXL (18*6'40″, 7.2), and A-CXL (18*9'15″, 10). Control corneas were not irradiated. The elastic modulus of 5-mm wide corneal strips was measured as an indicator of corneal stiffness. Results All irradiated groups had significantly higher elastic modulus than controls (P < 0.05), with a stiffening effect of 133% S-CXL (3*30, 5.4), 122% A-CXL (9*10, 5.4), 120% A-CXL (9*13'20″, 7.2), 114% A-CXL (18*6'40″, 7.2) and 149% A-CXL (18*9'15″, 10). The high-fluence accelerated epithelium-off protocol (18*9'15″, 10) showed the highest stiffening effect. Elastic modulus at 5% strain (1%-5% strain) showed significant differences between A-CXL (18*9'15″, 7.2) and three other accelerated protocols: A-CXL (9*10, 5.4; P = 0.01), A-CXL (9*13'20″, 7.2; P = 0.003), and A-CXL (18*6'40″, 10; P = 0.0001). Conclusions An accelerated high-fluence epithelium-off CXL protocol (18 mW/cm² for 9'15″) was identified to provide a significantly greater stiffening effect than any other accelerated protocols and is indistinguishable from the Dresden protocol, with accelerating irradiation times ranging from 30 to 9 minutes; by combining gentle acceleration with higher fluence, such a protocol does not require supplemental oxygen. Translational Relevance This A-CXL (18*9'15″, 10) protocol has the potential to become a new standard in epithelium-off CXL, delivering Dresden protocol-like strengthening over a shorter period.
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Affiliation(s)
- Reyhaneh Abrishamchi
- Laboratory for Ocular Cell Biology, Center for Applied Biotechnology and Molecular Medicine, University of Zurich, Zurich, Switzerland.,Faculty of Medicine, University of Geneva, Geneva, Switzerland.,ELZA Institute, Dietikon/Zurich, Switzerland
| | - Hormoz Abdshahzadeh
- Laboratory for Ocular Cell Biology, Center for Applied Biotechnology and Molecular Medicine, University of Zurich, Zurich, Switzerland.,Faculty of Medicine, University of Geneva, Geneva, Switzerland.,ELZA Institute, Dietikon/Zurich, Switzerland
| | - Mark Hillen
- ELZA Institute, Dietikon/Zurich, Switzerland
| | | | - Emilio A Torres-Netto
- Laboratory for Ocular Cell Biology, Center for Applied Biotechnology and Molecular Medicine, University of Zurich, Zurich, Switzerland.,Faculty of Medicine, University of Geneva, Geneva, Switzerland.,Department of Ophthalmology, Paulista School of Medicine, Federal University of São Paulo, São Paulo, Brazil.,Department of Ophthalmology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Ioannis M Aslanides
- Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China.,Emmetropia Mediterranean Eye Institute, Heraklion, Crete, Greece
| | - Shihao Chen
- Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - J Bradley Randleman
- Department of Ophthalmology, The Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Farhad Hafezi
- Laboratory for Ocular Cell Biology, Center for Applied Biotechnology and Molecular Medicine, University of Zurich, Zurich, Switzerland.,Faculty of Medicine, University of Geneva, Geneva, Switzerland.,ELZA Institute, Dietikon/Zurich, Switzerland.,Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China.,USC Roski Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
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8
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Chan E, Snibson GR. Current status of corneal collagen cross‐linking for keratoconus: a review. Clin Exp Optom 2021; 96:155-64. [DOI: 10.1111/cxo.12020] [Citation(s) in RCA: 71] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Revised: 09/24/2012] [Accepted: 10/03/2012] [Indexed: 11/29/2022] Open
Affiliation(s)
- Elsie Chan
- Royal Victorian Eye and Ear Hospital, Melbourne, Australia,
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9
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Yang J, Ding C, Tang L, Deng F, Yang Q, Wu H, Chen L, Ni Y, Huang L, Zhang M. Novel Modification of Collagen: Realizing Desired Water Solubility and Thermostability in a Conflict-Free Way. ACS OMEGA 2020; 5:5772-5780. [PMID: 32226856 PMCID: PMC7097890 DOI: 10.1021/acsomega.9b03846] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Accepted: 01/23/2020] [Indexed: 05/22/2023]
Abstract
Because of poor water solubility and low thermostability, the application of collagen is limited seriously in fields such as injectable biomaterials and cosmetics. In order to overcome the two drawbacks simultaneously, a novel bifunctional modifier based on the esterification of polyacrylic acid (PAA) with N-hydroxysuccinimide (NHS) was prepared. The esterification degree of PAA-NHS esters was increased upon increasing the NHS dose, which was confirmed by Fourier-transform infrared (FTIR) and nuclear magnetic resonance spectrascopy. FTIR results indicated that the triple helix of the modified collagens remained integrated, whereas the molecular weight became larger, as reflected by the sodium dodecyl sulfate-polyacrylamide gel electrophoresis pattern. The modified collagens displayed excellent water solubility under neutral condition, owing to lower isoelectric point (3.1-4.3) than that of native collagen (7.1). Meanwhile, denaturation temperatures of the modified collagens were increased by 4.8-5.9 °C after modification. The modified collagen displayed hierarchical microstructures, as reflected by field-emission scanning electron microscopy, while atomic force microscopy further revealed a "fishing net-like" network in the nanoscale, reflecting a unique aggregation behavior of collagen macromolecules after modification. As a whole, the PAA-NHS ester as a bifunctional modifier endowed collagen with desired water solubility and thermostability in a conflict-free manner, which was beneficial to the process and application of the water-soluble collagen.
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Affiliation(s)
- Junhui Yang
- College
of Materials Engineering, Fujian Agriculture
and Forestry University, Fuzhou 350002, PR China
| | - Cuicui Ding
- College
of Ecological Environment and Urban Construction, Fujian University of Technology, Fuzhou 350108, PR China
| | - Lele Tang
- College
of Materials Engineering, Fujian Agriculture
and Forestry University, Fuzhou 350002, PR China
| | - Feng Deng
- College
of Materials Engineering, Fujian Agriculture
and Forestry University, Fuzhou 350002, PR China
| | - Qili Yang
- College
of Materials Engineering, Fujian Agriculture
and Forestry University, Fuzhou 350002, PR China
| | - Hui Wu
- College
of Materials Engineering, Fujian Agriculture
and Forestry University, Fuzhou 350002, PR China
| | - Lihui Chen
- College
of Materials Engineering, Fujian Agriculture
and Forestry University, Fuzhou 350002, PR China
| | - Yonghao Ni
- College
of Materials Engineering, Fujian Agriculture
and Forestry University, Fuzhou 350002, PR China
- Department
of Chemical Engineering and Limerick Pulp & Paper Centre, University of New Brunswick, Fredericton E3B 5A3, Canada
| | - Liulian Huang
- College
of Materials Engineering, Fujian Agriculture
and Forestry University, Fuzhou 350002, PR China
| | - Min Zhang
- College
of Materials Engineering, Fujian Agriculture
and Forestry University, Fuzhou 350002, PR China
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10
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Liao C, Lin X, Keel S, Ha J, Yang X, He M. Effects of corneal crosslinking on corneal shape stabilization after orthokeratology. Sci Rep 2020; 10:2357. [PMID: 32047218 PMCID: PMC7012905 DOI: 10.1038/s41598-020-59157-2] [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] [Received: 05/29/2019] [Accepted: 01/06/2020] [Indexed: 12/04/2022] Open
Abstract
Orthokeratology (Ortho-K) works to reshape cornea and is the only non-surgical way to enable vision without corrective aids. However, its effect is only temporary, and successful stabilization requires ongoing Ortho-K wear to maintain the reshaping effect. Corneal crosslinking (CXL) is a commonly-used technique in clinical practice to stabilize corneal shape in keratoconic eyes. However, whether or not CXL can stabilize corneal shape after Ortho-K in normal cornea has not been reported. Therefore, this proof-of-concept study using 2 rhesus monkeys aimed to determine the efficacy of the combined procedure. One monkey wore Ortho-K bilaterally for 24 hours, and the other from 6 pm to 8 am for 7 days. The left eyes of both monkeys underwent CXL after Ortho-K while the contralateral eye served as control. Results showed a gradual regression of corneal shape in all eyes with or without CXL. However, eyes underwent CXL regressed more slowly than the control eyes. The control eyes and the CXL treatment eye in the 7-day Ortho-K monkey regressed completely at last, while the CXL treatment eye in the 24 h Ortho-K monkey maintained a corneal flattening of −1.48 D 27 days after procedure. These findings suggest CXL can slow the regression of Ortho-K for a short duration, but cannot sustain its effect according to the current protocol.
