1
|
Guimarães P, Morgado M, Batista A. On the quantitative analysis of lamellar collagen arrangement with second-harmonic generation imaging. BIOMEDICAL OPTICS EXPRESS 2024; 15:2666-2680. [PMID: 38633085 PMCID: PMC11019681 DOI: 10.1364/boe.516817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/27/2023] [Revised: 02/23/2024] [Accepted: 02/27/2024] [Indexed: 04/19/2024]
Abstract
Second harmonic generation (SHG) allows for the examination of collagen structure in collagenous tissues. Collagen is a fibrous protein found in abundance in the human body, present in bones, cartilage, the skin, and the cornea, among other areas, providing structure, support, and strength. Its structural arrangement is deeply intertwined with its function. For instance, in the cornea, alterations in collagen organization can result in severe visual impairments. Using SHG imaging, various metrics have demonstrated the potential to study collagen organization. The discrimination between healthy, keratoconus, and crosslinked corneas, assessment of injured tendons, or the characterization of breast and ovarian tumorous tissue have been demonstrated. Nevertheless, these metrics have not yet been objectively evaluated or compared. A total of five metrics were identified and implemented from the literature, and an additional approach adapted from texture analysis was proposed. In this study, we analyzed their effectiveness on a ground-truth set of artificially generated fibrous images. Our investigation provides the first comprehensive assessment of the performance of multiple metrics, identifying both the strengths and weaknesses of each approach and providing valuable insights for future applications of SHG imaging in medical diagnostics and research.
Collapse
Affiliation(s)
- Pedro Guimarães
- Coimbra Institute for Biomedical Imaging and Translational Research (CIBIT), Institute for Nuclear Sciences Applied to Health (ICNAS), University of Coimbra, Coimbra, Portugal
| | - Miguel Morgado
- Coimbra Institute for Biomedical Imaging and Translational Research (CIBIT), Institute for Nuclear Sciences Applied to Health (ICNAS), University of Coimbra, Coimbra, Portugal
- Department of Physics, Faculty of Science and Technology, University of Coimbra, Coimbra, Portugal
| | - Ana Batista
- Coimbra Institute for Biomedical Imaging and Translational Research (CIBIT), Institute for Nuclear Sciences Applied to Health (ICNAS), University of Coimbra, Coimbra, Portugal
- Department of Physics, Faculty of Science and Technology, University of Coimbra, Coimbra, Portugal
- Centre for Innovative Biomedicine and Biotechnology (CIBB), Faculty of Medicine, University of Coimbra, Coimbra, Portugal
| |
Collapse
|
2
|
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.
Collapse
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
| |
Collapse
|
3
|
Jeon H, Harvey M, Cisek R, Bennett E, Tokarz D. Characterization of pathological stomach tissue using polarization-sensitive second harmonic generation microscopy. BIOMEDICAL OPTICS EXPRESS 2023; 14:5376-5391. [PMID: 37854565 PMCID: PMC10581783 DOI: 10.1364/boe.500335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Revised: 08/16/2023] [Accepted: 09/09/2023] [Indexed: 10/20/2023]
Abstract
Alterations in collagen ultrastructure between human gastric adenocarcinoma and normal gastric tissue were investigated using polarization-resolved second harmonic generation (PSHG) microscopy. Cylindrical and trigonal symmetries were assumed to extract quantitative PSHG parameters, ρ, κ and S, from each image pixel. Statistically significant variations in these values were observed for gastric adenocarcinoma, indicating a higher disorder of collagen. Numerical focal volume simulations of crossing fibrils indicate increased S parameter is due to more intersecting collagen fibrils of varying diameters. These parameters were also able to distinguish between different grades of gastric adenocarcinoma indicating that PSHG may be useful for automated cancer diagnosis.
