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Wu D, Lim DKA, Lim BXH, Wong N, Hafezi F, Manotosh R, Lim CHL. Corneal Cross-Linking: The Evolution of Treatment for Corneal Diseases. Front Pharmacol 2021; 12:686630. [PMID: 34349648 PMCID: PMC8326410 DOI: 10.3389/fphar.2021.686630] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2021] [Accepted: 07/05/2021] [Indexed: 01/31/2023] Open
Abstract
Corneal cross-linking (CXL) using riboflavin and ultraviolet A (UVA) light has become a useful treatment option for not only corneal ectasias, such as keratoconus, but also a number of other corneal diseases. Riboflavin is a photoactivated chromophore that plays an integral role in facilitating collagen crosslinking. Modifications to its formulation and administration have been proposed to overcome shortcomings of the original epithelium-off Dresden CXL protocol and increase its applicability across various clinical scenarios. Hypoosmolar riboflavin formulations have been used to artificially thicken thin corneas prior to cross-linking to mitigate safety concerns regarding the corneal endothelium, whereas hyperosmolar formulations have been used to reduce corneal oedema when treating bullous keratopathy. Transepithelial protocols incorporate supplementary topical medications such as tetracaine, benzalkonium chloride, ethylenediaminetetraacetic acid and trometamol to disrupt the corneal epithelium and improve corneal penetration of riboflavin. Further assistive techniques include use of iontophoresis and other wearable adjuncts to facilitate epithelium-on riboflavin administration. Recent advances include, Photoactivated Chromophore for Keratitis-Corneal Cross-linking (PACK-CXL) for treatment of infectious keratitis, customised protocols (CurV) utilising riboflavin coupled with customised UVA shapes to induce targeted stiffening have further induced interest in the field. This review aims to examine the latest advances in riboflavin and UVA administration, and their efficacy and safety in treating a range of corneal diseases. With such diverse riboflavin delivery options, CXL is well primed to complement the armamentarium of therapeutic options available for the treatment of a variety of corneal diseases.
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Affiliation(s)
- Duoduo Wu
- Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Dawn Ka-Ann Lim
- Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.,Department of Ophthalmology, National University Health System, Singapore, Singapore
| | - Blanche Xiao Hong Lim
- Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.,Department of Ophthalmology, National University Health System, Singapore, Singapore
| | - Nathan Wong
- Royal Victorian Eye Hospital, Melbourne, VIC, Australia
| | - Farhad Hafezi
- Ocular Cell Biology Group, Center for Applied Biotechnology and Molecular Medicine, University of Zurich, Zurich, Switzerland.,ELZA Institute, Dietikon, Switzerland.,Faculty of Medicine, University of Geneva, Geneva, Switzerland.,Ophthalmology, USC Roski Eye Institute, Los Angeles, CA, United States.,Ophthalmology, Wenzhou Medical University, Wenzhou, China
| | - Ray Manotosh
- Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.,Department of Ophthalmology, National University Health System, Singapore, Singapore
| | - Chris Hong Long Lim
- Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.,Department of Ophthalmology, National University Health System, Singapore, Singapore.,Singapore Eye Research Institute, Singapore, Singapore.,School of Optometry and Vision Science, University of New South Wales, Sydney, NSW, Australia
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Bradford S, Mikula E, Kim SW, Xie Y, Juhasz T, Brown DJ, Jester JV. Nonlinear Optical Corneal Crosslinking, Mechanical Stiffening, and Corneal Flattening Using Amplified Femtosecond Pulses. Transl Vis Sci Technol 2019; 8:35. [PMID: 31890347 PMCID: PMC6917096 DOI: 10.1167/tvst.8.6.35] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Accepted: 10/06/2019] [Indexed: 12/14/2022] Open
Abstract
PURPOSE We have shown that nonlinear optical corneal crosslinking (NLO CXL) and stiffening can be achieved in ex vivo rabbit corneas using an 80-MHz, 760-nm femtosecond (FS) laser, however the required power was beyond the American National Standard Institute limit. The purpose of this study was to test the efficacy of amplified FS pulses to perform CXL to reduce power by increasing pulse energy. METHODS A variable numerical aperture laser scanning delivery system was coupled to a 1030-nm laser with a noncollinear optical parametric amplifier to generate 760 nm, 50 to 150 kHz amplified FS pulses with 79.5-μm axial and 2.9-μm lateral two-photon focal volume. Ex vivo rabbit corneas received NLO CXL, and effectiveness was assessed by measuring collagen autofluorescence (CAF) and mechanical stiffening. NLO CXL was also performed in 14 live rabbits, and changes in corneal topography were measured using an Orbscan. RESULTS Amplified pulses (0.3 μJ) generated significant CAF that increased logarithmically with decreasing scan speed; achieving equivalent CAF to UVA CXL at 15.5 mm/s. Indentation testing detected a 62% increase in stiffness compared to control, and corneal topography measurements revealed a significant decrease of 1.0 ± 0.8 diopter by 1 month (P < 0.05). CONCLUSIONS These results show that NLO CXL using amplified pulses can produce corneal collagen CXL comparable to UVA CXL. TRANSLATIONAL RELEVANCE NLO CXL using amplified pulses can produce corneal CXL comparable to UVA CXL, suggesting a potential clinical application in which NLO CXL can be used to perform personalized crosslinking for treatment of refractive errors and keratoconus.