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Affiliation(s)
- Chimei Liao
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Xingyan Lin
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Stuart Keel
- Center for Eye Research Australia; Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, Australia
| | - Jason Ha
- Faculty of Medicine, Nursing and Health Sciences, Monash University, Clayton, Australia
| | - Xiao Yang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
| | - Mingguang He
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
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11
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Daood U, Sauro S, Pichika MR, Omar H, Liang Lin S, Fawzy AS. Novel riboflavin/VE-TPGS modified universal dentine adhesive with superior dentine bond strength and self-crosslinking potential. Dent Mater 2019; 36:145-156. [PMID: 31818524 DOI: 10.1016/j.dental.2019.11.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Revised: 09/07/2019] [Accepted: 11/11/2019] [Indexed: 12/12/2022]
Abstract
OBJECTIVE To modify a universal dentine adhesive with different concentrations of riboflavin and D-Alpha 1000 Succinate polyethylene (VE-TPGS) as a chemical enhancer and to assess the micro-tensile bond strength (24h/12 months), determine resin penetration, measurement of intermolecular interactions and cytotoxicity. MATERIALS AND METHODS An experimental adhesive system based on bis-GMA, HEMA and hydrophobic monomer was doped with RF0.125 (RF - Riboflavin) or RF/VE-TPGS (0.25/0.50) and submitted to μTBS evaluation. Resin dentine slabs were prepared and examined using SEM and TEM. Adhesion force was analysed on ends of AFM cantilevers deflection. Quenched peptide assays were performed using fluorescence scanner and wavelengths set to 320nm and 405nm. Cytotoxicity was assessed using human peripheral blood mononuclear cell line. Molecular docking studies were carried out using Schrödinger small-molecule drug discovery suite 2018-2. Data from viable cell results was analyzed using one-way ANOVA. Bond strength values were analysed by two-way ANOVA. Nonparametric results were analyzed using a Kruskal-Wallis test at a 0.05 significance level. RESULTS RF/VE-TPGS0.25 groups showed highest bond strength results after 24-h storage in artificial saliva (p<0.05). RF/VE-TPGS0.50 groups showed increased bond strength after 12-months of ageing. RF/VE-TPGS modified adhesives showed appreciable presence of a hybrid layer. Packing fraction indicated solid angle profiles describing well sized density and topology relations for the RF/VE-TPGS adhesives, in particular with the RF/VE-TPGS0.50 specimens. Qualitative analysis of the phenotype of macrophages was prominently CD163+ in the RF/VE-TPGS0.50. Both the compounds showed favourable negative binding energies as expressed in terms of 'XP GScore'. CONCLUSION New formulations based on the incorporation of RF/VE-TPGS in universal adhesives may be of significant potential in facilitating penetration, distribution and uptake of riboflavin within the dentine surface.
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Affiliation(s)
- U Daood
- Clinical Dentistry Division, Restorative Division, School of Dentistry, International Medical University Kuala Lumpur, 126, Jalan Jalil Perkasa 19, Bukit Jalil 57000, Wilayah Persekutuan Kuala Lumpur, Malaysia
| | - Salvatore Sauro
- Dental Biomaterials and Minimally Invasive Dentistry, Departmento de Odontologia, Facultad de Ciencias de la Salud Universidad, CEU-Cardenal Herrera, Spain
| | - Malikarjuna Rao Pichika
- Department of Pharmaceutical Chemistry, School of Pharmacy, International Medical University Kuala Lumpur, 126, Jalan Jalil Perkasa 19, Bukit Jalil 57000, Wilayah Persekutuan Kuala Lumpur, Malaysia
| | - Hanan Omar
- Missouri School of Dentistry and Oral Health (MOSDOH) - ATSU, United States
| | - Seow Liang Lin
- Clinical Dentistry Division, Restorative Division, School of Dentistry, International Medical University Kuala Lumpur, 126, Jalan Jalil Perkasa 19, Bukit Jalil 57000, Wilayah Persekutuan Kuala Lumpur, Malaysia
| | - A S Fawzy
- UWA Dental School, University of Western Australia, 17 Monash Avenue, Nedlands, WA 6009, Australia.
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Subasinghe SK, Ogbuehi KC, Dias GJ. Current perspectives on corneal collagen crosslinking (CXL). Graefes Arch Clin Exp Ophthalmol 2018; 256:1363-1384. [PMID: 29623463 DOI: 10.1007/s00417-018-3966-0] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2017] [Revised: 02/20/2018] [Accepted: 03/23/2018] [Indexed: 12/13/2022] Open
Abstract
Corneal collagen crosslinking has revolutionized the treatment of keratoconus and post-refractive corneal ectasia in the past decade. Corneal crosslinking with riboflavin and ultraviolet A is proposed to halt the progression of keratectasia. In the original "Conventional Dresden Protocol" (C-CXL), the epithelium is removed prior to the crosslinking process to facilitate better absorption of riboflavin into the corneal stroma. Studies analyzing its short- and long-term outcomes revealed that although there are inconsistencies as to the effectiveness of this technique, the advantages prevail over the disadvantages. Therefore, corneal crosslinking (CXL) is widely used in current practice to treat keratoconus. In an attempt to improve the visual and topographical outcomes of C-CXL and to minimize time-related discomfort and endothelial-related side effects, various modifications such as accelerated crosslinking and transepithelial crosslinking methods have been introduced. The comparison of outcomes of these modified techniques with C-CXL has also returned contradictory results. Hence, it is difficult to clearly identify an optimal procedure that can overcome issues associated with the CXL. This review provides an up-to-date analysis on clinical and laboratory findings of these popular crosslinking protocols used in the treatment of keratoconus. It is evident from this review that in general, these modified techniques have succeeded in minimizing the immediate complications of the C-CXL technique. However, there were contradictory viewpoints regarding their effectiveness when compared with the conventional technique. Therefore, these modified techniques need to be further investigated to arrive at an optimal treatment option for keratoconus.
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Affiliation(s)
- Sandeepani K Subasinghe
- Department of Anatomy, University of Otago, P.O. Box 913, 270 Great King Street, Dunedin, 9054, New Zealand.
| | - Kelechi C Ogbuehi
- Ophthalmology Section, Department of Medicine, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
| | - George J Dias
- Department of Anatomy, University of Otago, P.O. Box 913, 270 Great King Street, Dunedin, 9054, New Zealand
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Zyablitskaya M, Munteanu EL, Nagasaki T, Paik DC. Second Harmonic Generation Signals in Rabbit Sclera As a Tool for Evaluation of Therapeutic Tissue Cross-linking (TXL) for Myopia. J Vis Exp 2018. [PMID: 29364259 DOI: 10.3791/56385] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Methods to strengthen tissue by introducing chemical bonds (non-enzymatic cross-linking) into structural proteins (fibrillar collagens) for therapy include photochemical cross-linking and tissue cross-linking (TXL) methods. Such methods for inducing mechanical tissue property changes are being employed to the cornea in corneal thinning (mechanically weakened) disorders such as keratoconus as well as the sclera in progressive myopia, where thinning and weakening of the posterior sclera occurs and likely contributes to axial elongation. The primary target proteins for such tissue strengthening are fibrillar collagens which constitute the great majority of dry weight proteins in the cornea and sclera. Fortuitously, fibrillar collagens are the main source of second harmonic generation signals in the tissue extracellular space. Therefore, modifications of the collagen proteins, such as those induced through cross-linking therapies, could potentially be detected and quantitated through the use of second harmonic generation microscopy (SHGM). Monitoring SHGM signals through the use of a laser scanning microscopy system coupled with an infrared excitation light source is an exciting modern imaging method that is enjoying widespread usage in the biomedical sciences. Thus, the present study was undertaken in order to evaluate the use of SHGM microscopy as a means to measure induced cross-linking effects in ex vivo rabbit sclera, following an injection of a chemical cross-linking agent into the sub-Tenon's space (sT), an injection approach that is standard practice for causing ocular anesthesia during ophthalmologic clinical procedures. The chemical cross-linking agent, sodium hydroxymethylglycinate (SMG), is from a class of cosmetic preservatives known as formaldehyde releasing agents (FARs). Scleral changes following reaction with SMG resulted in increases in SHG signals and correlated with shifts in thermal denaturation temperature, a standard method for evaluating induced tissue cross-linking effects.