Collapse
Affiliation(s)
- Hwanhee Jeon
- Department of Chemistry, Saint Mary’s University, 923 Robie Street, Halifax, Nova Scotia, B3H 3C3, Canada
| | - MacAulay Harvey
- Department of Chemistry, Saint Mary’s University, 923 Robie Street, Halifax, Nova Scotia, B3H 3C3, Canada
| | - Richard Cisek
- Department of Chemistry, Saint Mary’s University, 923 Robie Street, Halifax, Nova Scotia, B3H 3C3, Canada
| | - Elisha Bennett
- Department of Chemistry, Saint Mary’s University, 923 Robie Street, Halifax, Nova Scotia, B3H 3C3, Canada
| | - Danielle Tokarz
- Department of Chemistry, Saint Mary’s University, 923 Robie Street, Halifax, Nova Scotia, B3H 3C3, Canada
| |
Collapse
|
4
|
Batista A, Guimarães P, Domingues JP, Quadrado MJ, Morgado AM. Two-Photon Imaging for Non-Invasive Corneal Examination. SENSORS (BASEL, SWITZERLAND) 2022; 22:9699. [PMID: 36560071 PMCID: PMC9783858 DOI: 10.3390/s22249699] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Revised: 12/02/2022] [Accepted: 12/04/2022] [Indexed: 06/17/2023]
Abstract
Two-photon imaging (TPI) microscopy, namely, two-photon excited fluorescence (TPEF), fluorescence lifetime imaging (FLIM), and second-harmonic generation (SHG) modalities, has emerged in the past years as a powerful tool for the examination of biological tissues. These modalities rely on different contrast mechanisms and are often used simultaneously to provide complementary information on morphology, metabolism, and structural properties of the imaged tissue. The cornea, being a transparent tissue, rich in collagen and with several cellular layers, is well-suited to be imaged by TPI microscopy. In this review, we discuss the physical principles behind TPI as well as its instrumentation. We also provide an overview of the current advances in TPI instrumentation and image analysis. We describe how TPI can be leveraged to retrieve unique information on the cornea and to complement the information provided by current clinical devices. The present state of corneal TPI is outlined. Finally, we discuss the obstacles that must be overcome and offer perspectives and outlooks to make clinical TPI of the human cornea a reality.
Collapse
Affiliation(s)
- Ana Batista
- Coimbra Institute for Biomedical Imaging and Translational Research (CIBIT), University of Coimbra, 3000-548 Coimbra, Portugal
- Institute for Nuclear Sciences Applied to Health (ICNAS), University of Coimbra, 3000-548 Coimbra, Portugal
- Department of Physics, Faculty of Science and Technology, University of Coimbra, 3004-516 Coimbra, Portugal
| | - Pedro Guimarães
- Coimbra Institute for Biomedical Imaging and Translational Research (CIBIT), University of Coimbra, 3000-548 Coimbra, Portugal
- Institute for Nuclear Sciences Applied to Health (ICNAS), University of Coimbra, 3000-548 Coimbra, Portugal
| | - José Paulo Domingues
- Coimbra Institute for Biomedical Imaging and Translational Research (CIBIT), University of Coimbra, 3000-548 Coimbra, Portugal
- Institute for Nuclear Sciences Applied to Health (ICNAS), University of Coimbra, 3000-548 Coimbra, Portugal
- Department of Physics, Faculty of Science and Technology, University of Coimbra, 3004-516 Coimbra, Portugal
| | - Maria João Quadrado
- Department of Ophthalmology, Centro Hospitalar e Universitário de Coimbra, 3004-561 Coimbra, Portugal
- Coimbra Institute for Clinical and Biomedical Research (iCBR), Faculty of Medicine, University of Coimbra, 3000-548 Coimbra, Portugal
| | - António Miguel Morgado
- Coimbra Institute for Biomedical Imaging and Translational Research (CIBIT), University of Coimbra, 3000-548 Coimbra, Portugal
- Institute for Nuclear Sciences Applied to Health (ICNAS), University of Coimbra, 3000-548 Coimbra, Portugal
- Department of Physics, Faculty of Science and Technology, University of Coimbra, 3004-516 Coimbra, Portugal
| |
Collapse
|
5
|