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Affiliation(s)
- Samantha Bradford
- University of California, Irvine, Department of Ophthalmology and Biomedical Engineering, Irvine, CA, USA
| | - Eric Mikula
- University of California, Irvine, Department of Ophthalmology and Biomedical Engineering, Irvine, CA, USA
| | - Sun Woong Kim
- University of California, Irvine, Department of Ophthalmology and Biomedical Engineering, Irvine, CA, USA
- Yonsei University, Wonju College of Medicine, Department of Ophthalmology, Wonju, South Korea
| | - Yilu Xie
- University of California, Irvine, Department of Ophthalmology and Biomedical Engineering, Irvine, CA, USA
| | - Tibor Juhasz
- University of California, Irvine, Department of Ophthalmology and Biomedical Engineering, Irvine, CA, USA
| | - Donald J. Brown
- University of California, Irvine, Department of Ophthalmology and Biomedical Engineering, Irvine, CA, USA
| | - James V. Jester
- University of California, Irvine, Department of Ophthalmology and Biomedical Engineering, Irvine, CA, USA
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Bradford SM, Mikula ER, Juhasz T, Brown DJ, Jester JV. Collagen fiber crimping following in vivo UVA-induced corneal crosslinking. Exp Eye Res 2018; 177:173-180. [PMID: 30118656 PMCID: PMC6911705 DOI: 10.1016/j.exer.2018.08.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 08/03/2018] [Accepted: 08/13/2018] [Indexed: 02/03/2023]
Abstract
The purpose of this study was to measure collagen fiber crimping (CFC) using nonlinear optical imaging of second harmonic generated (SHG) signals to determine the effects of UVA-riboflavin induced corneal collagen crosslinking (UVA CXL) on collagen structure. Two groups, four rabbits each, were treated in the right eye with standard UVA CXL. In vivo confocal microscopy was performed at 1, 2, and 4 weeks after treatment for the first group and up to three months for the second group to measure epithelial/stromal thickness and corneal haze during recovery. Rabbits were sacrificed at one and three months, respectively, and their corneas fixed under pressure. Regions of crosslinking were identified by the presence of collagen autofluorescence (CAF) and then collagen structure was imaged using SHG microscopy. The degree of CFC was determined by measuring the percentage difference between the length of the collagen fiber and the linear distance traveled. CFC was measured in the central anterior and posterior CXL region, the peripheral non-crosslinked region in the same cornea, and the central cornea of the non-crosslinked contralateral eye. No change in corneal thickness was detected after one month, however the stromal thickness surpassed its original baseline thickness at three months by 25.9 μm. Corneal haze peaked at one month and then began to clear. Increased CAF was detected in all CXL corneas, localized to the anterior stroma and extending to 42.4 ± 3.4% and 47.7 ± 7.6% of the corneal thickness at one and three months. There was a significant (P < 0.05) reduction in CFC in the CAF region in all eyes averaging 1.007 ± 0.006 and 1.009 ± 0.005 in one and three month samples compared to 1.017 ± 0.04 and 1.016 ± 0.06 for controls. These results indicate that there is a significant reduction in collagen crimping following UVA CXL of approximately 1%. One possible explanation for this loss of crimping could be shortening of the collagen fibers over the CXL region.
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Affiliation(s)
- Samantha M Bradford
- Biomedical Engineering, University of California, Irvine, Irvine, CA, United States.
| | - Eric R Mikula
- Ophthalmology, University of California, Irvine, Irvine, CA, United States.
| | - Tibor Juhasz
- Biomedical Engineering, University of California, Irvine, Irvine, CA, United States; Ophthalmology, University of California, Irvine, Irvine, CA, United States.
| | - Donald J Brown
- Ophthalmology, University of California, Irvine, Irvine, CA, United States.
| | - James V Jester
- Biomedical Engineering, University of California, Irvine, Irvine, CA, United States; Ophthalmology, University of California, Irvine, Irvine, CA, United States.
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