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Affiliation(s)
- Mariya Zyablitskaya
- Department of Ophthalmology, Columbia University College of Physicians and Surgeons
| | - E Laura Munteanu
- Confocal and Specialized Microscopy Shared Resource, Herbert Irving Comprehensive Cancer Center, Columbia University
| | - Takayuki Nagasaki
- Department of Ophthalmology, Columbia University College of Physicians and Surgeons
| | - David C Paik
- Department of Ophthalmology, Columbia University College of Physicians and Surgeons;
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Zyablitskaya M, Takaoka A, Munteanu EL, Nagasaki T, Trokel SL, Paik DC. Evaluation of Therapeutic Tissue Crosslinking (TXL) for Myopia Using Second Harmonic Generation Signal Microscopy in Rabbit Sclera. Invest Ophthalmol Vis Sci 2017; 58:21-29. [PMID: 28055099 PMCID: PMC5225996 DOI: 10.1167/iovs.16-20241] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Purpose Second harmonic generation signals (SHG) are emitted preferentially from collagenous tissue structures and have been used to evaluate photochemically-induced (CXL) crosslinking changes in the cornea. Since therapeutic tissue crosslinking (TXL) using sodium hydroxymethylglycinate (SMG) of the sclera is a potential treatment for high myopia, we explored the use of SHG microscopy to evaluate the effects. Methods Single sub-Tenon's (sT) injections (400 μL) using SMG (40-400 mM) were made at the equatorial 12 o'clock position of the right eye of cadaveric rabbit heads (n = 16 pairs). After 3.5 hours, confocal microscopy (CM) was performed using 860 nm two-photon excitation and 400 to 450 nm emission. Pixel density and fiber bundle "waviness" analyses were performed on the images. Crosslinking effects were confirmed using thermal denaturation (Tm) temperature. Comparison experiments with riboflavin photochemical crosslinking were done. Results Therapeutic tissue crosslinking localization studies indicated that crosslinking changes occurred at the site of injection and in adjacent sectors. Second harmonic generation signals revealed large fibrous collagenous bundled structures that displayed various degrees of waviness. Histogram analysis showed a nearly 6-fold signal increase in 400 mM SMG over 40 mM. This corresponded to a ΔTm = 13°C for 400 mM versus ΔTm = 4°C for 40 mM. Waviness analysis indicated increased fiber straightening as a result of SMG CXL. Conclusions Second harmonic generation signal intensity and fiber bundle waviness is altered by scleral tissue crosslinking using SMG. These changes provide insights into the macromolecular changes that are induced by therapeutic crosslinking technology and may provide a method to evaluate connective tissue protein changes induced by scleral crosslinking therapies.
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Affiliation(s)
- Mariya Zyablitskaya
- Department of Ophthalmology, Columbia University College of Physicians and Surgeons, New York, New York, United States
| | - Anna Takaoka
- Department of Ophthalmology, Columbia University College of Physicians and Surgeons, New York, New York, United States
| | - Emilia L Munteanu
- Confocal and Specialized Microscopy Shared Resource, Herbert Irving Comprehensive Cancer Center, Columbia University, New York, New York, United States
| | - Takayuki Nagasaki
- Department of Ophthalmology, Columbia University College of Physicians and Surgeons, New York, New York, 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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Biomechanical and Histopathologic Effects of Pulsed-Light Accelerated Epithelium-On/-Off Corneal Collagen Cross-Linking. Cornea 2017; 36:854-859. [DOI: 10.1097/ico.0000000000001219] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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16
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Corneal collagen crosslinking for corneal ectasias: a review. Eur J Ophthalmol 2016; 27:253-269. [PMID: 28009397 DOI: 10.5301/ejo.5000916] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/15/2016] [Indexed: 11/20/2022]
Abstract
PURPOSE To review the published literature on corneal collagen crosslinking (CXL). METHODS Importance has been placed on seminal publications, systemic reviews, meta-analyses, and randomized controlled clinical trials. Where such evidence was not available, cohort studies, case-controlled studies, and case series with follow-up greater than 12 months were examined. RESULTS Corneal collagen crosslinking with riboflavin and ultraviolet A (UVA) 370 nm radiation appears to be capable of arresting the progression of ectatic corneal disorders, with most studies reporting significant improvements in visual, keratometric, and topographic measurements. Its mode of action at the molecular level is undetermined. Follow-up is limited to 5-10 years but suggests sustained stability and enhancement in corneal shape with time. Nearly all published long-term data and comparative studies are with epithelium-off techniques. Epithelium-on investigations suggest some efficacy but less than with epithelium-off treatments and long-term data are unavailable. Accelerated techniques with higher UVA fluencies and shorter treatments times, delivering the same UVA energy dosage, are the subject of recent investigation, with some laboratory and clinical studies suggesting reduced efficacy compared to the standard 3 mW/cm2 for 30 minutes irradiation procedure. Combined methodologies of CXL with techniques such as photorefractive keratectomy and intrastromal rings show promise but long-term follow-up is indicated. Sight-threatening complications of CXL are rare. CONCLUSIONS Studies of epithelium-off CXL with irradiation at 3 mW/cm2 for 30 minutes support its efficacy. Refinement in techniques may allow for safer and more rapid procedures with less patient discomfort but require further investigation.
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17
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Pupil response to tropicamide following corneal crosslinking. Eur J Ophthalmol 2016; 26:394-7. [PMID: 26833233 DOI: 10.5301/ejo.5000758] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/11/2016] [Indexed: 11/20/2022]
Abstract
PURPOSE To evaluate the effect of corneal crosslinking (CXL) with ultraviolet A (UVA) irradiation on pupil response to tropicamide 0.5% instillation. METHODS This prospective interventional study enrolled 17 patients (19 eyes) with progressive keratoconus who underwent CXL with UVA irradiation. Central corneal thickness (CCT) was evaluated with the use of anterior segment optical coherence tomography (Visante OCT 3.0). Pupil diameter was measured with the use of Colvard infrared pupillometer before the instillation of tropicamide 0.5% and after the instillation of tropicamide every 5 minutes for total duration of 30 minutes. Corneal epithelial integrity was examined with the use of fluorescein dye staining. Measurements were performed 1 day preoperatively and 1 month postoperatively, with emphasis on simulating the same light conditions regarding the pupil measurements. RESULTS No intraoperative or postoperative complications were observed in any of the patients. Mean CCT decreased significantly (p<0.001) 1 month postoperatively. Mean postoperative pupil size did not change significantly at any time point compared to the mean preoperative measurements. CONCLUSIONS The CXL procedure seems not to impair effectiveness of topical drugs, using pupil size measurements after tropicamide 0.5% instillation.
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Xu K, Chan TCY, Vajpayee RB, Jhanji V. Corneal Collagen Cross-linking: A Review of Clinical Applications. Asia Pac J Ophthalmol (Phila) 2015; 4:300-6. [PMID: 26381468 DOI: 10.1097/apo.0000000000000145] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Corneal collagen cross-linking (CXL) has been shown to slow down or stop the progression of keratoconus. In addition, CXL has been applied in cases of corneal ectasia. Recent reports of the use of CXL in cases of infectious keratitis have generated further interest in this treatment modality. This review discusses the principle, clinical uses, and complications associated with CXL.