Danielewska ME, Antonczyk A, Andrade De Jesus D, Rogala MM, Blonska A, Cwirko M, Kielbowicz Z, Iskander DR. Corneal Optical Coherence Tomography Speckle in Crosslinked and Untreated Rabbit Eyes in Response to Elevated Intraocular Pressure. Transl Vis Sci Technol 2021; 10:2. [PMID: 34003977 PMCID: PMC8088219 DOI: 10.1167/tvst.10.5.2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Purpose To ascertain the influence of intraocular pressure (IOP) on corneal optical coherence tomography (OCT) speckle in untreated and ultraviolet A–riboflavin induced corneal collagen crosslinked rabbit eyes. Methods Left corneas of eight rabbits were de-epithelialized and crosslinked by applying riboflavin and 30-minute ultraviolet A light exposure. After enucleation (6 months after treatment), each eyeball (treated and untreated) was mounted in a measurement setup, in which IOP was increased from 15 to 45 mm Hg in steps of 5 mm Hg. At each IOP value, single B-scans of the central cornea were acquired three times with the spectral-domain OCT Copernicus-HR. Then, three regions of interest, including the anterior, posterior, and entire corneal stroma, were automatically extracted. Five different probability distributions were used as a model for the corneal speckle and the one with the best goodness of fit was chosen for further analysis. Results The generalized gamma distribution achieved the best goodness of fit and its scale (a) and shape (v) parameters statistically significantly changed with increasing IOP in the three regions of analysis (two-way repeated measures analysis of variance, all P < 0.05). The statistically significant difference between untreated and crosslinked eyes was observed for the shape parameters of the posterior and entire corneal stroma. Conclusions Corneal OCT speckle is influenced by IOP and shows to be significantly different in untreated and crosslinked eyes. Corneal OCT speckle analysis has the potential to be indirectly used for assessing changes in corneal stroma in ex vivo and in vivo studies. Translational Relevance Investigation of corneal OCT speckle statistics can offer additional diagnostic biomarkers related to changes in the corneal stroma after ocular surgeries.
Collapse
Affiliation(s)
- Monika E Danielewska
- Wrocław University of Science and Technology, Department of Biomedical Engineering, Wrocław, Poland
| | - Agnieszka Antonczyk
- Wrocław University of Environmental and Life Sciences, Department of Surgery, Faculty of Veterinary Medicine, Wrocław, Poland
| | - Danilo Andrade De Jesus
- Erasmus University Medical Center, Department of Radiology and Nuclear Medicine, Biomedical Imaging Group Rotterdam, Rotterdam, The Netherlands
| | - Maja M Rogala
- Wrocław University of Science and Technology, Department of Mechanics, Materials and Biomedical Engineering, Wrocław, Poland
| | - Anna Blonska
- Ophthalmology Clinical Centre SPEKTRUM, Wrocław, Poland
| | - Marek Cwirko
- Ophthalmology Clinical Centre SPEKTRUM, Wrocław, Poland
| | - Zdzislaw Kielbowicz
- Wrocław University of Environmental and Life Sciences, Department of Surgery, Faculty of Veterinary Medicine, Wrocław, Poland
| | - D Robert Iskander
- Wrocław University of Science and Technology, Department of Biomedical Engineering, Wrocław, Poland
| |
Collapse
|
6
|
James DS, Brereton CJ, Davies DE, Jones MG, Campagnola PJ. Examining lysyl oxidase-like modulation of collagen architecture in 3D spheroid models of idiopathic pulmonary fibrosis via second-harmonic generation microscopy. JOURNAL OF BIOMEDICAL OPTICS 2021; 26:JBO-210062R. [PMID: 34145800 PMCID: PMC8212879 DOI: 10.1117/1.jbo.26.6.066501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 05/27/2021] [Indexed: 06/12/2023]
Abstract
SIGNIFICANCE Idiopathic pulmonary fibrosis (IPF) patients have a poor prognosis with short lifespan following diagnosis as there are limited effective treatment options. Despite matrix stiffening being the hallmark of the disease there remains a lack of knowledge surrounding the underlying collagen alterations in the disease. Specifically, while increased collagen crosslinking has been implicated, the resulting effects on collagen macro/supramolecular changes have not been explored. AIM We sought to determine if second-harmonic generation (SHG) microscopy could characterize differences in the collagen architecture in 3D spheroid models of IPF grown under different crosslinking modulation conditions (promotion and inhibition). APPROACH We used SHG metrics based on the fiber morphology, relative SHG brightness, and