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Affiliation(s)
- Kunyong Xu
- From the *Department of Ophthalmology, Queen's University, Kingston, Canada; †Department of Ophthalmology, Hotel Dieu and Kingston General Hospitals, Kingston, Canada; ‡Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong; §Hong Kong Eye Hospital, Hong Kong; ¶Centre for Eye Research Australia, University of Melbourne, Melbourne, Australia; ∥Vision Eye Institute, Royal Victorian Eye and Ear Hospital, North West Academic Centre University of Melbourne, Melbourne, Australia; and **Department of Ophthalmology, Prince of Wales Hospital, Hong Kong
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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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20
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Padmanabhan P, Radhakrishnan A, Venkataraman AP, Gupta N, Srinivasan B. Corneal changes following collagen cross linking and simultaneous topography guided photoablation with collagen cross linking for keratoconus. Indian J Ophthalmol 2015; 62:229-35. [PMID: 23619500 PMCID: PMC4005242 DOI: 10.4103/0301-4738.111209] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
PURPOSE To compare the outcome of Collagen cross-linking (CXL) with that following topography-guided customized ablation treatment (T-CAT) with simultaneous CXL in eyes with progressive keratoconus. MATERIALS AND METHODS This was a prospective, non-randomized single centre study of 66 eyes with progressive keratoconus. Of these, 40 eyes underwent CXL and 26 eyes underwent T-CAT + CXL. The refractive, topographic, tomographic and aberrometric changes measured at baseline, 1, 3 and 6 months post-operatively were compared between both groups. RESULTS After a mean follow-up of 7.7 ± 1.3 months, the mean retinoscopic cylinder decreased by 1.02 ± 3.16 D in the CXL group ( P = 0.1) and 2.87 ± 3.22 D in the T-CAT + CXL group ( P = 0.04). The Best corrected visual acuity increased by 2 lines or more in 10% of eyes in the CXL group and in 23.3% of eyes in the T-CAT + CXL group. The mean steepest-K reduced by 0.40 ± 3.71 D ( P = 0.77) in the CXL group and by 2.91 ± 2.01D ( P = 0.03) in the T-CAT + CXL group. The sag factor and surface asymmetry index showed no significant change in the CXL group but reduced by 3.59 ± 5.94 D ( P = 0.01) and 0.72 ± 1.18 ( P = 0.02) respectively in the T-CAT + CXL group. There was a significant increase in the highest posterior corneal elevation in both groups (9.57 ± 14.93 μ in the CXL group and 7.85 ± 9.25 μ in the T-CAT + CXL group, P ≤ 0.001 for both). There was significantly greater reduction of mean coma ( P < 0.001) and mean higher-order aberrations ( P = 0.01) following T-CAT + CXL compared to CXL. CONCLUSIONS CAT + CXL is an effective approach to confer biomechanical stability and to improve the corneal contour in eyes with keratoconus and results in better refractive, topographic and aberrometric outcomes than CXL alone.
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Affiliation(s)
- Prema Padmanabhan
- Department of Cornea and Refractive Surgery, Medical Research Foundation, Sankara Nethralaya, Chennai, Tamil Nadu, India
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One-year clinical study on efficacy of corneal cross-linking in Indian children with progressive keratoconus. Cornea 2015; 33:919-22. [PMID: 25055145 DOI: 10.1097/ico.0000000000000197] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE The aim of this study was to assess the efficacy of corneal collagen cross-linking (CXL) with riboflavin using ultraviolet-A light in children with progressive keratoconus. METHODS Thirty-five eyes of 24 children with progressive keratoconus aged between 9 and 16 years were included in this retrospective study. Ocular examination included the best-corrected visual acuity (BCVA), dilated refraction, slit-lamp exam, and corneal topography (Orbscan II) at 6 and 12 months. All children were treated with riboflavin with ultraviolet-A light under topical anesthesia and all completed 1-year follow-up. RESULTS The mean age of the children was 13.65 years (range, 9-16 years). Follow-up was for a period of 1 year. The mean of preoperative keratometry (Kmax) was 55.11 ± 5.34 diopters (D), whereas the mean of postoperative Kmax was reduced to 53.87 ± 4.99 D. The mean preoperative pachymetry was 412.31 ± 36.54 μm, which changed to 361.31 ± 58.04 μm postoperatively. At 1 year, improvement in the BCVA was noted in 18 (51.42%) eyes, stabilization in 12 (34.28%), and worsening in 5 (14.28%) eyes. Overall, the BCVA improved by 1 line, which was statistically significant (P = 0.0368) at the end of 1 year. There was a reduction in both cylindrical and spherical equivalent, of which, the latter was not statistically significant (P = 0.77), whereas the former was of weak statistical significance (P = 0.061). No complications were reported. CONCLUSIONS CXL with riboflavin is an effective procedure for children with progressive keratoconus. The results show stabilization, improvement, or both in keratoconus in terms of BCVA and corneal curvature after CXL in most children.
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Bourges JL, Robert AM, Robert L. A genetic anomaly of oriented collagen biosynthesis and cross-linking: Keratoconus. ACTA ACUST UNITED AC 2014; 63:24-31. [PMID: 25468492 DOI: 10.1016/j.patbio.2014.10.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Accepted: 10/20/2014] [Indexed: 11/20/2022]
Abstract
Oriented collagen biosynthesis is one of the major mechanisms involved in tissue and organ formation during development. Corneal biogenesis is one example. Defects in this process lead to anomalies in tissue structure and function. The transparency of cornea and its achievement are a good example as well as its pathological modifications. Keratoconus is one example of this type of pathologies, involving also inappropriate cross-linking of collagen fibers. Among the tentatives to correct this anomaly, the riboflavin-potentiated UV-cross-linking (CXL) of keratoconus corneas appears clinically satisfactory, although none of the experiments and clinical results published prove effective cross-linking. The published results are reviewed in this article.
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Affiliation(s)
- J L Bourges
- Centre d'ophtalmologie HUPC, hôpital Hôtel-Dieu, Assistance publique-Hôpitaux de Paris, 1, place du Parvis-Notre-Dame, 75181 Paris cedex 04, France; Faculté de médicine Paris Descartes, université Sorbonne Paris Cité, 15, rue de l'École-de-Médecine, 75006 Paris, France
| | - A M Robert
- Faculté de médicine Paris Descartes, université Sorbonne Paris Cité, 15, rue de l'École-de-Médecine, 75006 Paris, France; Laboratoire de recherche ophtalmologique, hôpital Hôtel-Dieu, Assistance publique-Hôpitaux de Paris, 1, place du Parvis-Notre-Dame, 75181 Paris cedex 04, France
| | - L Robert
- Faculté de médicine Paris Descartes, université Sorbonne Paris Cité, 15, rue de l'École-de-Médecine, 75006 Paris, France; Laboratoire de recherche ophtalmologique, hôpital Hôtel-Dieu, Assistance publique-Hôpitaux de Paris, 1, place du Parvis-Notre-Dame, 75181 Paris cedex 04, France.
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Urs R, Lloyd HO, Silverman RH. Acoustic radiation force for noninvasive evaluation of corneal biomechanical changes induced by cross-linking therapy. JOURNAL OF ULTRASOUND IN MEDICINE : OFFICIAL JOURNAL OF THE AMERICAN INSTITUTE OF ULTRASOUND IN MEDICINE 2014; 33:1417-26. [PMID: 25063407 PMCID: PMC4457329 DOI: 10.7863/ultra.33.8.1417] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
OBJECTIVES To noninvasively measure changes in corneal biomechanical properties induced by ultraviolet-activated riboflavin cross-linking therapy using acoustic radiation force (ARF). METHODS Cross-linking was performed on the right eyes of 6 rabbits, with the left eyes serving as controls. Acoustic radiation force was used to assess corneal stiffness before treatment and weekly for 4 weeks after treatment. Acoustic power levels were within US Food and Drug Administration guidelines for ophthalmic safety. Strain, determined from ARF-induced displacement of the front and back surfaces of the cornea, was fit to the Kelvin-Voigt model to determine the elastic modulus (E) and coefficient of viscosity (η). The stiffness factor, the ratio of E after treatment to E before treatment, was calculated for treated and control eyes. At the end of 4 weeks, ex vivo thermal shrinkage temperature analysis was performed for comparison with in vivo stiffness measurements. One-way analysis of variance and Student t tests were performed to test for differences in E, η, the stiffness factor, and corneal thickness. RESULTS Biomechanical stiffening was immediately evident in cross-linking-treated corneas. At 4 weeks after treatment, treated corneas were 1.3 times stiffer and showed significant changes in E (P= .006) and η (P= .007), with no significant effect in controls. Corneal thickness increased immediately after treatment but did not differ significantly from the pretreatment value at 4 weeks. CONCLUSIONS Our findings demonstrate a statistically significant increase in stiffness in cross-linking-treated rabbit corneas based on in vivo axial stress/strain measurements obtained using ARF. The capacity to noninvasively monitor corneal stiffness offers the potential for clinical monitoring of cross-linking therapy.
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Affiliation(s)
- Raksha Urs
- Department of Ophthalmology, Columbia University Medical Center, New York, New York USA (R.U., H.O.L., R.H.S.); and Frederic L. Lizzi Center for Biomedical Engineering, Riverside Research Institute, New York, New York USA (R.H.S.).
| | - Harriet O Lloyd
- Department of Ophthalmology, Columbia University Medical Center, New York, New York USA (R.U., H.O.L., R.H.S.); and Frederic L. Lizzi Center for Biomedical Engineering, Riverside Research Institute, New York, New York USA (R.H.S.)
| | - Ronald H Silverman
- Department of Ophthalmology, Columbia University Medical Center, New York, New York USA (R.U., H.O.L., R.H.S.); and Frederic L. Lizzi Center for Biomedical Engineering, Riverside Research Institute, New York, New York USA (R.H.S.)
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O'Brart DPS. Corneal collagen cross-linking: a review. JOURNAL OF OPTOMETRY 2014; 7:113-24. [PMID: 25000866 PMCID: PMC4087180 DOI: 10.1016/j.optom.2013.12.001] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Accepted: 11/14/2013] [Indexed: 05/04/2023]
Abstract
The aim was to review the published literature on corneal collagen cross-linking. The emphasis was on the seminal publications, systemic reviews, meta-analyses and randomized controlled trials. Where such an evidence did not exist, selective large series cohort studies, case controlled studies and case series with follow-up preferably greater than 12 months were included. Riboflavin/Ultraviolet A (UVA) corneal collagen cross-linking appears to be the first treatment modality to halt the progression of keratoconus and other corneal ectatic disorders with improvement in visual, keratometric and topographic parameters documented by most investigators. Its precise mechanism of action at a molecular level is as yet not fully determined. Follow-up is limited to 4-6 years at present but suggests continued stability and improvement in corneal shape with time. Most published data are with epithelium-off techniques. Epithelium-on studies suggest some efficacy but less than with the epithelium-off procedures and long-term data are not currently available. The use of Riboflavin/UVA CXL for the management of infectious and non-infectious keratitis appears very promising. Its use in the management of bullous keratopathy is equivocal. Investigation of other methodologies for CXL are under investigation.
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Affiliation(s)
- David P S O'Brart
- Keratoconus Research Institute, Department of Ophthalmology, St. Thomas' Hospital, London SE1 7EH, United Kingdom.
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Corneal collagen cross-linking with and without epithelial removal: a contralateral study with 0.5% hypotonic riboflavin solution. BIOMED RESEARCH INTERNATIONAL 2014; 2014:619398. [PMID: 25050368 PMCID: PMC4090564 DOI: 10.1155/2014/619398] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Accepted: 05/27/2014] [Indexed: 11/18/2022]
Abstract
PURPOSE Our main purpose was to compare safety and efficacy in the treatment of progressive keratoconus with "epithelium-on" and "epithelium-off" corneal collagen cross-linking (CXL). Our secondary purpose was to evaluate efficacy of CXL when hypotonic 0.5% riboflavin is used as photosensitizer. METHODS One eye of 20 patients with bilateral progressive keratoconus was randomly treated for "epithelium-on" CXL (group 1) while the fellow eye underwent "epithelium-off" CXL (group 2). Hypotonic 0.5% riboflavin was used in both groups. Visual acuity, refraction, corneal topography, and wavefront aberrometry were evaluated at baseline and after 1, 6, and 12 months. Specular microscopy was performed on 10 patients preoperatively and after 12 months. Postoperative pain was evaluated using a patient questionnaire. RESULTS Uncorrected and corrected distance visual acuity improved significantly in both groups. Refraction, topography, and aberrometry showed nonsignificant changes from the preoperative status throughout the 12-month follow-up in both groups. Moreover, the outcomes between the groups were comparable at all follow-up points. Endothelial cell-count was stable. Postoperative pain length was shorter in group 1 (P < 0.001). CONCLUSION "Epithelium-on" and "epithelium-off" CXL using hypotonic 0.5% riboflavin were equally safe and effective in stabilization of keratoconus. Topography and aberrometry outcomes in both groups failed to show any significant improvements. This study is registered at ClinicalTrials.gov: NCT01181219.
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Abstract
PURPOSE The aim was to investigate the changes in collagen type 1 and type 3 in rabbit corneas undergoing corneal crosslinking with ultraviolet A and riboflavin and to analyze the possible mechanisms of corneal haze formation. METHODS After removal of the central epithelium, the right corneas of 60 New Zealand rabbits were crosslinked with riboflavin and ultraviolet A, and 10 additional rabbits were used as the control group. The animals were killed 3, 7, 15, 30, 90, and 180 days postoperatively. Collagen type 1 and type 3 were analyzed using picrosirius red stain by means of polarized light microscopy. The biochemical changes in collagen type 3 at the time points indicated above were determined by Western blot analyses. RESULTS Collagen type 3 was significantly increased 30 days after corneal crosslinking compared with that in the control cornea, gradually increased until reaching its maximum value 90 days after riboflavin and ultraviolet A crosslinking, and then decreased until it returned to the normal state 180 days after crosslinking. There were no significant changes in collagen type 1 over time after corneal crosslinking. In agreement with the picrosirius red staining results, the western blot analyses showed that collagen type 3 was detected 15 days after the crosslinking treatment and continued to be present. However, 180 days after the crosslinking treatment, collagen type 3 could not be found in the crosslinked corneas. CONCLUSIONS These findings suggest that ultraviolet A/riboflavin crosslinking results in collagen type 3 synthesis and degradation, which may offer at least a partial explanation for the formation of corneal haze.
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Goldich Y, Barkana Y, Wussuku Lior O, Marcovich AL, Hirsh A, Avni I, Zadok D. Corneal collagen cross-linking for the treatment of progressive keratoconus: 3-year prospective outcome. Can J Ophthalmol 2014; 49:54-9. [DOI: 10.1016/j.jcjo.2013.09.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Accepted: 09/13/2013] [Indexed: 10/25/2022]
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Iovieno A, Moramarco A, Coassin M, Baiocchi S, Caporossi A, Fontana L. Big bubble DALK after CXL in keratoconic patients. J Refract Surg 2014; 29:801. [PMID: 24307631 DOI: 10.3928/1081597x-20131115-02] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Tan HY, Chang YL, Lo W, Hsueh CM, Chen WL, Ghazaryan AA, Hu PS, Young TH, Chen SJ, Dong CY. Characterizing the morphologic changes in collagen crosslinked-treated corneas by Fourier transform-second harmonic generation imaging. J Cataract Refract Surg 2013; 39:779-88. [PMID: 23608570 DOI: 10.1016/j.jcrs.2012.11.036] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Revised: 10/17/2012] [Accepted: 11/09/2012] [Indexed: 10/26/2022]
Abstract
PURPOSE To evaluate the efficacy of using forward second harmonic generation (SHG) and 2-dimensional fast Fourier-transform (2D-FFT) analysis for the label-free characterization and quantification of morphologic changes in the corneal stroma after collagen crosslinking (CXL). SETTING Department of Physics, National Taiwan University, Taipei, Taiwan. DESIGN Experimental study. METHODS En face forward SHG imaging and 2D-FFT analysis were performed on ex vivo porcine corneas at the depths of 100, 200, 400, and 800 μm. Morphologic changes in stromal collagen fiber in control, ultraviolet-A (UVA), riboflavin, and riboflavin-UVA treated porcine corneas were assessed. Hematoxylin-eosin staining and Sirius red staining were performed for comparison. RESULTS Corneas after CXL treatment tended to have collagen fibers that were wavy compared with the linear pattern in normal corneas. Quantitative 2D-FFT analysis of forward SHG images also showed an increase in the standard deviations of the distribution of stromal collagen fiber orientations, which is indicative of the changed pattern of crosslinked stromal collagen fibers. CONCLUSIONS Second harmonic generation imaging showed the morphologic changes in stromal collagen after CXL treatment. The linear collagen fibers in normal corneal stroma became wavy after treatment. With the introduction of 2D-FFT analysis, the morphologic changes can be quantified.