macro/supramolecular structure by SHG polarization analyses to compare the structure of the IPF spheroids. RESULTS Comparison of the fiber morphology of the spheroids showed that the control group had the longest, straightest, and thickest fibers. The spheroids with crosslink enhancement and inhibition had the highest and lowest SHG conversion efficiencies, respectively, consistent with the resulting harmonophore density. SHG polarization analyses showed that the peptide pitch angle, alignment of collagen molecules, and overall chirality were altered upon crosslink modulation and were also consistent with reduced organization relative to the control group. CONCLUSIONS While no single SHG signature is associated with crosslinking, we show that the suite of metrics used here is effective in delineating alterations across the collagen architecture sizescales. The results largely mirror those of human tissues and demonstrate that the combination of 3D spheroid models and SHG analysis is a powerful approach for hypothesis testing the roles of operative cellular and molecular factors in IPF.
Collapse
Affiliation(s)
- Darian S. James
- University of Wisconsin–Madison, Department of Biomedical Engineering, Madison, Wisconsin, United States
| | - Christopher J. Brereton
- University of Southampton, Clinical and Experimental Sciences, Faculty of Medicine, Southampton, United Kingdom
- University Hospital Southampton, National Institute for Health Research Southampton Biomedical Research Centre, Southampton, United Kingdom
- University of Southampton, Institute for Life Sciences, Southampton, United Kingdom
| | - Donna E. Davies
- University of Southampton, Clinical and Experimental Sciences, Faculty of Medicine, Southampton, United Kingdom
- University Hospital Southampton, National Institute for Health Research Southampton Biomedical Research Centre, Southampton, United Kingdom
- University of Southampton, Institute for Life Sciences, Southampton, United Kingdom
| | - Mark G. Jones
- University of Southampton, Clinical and Experimental Sciences, Faculty of Medicine, Southampton, United Kingdom
- University Hospital Southampton, National Institute for Health Research Southampton Biomedical Research Centre, Southampton, United Kingdom
- University of Southampton, Institute for Life Sciences, Southampton, United Kingdom
| | - Paul J. Campagnola
- University of Wisconsin–Madison, Department of Biomedical Engineering, Madison, Wisconsin, United States
| |
Collapse
|
7
|
Bueno JM, Ávila FJ, Lorenzo-Martín E, Gallego-Muñoz P, Carmen Martínez-García M. Assessment of the corneal collagen organization after chemical burn using second harmonic generation microscopy. BIOMEDICAL OPTICS EXPRESS 2021; 12:756-765. [PMID: 33680540 PMCID: PMC7901323 DOI: 10.1364/boe.412819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 12/22/2020] [Indexed: 05/11/2023]
Abstract
The organization of the corneal stoma is modified due to different factors, including pathology, surgery or external damage. Here the changes in the organization of the corneal collagen fibers during natural healing after chemical burn are investigated using second harmonic generation (SHG) imaging. Moreover, the structure tensor (ST) was used as an objective tool for morphological analyses at different time points after burn (up to 6 months). Unlike control corneas that showed a regular distribution, the collagen pattern at 1 month of burn presented a non-organized arrangement. SHG signal levels noticeably decreased and individual fibers were hardly visible. Over time, the healing process led to a progressive re-organization of the fibers that could be quantified through the ST. At 6 months, the stroma distribution reached values similar to those of control eyes and a dominant direction of the fibers re-appeared. The present results show that SHG microscopy imaging combined with the ST method is able to objectively monitor the temporal regeneration of the corneal organization after chemical burn. Future implementations of this approach into clinically adapted devices would help to diagnose and quantify corneal changes, not only due to chemical damages, but also as a result of disease or surgical procedures.