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Affiliation(s)
- Hsin-Yuan Tan
- Institute of Biomedical Engineering, College of Medicine and Engineering, National Taiwan University, Taipei, Taiwan
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Klebe S, Callahan T, Power JHT. Peroxiredoxin I and II in human eyes: cellular distribution and association with pterygium and DNA damage. J Histochem Cytochem 2013; 62:85-96. [PMID: 24152995 DOI: 10.1369/0022155413508409] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Peroxiredoxin I and II are both 2-Cys members of the peroxiredoxin family of antioxidant enzymes and inactivate hydrogen peroxide. On western blotting, both enzymes appeared as 22-kD proteins and were present in the sclera, retina and iris. Immunohistochemistry showed strong cytoplasmic labeling in the basal cells of the corneal epithelial layer and the corneoscleral limbus. The melanocytes within the stroma of the iris and the anterior epithelial cells of the lens also showed strong cytoplasmic labeling. The fibrous structure of the stroma and the posterior surface of the ciliary body were also labeled. There was also strong labeling for both enzymes in the photoreceptors and the inner and outer plexiform layers of the retina. There was increased labeling of peroxiredoxin I and II in pterygium. In normal conjunctiva and cornea, only the basal cell layer showed labeling for peroxiredoxin I and II, whereas, in pterygia, there was strong cytoplasmic labeling in most cells involving the full thickness of the epithelium. Co-localization of the DNA oxidation product 8-hydroxy-2'-deoxyguanosine antibody with the nuclear dye 4',6'-diamidino-2-phenylindole dihydrochloride indicated that the majority of the oxidative damage was cytoplasmic; this suggested that the mitochondrial DNA was most affected by the UV radiation in this condition.
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Affiliation(s)
- Sonja Klebe
- Departments of Anatomical Pathology and Human Physiology, School of Medicine, Flinders University, South Australia (SK, TC, JHP)
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Choi S, Shin JH, Cheong Y, Jin KH, Park HK. Structural and biomechanical effects of photooxidative collagen cross-linking with photosensitizer riboflavin and 370 nm UVA light on human corneoscleral tissues. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2013; 19:1334-1340. [PMID: 23739323 DOI: 10.1017/s1431927613001669] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
This study quantitatively investigated the immediate effects of a photooxidative collagen cross-linking treatment with photosensitizer riboflavin (RF) and 370 nm UVA light in in vitro human corneoscleral collagen fibrils using histology, thickness, scanning electron microscopy, and atomic force microscopy analyses. Twenty 8 x 2 mm corneoscleral strips were dissected sagittally from donor tissue using a scalpel. Four parameters were investigated, including the density, thickness, adhesion force, and stiffness of corneoscleral tissues before and after the collagen cross-linking treatment. The RFUVA-catalyzed collagen cross-linking treatment led to an increase in the density of both corneal (8%) and scleral (23%) stromal collagens. However, there was no difference in corneoscleral thickness. Furthermore, RFUVA-catalyzed collagen cross-linking treatment led to an increased biomechanical response of corneosclera: 25 and 8% increases in corneoscleral stiffness, and 24 and 22% increases in corneoscleral adhesion force. The collagen cross-linking treatment through RF-sensitized photoreaction may cause structural and biomechanical changes in the collagen fibril network of the cornea and the sclera. This is due to narrowing of the interfibrillar spacing and the stromal edema.
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Affiliation(s)
- Samjin Choi
- Department of Biomedical Engineering & Healthcare Industry Research Institute, Kyung Hee University, Seoul 130-701, Korea
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Jeyalatha V, Jambulingam M, Gupta N, Padmanabhan P, Madhavan HN. Study on polymethylmethacrylate ring in protecting limbal stem cells during collagen cross-linking. Ophthalmic Res 2013; 50:113-6. [PMID: 23867297 DOI: 10.1159/000351644] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Accepted: 04/04/2013] [Indexed: 11/19/2022]
Abstract
OBJECTIVE The UV rays used in the collagen cross-linking (CXL) procedure seem to cause potential damage to the limbal stem cells. This study was designed to evaluate the ability of polymethylmethacrylate (PMMA) hemiannulus as an alternative to protect corneal limbal stem cells during CXL. METHODS Ten freshly enucleated human cadaveric eyeballs were subjected to the corneal CXL procedure. The cadaveric eye ball was divided into 2 sectors: A and B. Sector A was left unprotected, while sector B was covered by a PMMA shield. Limbal biopsies from both sectors before and after the procedure were analyzed. Each limbal tissue was placed on human amniotic membrane (HAM) to check the cultivability and was subjected to marker studies using reverse transcriptase PCR. RESULTS Before CXL, biopsies from both sectors showed growth on HAM. After CXL, biopsies from sector A showed no growth on HAM while 2 out of the 10 from sector B covered with the PMMA ring did show growth on HAM. The putative stem-cell marker ABCG2 was negative in all the samples from sector A after CXL and was positive in 2 out of the 10 samples from sector B. CONCLUSION Covering the limbal region with PMMA offers partial protection of the limbus from the UV rays during the CXL procedure.
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Affiliation(s)
- Vimalin Jeyalatha
- L&T Microbiology Research Centre, Vision Research Foundation, Chennai, India
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Abstract
PURPOSE To determine the interlamellar cohesive strength (ICS) of porcine cornea before and after collagen cross-linking using riboflavin and ultraviolet A (UVA) irradiation. METHODS Corneal flaps, 130 μm thick, were created with a microkeratome. Cross-linking was accomplished with 0.1% riboflavin and UVA irradiation for 30 minutes (3 mW/cm, 5.4 J/cm) at a distance of 10 mm. Two experiments were performed. (1) The maximal ICS between corneal flap and the stroma was determined and histological examination was performed. (2) The mean stromal ICS was measured. Untreated eyes served as controls in all experiments. RESULTS The mean maximum flap-stroma ICS was 0.088 ± 0.046 N/mm in the experimental group and 0.012 ± 0.004 N/mm in the control group (P = 0.009). In experiment 2, incomplete (2 mm long) corneal flaps were used and the mean stromal ICS was 0.750 ± 0.077 N/mm in the experimental group and 0.338 ± 0.046 N/mm in the control group (P < 0.0001). Histological examination showed an irregular ragged separation of the surface in the stromal margin of the cornea with cross-linking, but a smooth separation surface in the cornea without cross-linking. CONCLUSIONS Collagen cross-linking activated by riboflavin/UVA increases ICS in porcine corneas.
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Wittig-Silva C, Chan E, Pollock G, Snibson GR. Localized Changes in Stromal Reflectivity After Corneal Collagen Cross-Linking Observed With Different Imaging Techniques. J Refract Surg 2013; 29:410-6. [DOI: 10.3928/1081597x-20130410-02] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Accepted: 03/05/2013] [Indexed: 11/20/2022]
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Chiang YS, Chen YL, Chuang SF, Wu CM, Wei PJ, Han CF, Lin JC, Chang HT. Riboflavin-ultraviolet-A-induced collagen cross-linking treatments in improving dentin bonding. Dent Mater 2013; 29:682-92. [PMID: 23582694 DOI: 10.1016/j.dental.2013.03.015] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Revised: 10/15/2012] [Accepted: 03/14/2013] [Indexed: 11/17/2022]
Abstract
OBJECTIVES To evaluate the collagen cross-linkers, riboflavin-ultraviolet-A (RF/UVA) and glutaraldehyde, with regard to their efficacy in cross-linking the dentinal collagen and improving dentin bonding. METHODS Glutaraldehyde and different RF/UVA protocols (0.1%RF/1-minUV, 0.1%RF/2-minUV, and 1%RF/1-minUV) were first evaluated by gel electrophoresis to determine their abilities of collagen cross-linking. The mechanical properties of acid-etched dentin receiving these cross-linking treatments were examined in either dry or wet condition by a nanoindentation test. Fifteen teeth with exposed occlusal dentin received the microtensile bond strength (μTBS) test. The teeth were primed either with RF/UVA or glutaraldehyde, followed by adhesive treatment and composite restorations, and then cut into resin-dentin microbeams. Half of the microbeams received the μTBS test after 24h, and the other half received test after 5000 thermocycles. Nanoleakage at the bond interface was examined under TEM. The alignments of collagen fibrils in the hybrid layers were also defined by an image analysis. RESULTS Gel electrophoresis showed that glutaraldehyde induced strong collagen gelation, while RF/UVA generated milder collagen cross-linking. Glutaraldehyde, 0.1%RF/2-min-UVA, and 1%RF/1-minUV showed higher stiffness compared to untreated and 0.1%RF/1-minUV in wet condition. All the crosslinking treatments improved early μTBS, but 0.1%RF/2-minUVA treatment maintained high μTBS after theromocycles. Under TEM, glutaraldehyde-treated dentin showed dense and enclosed collagen network on the adhesive interface. 0.1%RF/2-minUVA showed the least nanoleakage, and this could be associated with the suspended collagen fibrils in the hybrid layer. SIGNIFICANCE 0.1%RF/2-minUVA treatment enhanced resin-dentin bond possibly through enhancing the stiffness and maintaining the expanding collagen matrix in the hybrid layer.
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Affiliation(s)
- Yung-Show Chiang
- Institute of Oral Medicine, National Cheng Kung University, Tainan, Taiwan
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Biomechanical properties of corneal tissue after ultraviolet-A–riboflavin crosslinking. J Cataract Refract Surg 2013; 39:451-62. [DOI: 10.1016/j.jcrs.2013.01.026] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Revised: 10/22/2012] [Accepted: 11/09/2012] [Indexed: 11/23/2022]
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Meek KM, Hayes S. Corneal cross-linking - a review. Ophthalmic Physiol Opt 2013; 33:78-93. [DOI: 10.1111/opo.12032] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2012] [Accepted: 01/10/2013] [Indexed: 11/26/2022]
Affiliation(s)
- Keith M Meek
- Structural Biophysics Group; School of Optometry and Vision Sciences; Cardiff University; Cardiff; UK
| | - Sally Hayes
- Structural Biophysics Group; School of Optometry and Vision Sciences; Cardiff University; Cardiff; UK
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Zhang Y, Mao X, Schwend T, Littlechild S, Conrad GW. Resistance of corneal RFUVA–cross-linked collagens and small leucine-rich proteoglycans to degradation by matrix metalloproteinases. Invest Ophthalmol Vis Sci 2013; 54:1014-25. [PMID: 23322569 DOI: 10.1167/iovs.12-11277] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Extracellular matrix metalloproteinases (MMPs) are thought to play a crucial role in corneal degradation associated with the pathological progression of keratoconus. Currently, corneal cross-linking by riboflavin and ultraviolet A (RFUVA) has received significant attention for treatment of keratoconus. However, the extent to which MMPs digest cross-linked collagen and small leucine-rich proteoglycans (SLRPs) remains unknown. In this study, the resistance of RFUVA-cross-linked collagens and SLRPs to MMPs has been investigated. METHODS To investigate the ability of MMPs to digest cross-linked collagen and SLRPs, a model reaction system using purified collagen type I, type IV, and nonglycosylated, commercially available recombinant SLRPs, keratocan, lumican, mimecan, decorin, and biglycan in solution in vitro has been compared using reactions inside an intact bovine cornea, ex vivo. RESULTS Our data demonstrate that corneal cross-linked collagen type I and type IV are resistant to cleavage by MMP-1, MMP-2, MMP-9, and MMP-13, whereas non-cross-linked collagen I, IV, and natively glycosylated SLRPs are susceptible to degradation by MMPs. In addition, both cross-linked SLRPs themselves and cross-linked polymers of SLRPs and collagen appear able to resist degradation. These results suggest that the interactions between SLRPs and collagen caused by RFUVA protect both SLRPs and collagen fibrils from cleavage by MMPs. CONCLUSIONS A novel approach for understanding the biochemical mechanism whereby RFUVA cross-linking stops keratoconus progression has been achieved.
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Affiliation(s)
- Yuntao Zhang
- Division of Biology, Kansas State University, Manhattan, Kansas 66506-4901, USA.
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Effects of Collagen Cross-Linking on the Interlamellar Cohesive Strength of Porcine Cornea. Cornea 2013; 32:169-73. [DOI: 10.1097/ico.0b013e318264ee6a] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Raiskup F, Spoerl E. Corneal crosslinking with riboflavin and ultraviolet A. I. Principles. Ocul Surf 2013; 11:65-74. [PMID: 23583042 DOI: 10.1016/j.jtos.2013.01.002] [Citation(s) in RCA: 175] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/01/2012] [Indexed: 01/20/2023]
Abstract
Changes in the biomechanical properties of the human cornea play an important role in the pathogenesis of corneal ectatic diseases. Biomechanical investigation shows significant differences between human ectatic corneas and normal corneas, including decreased stiffness and reduction of collagen crosslinks in the ectatic cornea. Induction of crosslinks is a well-established procedure in polymer chemistry to increase the elastic modulus of materials. Crosslinking (CXL) in connective tissue can occur during aging and as a side effect of diabetes mellitus. CXL has been used medically to increase stability and reduce the biodegradation of collagen-based biomaterials for bioprostheses. CXL of the cornea using riboflavin and UVA light with a wavelength of 370 nm and a dosage of 5.4 J/cm² is a new approach that increases the mechanical and biochemical stability of stromal tissue. This technique combines the principles of CXL (chemical and nonenzymatic) and the biochemical mechanisms of photo-oxidative CXL with riboflavin as a photosensitizer. In this review, the enrichment of riboflavin in the stroma by standard (epi-off) and transepithelial (epi-on) CXL is discussed. The theoretical and experimental measurements of the absorption of UV light explain the stronger CXL effect in the anterior stroma and its importance for the prevention of damage to the endothelial cells. UV devices are described. Changes of the physical properties after CXL, as well as the cellular changes, are discussed. From these basic investigations, treatment parameters for effective and safe CXL are identified.
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Affiliation(s)
- Frederik Raiskup
- Department of Ophthalmology, Carl Gustav Carus University Hospital, Dresden, Germany.
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Structural response of human corneal and scleral tissues to collagen cross-linking treatment with riboflavin and ultraviolet A light. Lasers Med Sci 2012. [DOI: 10.1007/s10103-012-1237-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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The Effect of Riboflavin–UV-A Treatment on Corneal Limbal Epithelial Cells—A Study on Human Cadaver Eyes. Cornea 2012; 31:1052-9. [DOI: 10.1097/ico.0b013e3182498902] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Knox Cartwright NE, Tyrer JR, Marshall J. In vitro quantification of the stiffening effect of corneal cross-linking in the human cornea using radial shearing speckle pattern interferometry. J Refract Surg 2012; 28:503-8. [PMID: 22833877 DOI: 10.3928/1081597x-20120613-01] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE To quantify the magnitude of the stiffening effect of corneal cross-linking (CXL) by studying intact human corneas exposed to physiological pressure transients. METHODS Nine organ-cultured human corneas mounted in artificial anterior chambers were studied. A radial shearing speckle pattern interferometer was used to measure changes in corneal strain following an increase in artificial anterior chamber pressure from 15.0 to 15.5 mmHg before and after treatment. Measurements were taken from all corneas with their epithelium intact before all underwent epithelial debridement. Three specimens were used as controls and did not receive any further treatment; three underwent riboflavin/ultraviolet A (UVA) CXL using 30 minutes of 370-nm irradiation at 3 mW/cm2 following epithelial removal and saturation with 0.1% riboflavin; and three were fixed with the cross-linking agent 2.5% glutaraldehyde. Strain measurements were repeated after these treatments. Young's moduli of individual corneas were calculated by mathematical analysis. RESULTS Mean donor age was 81.7 years. Before treatment, the mean Young's moduli of the control, riboflavin/UVA CXL, and glutaraldehyde-fixed corneas did not differ significantly: 0.46±0.03, 0.48±0.03, and 0.47±0.03 MPa, respectively. Following treatment these values changed to 0.46±0.2, 2.06±0.22, and 3.48±0.41 MPa, respectively. In proportional terms, this was equivalent to an increase in corneal Young's modulus by a factor of 4.3 (P<.05) following riboflavin/UVA CXL and 7.3 (P<.05) after glutaraldehyde fixation. CONCLUSIONS Riboflavin-UVA CXL increases the stiffness of organ-cultured corneas by a factor of more than four. This finding quantifies the efficacy of CXL in a physiologic configuration.