Collapse
Affiliation(s)
- Juan M. Bueno
- Laboratorio de Óptica, Instituto Universitario de Investigación en Óptica y Nanofísica, Universidad de Murcia, Campus de Espinardo (Ed. 34), 30100 Murcia, Spain
| | | | - Elvira Lorenzo-Martín
- Dpto. Biología Celular, Histología y Farmacología, Facultad de Medicina, Universidad de Valladolid, 47005 Valladolid, Spain
| | - Patricia Gallego-Muñoz
- Dpto. Biología Celular, Histología y Farmacología, Facultad de Medicina, Universidad de Valladolid, 47005 Valladolid, Spain
| | - M. Carmen Martínez-García
- Dpto. Biología Celular, Histología y Farmacología, Facultad de Medicina, Universidad de Valladolid, 47005 Valladolid, Spain
| |
Collapse
|
8
|
Zeitoune AA, Bersanetti PA, Schor P, Erbes LA, Cesar CL, Adur J. Comparison of morphological changes of corneal collagen fibers treated with collagen crosslinking agents using second harmonic generation images. Int J Biol Macromol 2020; 165:346-353. [PMID: 32987082 DOI: 10.1016/j.ijbiomac.2020.09.147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 09/18/2020] [Accepted: 09/19/2020] [Indexed: 10/23/2022]
Abstract
Corneal cross-linking (CXL) is a common surgical procedure used to modify corneal biomechanics and stabilize keratoconus progression which is still under discussion. Its side effects, which are mostly related to anatomical unpredictability and stromal exposure, are the reason for the search for new CXL agents. In this work we have quantitatively evaluated the porcine corneal stroma architecture treated with collagen crosslinking agents such as riboflavin solutions and açai extract, using second harmonic generation microscopy. Aimed at evaluating the morphological changes in the corneal stroma after collagen crosslinking under a CXL chemical agent, a tubeness filter based Hessian matrix to obtain a 3D fiber characterization of the SHG images was applied. The results showed a curling effect and shortening of the collagen fibers treated with açai as compared to the control. They also showed a higher degree of clustering of the collagen fibers with larger empty spaces when compared to the other two groups. We believe that studies such as these presented in this paper are a good direct nondestructive and free labeling evaluation technique that allows the observation of morphologic features of corneas treated with new CXL agents.
Collapse
Affiliation(s)
- Angel A Zeitoune
- Instituto de Investigación y Desarrollo en Bioingeniería y Bioinformática (IBB), UNER, CONICET, Oro Verde, Entre Ríos, Argentina.
| | - Patrícia A Bersanetti
- Department of Biochemistry, Paulista School of Medicine, Federal University of São Paulo, São Paulo, Brazil
| | - Paulo Schor
- Department of Ophthalmology and Visual Sciences, Paulista School of Medicine, Federal University of São Paulo, São Paulo, Brazil
| | - Luciana A Erbes
- Instituto de Investigación y Desarrollo en Bioingeniería y Bioinformática (IBB), UNER, CONICET, Oro Verde, Entre Ríos, Argentina.
| | - Carlos L Cesar
- Department of Physics of Federal University of Ceara (UFC), Brazil; INFABiC - National Institute of Science and Technology on Photonics Applied to Cell Biology, Campinas, Brazil
| | - Javier Adur
- Instituto de Investigación y Desarrollo en Bioingeniería y Bioinformática (IBB), UNER, CONICET, Oro Verde, Entre Ríos, Argentina.