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Safety and efficacy of epithelium-on corneal collagen cross-linking using a multifactorial approach to achieve proper stromal riboflavin saturation. J Ophthalmol 2012; 2012:498435. [PMID: 22900147 PMCID: PMC3413959 DOI: 10.1155/2012/498435] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Accepted: 06/10/2012] [Indexed: 11/18/2022] Open
Abstract
Purpose. To evaluate the efficacy and safety of epithelium-on corneal collagen cross-linking (CXL) using a multifactorial approach to achieve proper stromal riboflavin saturation. Methods. This non-randomized retrospective study comprised 61 eyes with progressive keratoconus treated with epithelium-on CXL. Chemical epithelial penetration enhancement (benzalkonium chloride-containing local medication and hypotonic riboflavin solution), mechanical disruption of the superficial epithelium, and prolongation of the riboflavin-induction time until verification of stromal saturation were used before the UVA irradiation. Uncorrected and corrected distance visual acuity (UDVA, CDVA), refraction, corneal topography, and aberrometry were evaluated at baseline and at 1, 3, 6, and 12 months postoperative. Results. At 12-month, UDVA and CDVA improved significantly. None of the eyes lost lines of CDVA, while 27.4% of the eyes gained 2 or more lines. Mean spherical equivalent decreased by 0.74 D, and mean cylindrical reduction was 1.15 D. Irregularity index and asymmetry from Scheimpflug-based topography and Max-K at the location of cone from Placido-based topography showed a significant decrease. Higher-order-aberration data demonstrated a slight reduction in odd-order aberrations S 3, 5,7 (P = 0.04). Postoperative pain without other complications was recorded. Conclusion. Epithelium-on CXL with our novel protocol appeared to be safe and effective in the treatment of progressive keratoconus.
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Dahl BJ, Spotts E, Truong JQ. Corneal collagen cross-linking: an introduction and literature review. ACTA ACUST UNITED AC 2012; 83:33-42. [PMID: 22153823 DOI: 10.1016/j.optm.2011.09.011] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Revised: 02/22/2011] [Accepted: 09/08/2011] [Indexed: 10/14/2022]
Abstract
BACKGROUND This literature review analyzes the scientific evidence available regarding corneal collagen cross-linking (CXL) as a treatment option for progressive keratectasia. METHODS A literature search was performed using dates from 1990 to August 2010 regarding CXL Specific areas of focus for the literature review include safety and efficacy of the procedure as a stand-alone treatment or when used in conjunction with Intacs® corneal implants (Addition Technology™) or photorefractive keratectomy (PRK). RESULTS A total of 50 clinical trials and studies were identified, 20 of which met the inclusion criteria. Results of the included literature support the conclusion that CXL is a safe and efficacious treatment for progressive keratectasia. The results of CXL alone have shown stabilization or improvement in the maximum keratometry readings, best-corrected visual acuity, uncorrected visual acuity, and spherical and cylinder refractive measurements. CXL has been shown to enhance the effects of Intacs and has been proven successful when used in conjunction with PRK. CONCLUSION CXL is an effective treatment for limiting the progression of keratectasia, thus reducing the need for penetrating keratoplasty. CXL has a similar side-effect profile and similar risk level as PRK.
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Affiliation(s)
- Brandon J Dahl
- Keller Army Community Hospital, West Point, and State University of New York, College of Optometry, New York, NY, USA.
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Mazzotta C, Caporossi T, Denaro R, Bovone C, Sparano C, Paradiso A, Baiocchi S, Caporossi A. Morphological and functional correlations in riboflavin UV A corneal collagen cross-linking for keratoconus. Acta Ophthalmol 2012; 90:259-65. [PMID: 20456255 DOI: 10.1111/j.1755-3768.2010.01890.x] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
PURPOSE To investigate the correlations between corneal structural modifications assessed by in vivo corneal confocal microscopy with visual function [uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA)] and morphological data (corneal topography, pachymetry, elevation analysis) after riboflavin UV A corneal collagen cross-linking (CXL) for the stabilization of progressive keratoconus. METHODS Forty-four eyes with progressive keratoconus were enrolled in the Siena Eye Cross Study (prospective nonrandomized phase II open trial). All eyes underwent Riboflavin UV A CXL. Preoperative and postoperative evaluation comprised: UCVA, BSCVA, optical pachymetry (Visante OCT, Zeiss, Germany), corneal topography (CSO, Florence, Italy) and tomography (Orbscan IIz; B&L, Rochester, NY, USA) and in vivo confocal microscopy (Heidelberg Retina Tomograph II; Rostock, Heidelberg Gmbh, Germany). Examinations were performed preoperatively 6 months and one day before treatment and at 1, 3, 6 and 12 months of follow-up. RESULTS In vivo corneal confocal microscopy showed time-dependent postoperative epithelial and stromal modifications after cross-linking. Epithelial thinning associated with stromal oedema and keratocytes apoptosis explained initial tendency towards slightly reduced VA and more glare one month postoperatively in 70% of eyes. Furthermore, a statistically not significant early worsening of topographic mean K values was observed. Orbscan II analysis significantly underestimated pachymetric values after treatment. Pachymetric underestimation was rectified by high-resolution optical pachymetry provided by the Visante OCT system. After the third post-CXL month, epithelial thickening, disappearance of oedema and new collagen compaction recorded by in vivo corneal confocal microscopy explained the improvements in visual performance during the follow-up. Changes in stromal reflectivity and collagen compaction observed by in vivo confocal microscopy were associated with corneal flattening and reduction in anterior elevation values recorded by differential topographic analysis. CONCLUSION Corneal structural changes assessed by in vivo corneal confocal microscopy demonstrated significant correlations with visual function (UCVA and BSCVA) and morphological (corneal topography, pachymetry, elevation analysis) findings recorded after riboflavin-UV A-induced CXL.
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Affiliation(s)
- Cosimo Mazzotta
- Department of Ophthalmology, Siena University, Siena, Italy.
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Jung GB, Lee HJ, Kim JH, Lim JI, Choi S, Jin KH, Park HK. Effect of cross-linking with riboflavin and ultraviolet A on the chemical bonds and ultrastructure of human sclera. JOURNAL OF BIOMEDICAL OPTICS 2011; 16:125004. [PMID: 22191917 DOI: 10.1117/1.3662458] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
This study examined the effect of the cross-linking with riboflavin-ultraviolet A (UVA) irradiation on the chemical bonds and ultrastructural changes of human sclera tissues using Raman spectroscopy and atomic force microscopy (AFM). Raman spectroscopy of the normal and cross-linked human sclera tissue revealed different types of the riboflavin-UVA and collagen interactions, which could be identified from their unique peaks, intensity, and shape. Raman spectroscopy can prove to be a powerful tool for examining the chemical bond of collagenous tissues at the molecular level. After riboflavin-UVA treatment, unlike a regular parallel arrangement of normal collagen fibrils, the AFM image revealed interlocking arrangements of collagen fibrils. The observed changes in the surface topography of the collagen fibrils, as well as in their chemical bonds in the sclera tissue, support the formation of interfibrilar cross-links in sclera tissues.
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Affiliation(s)
- Gyeong-Bok Jung
- Kyung Hee University, College of Medicine, Department of Biomedical Engineering & Healthcare Industry Research Institute, 1 Hoegi-dong, Dongdaemun-gu, Seoul 130-701, Republic of Korea
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