| |
Collapse
|
9
|
Seet LF, Chu SWL, Teng X, Toh LZ, Wong TT. Assessment of progressive alterations in collagen organization in the postoperative conjunctiva by multiphoton microscopy. BIOMEDICAL OPTICS EXPRESS 2020; 11:6495-6515. [PMID: 33282504 PMCID: PMC7687938 DOI: 10.1364/boe.403555] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 09/14/2020] [Accepted: 09/15/2020] [Indexed: 06/12/2023]
Abstract
Glaucoma filtration surgery (GFS) commonly fails due to excessive fibrosis. As collagen structure aberrations is implicated in adverse fibrotic progression, this study aims to uncover collagen organization alterations during postoperative scarring. Via quantitative second harmonic generation/two photon excitation multiphoton imaging, we reveal the scar development and phenotype in the mouse model of conjunctival scarring. We also show that multiphoton imaging corroborated the collagen ultrastructure anomaly characteristic of the SPARC-/- mouse postoperative conjunctiva. These data improve our understanding of postoperative conjunctival scarring and further enhance the utility of this model for the development of anti-fibrotic therapeutics for GFS.
Collapse
Affiliation(s)
- Li-Fong Seet
- Ocular Therapeutics and Drug Delivery, Singapore Eye Research Institute, Singapore
- Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Duke-NUS Medical School, Singapore
- Co-corresponding authors
| | - Stephanie W L Chu
- Ocular Therapeutics and Drug Delivery, Singapore Eye Research Institute, Singapore
| | | | - Li Zhen Toh
- Ocular Therapeutics and Drug Delivery, Singapore Eye Research Institute, Singapore
| | - Tina T Wong
- Ocular Therapeutics and Drug Delivery, Singapore Eye Research Institute, Singapore
- Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Duke-NUS Medical School, Singapore
- Glaucoma Service, Singapore National Eye Centre, Singapore
- Co-corresponding authors
| |
Collapse
|
10
|
Nonlinear optical crosslinking (NLO CXL) for correcting refractive errors. Exp Eye Res 2020; 199:108199. [PMID: 32846150 DOI: 10.1016/j.exer.2020.108199] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 08/18/2020] [Accepted: 08/19/2020] [Indexed: 11/21/2022]
Abstract
Ultraviolet A (UVA) light-based photoactivation of riboflavin (Rf) to induce corneal crosslinking (CXL) and mechanical stiffening is now a well-known treatment for corneal ectasia and Keratoconus that is being used in a topographically guided photorefractive intrastromal CXL (PiXL) procedure to treat low degrees of refractive errors. Alternative approaches for non-invasive treatment of refractive errors have also been proposed that use femtosecond lasers (FS) that provide much faster, more precise, and safer results than UVA CXL. One such treatment, nonlinear optical crosslinking (NLO CXL), has been able to replicate the effects of UVA CXL, while producing a smaller area of cellular damage and requiring a shorter procedure time. Unlike UVA CXL, the treatment volume of NLO CXL only occurs within the focal volume of the laser, which can be placed at any depth and scanned into any pattern for true topographically guided refractive correction. This review presents our experience with using FS lasers to photoactivate Rf and perform highly controlled corneal CXL that leads to mechanical stiffening and changes in corneal shape.
Collapse
|
11
|
Germann JA, Martínez-Enríquez E, Martínez-García MC, Kochevar IE, Marcos S. Corneal Collagen Ordering After In Vivo Rose Bengal and Riboflavin Cross-Linking. Invest Ophthalmol Vis Sci 2020; 61:28. [PMID: 32186674 PMCID: PMC7401826 DOI: 10.1167/iovs.61.3.28] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Purpose Photoactivated cornea collagen cross-linking (CXL) increases corneal stiffness by initiating formation of covalent bonds between stromal proteins. Because CXL depends on diffusion to distribute the photoinitiator, a gradient of CXL efficiency with depth is expected that may affect the degree of stromal collagen organization. We used second harmonic generation (SHG) microscopy to investigate the differences in stromal collagen organization in rabbit eyes after corneal CXL in vivo as a function of depth and time after surgery. Methods Rabbit corneas were treated in vivo with either riboflavin/UV radiation (UVX) or Rose Bengal/green light (RGX) and evaluated 1 and 2 months after CXL. Collagen fibers were imaged with a custom-built SHG scanning microscope through the central cornea (350 µm depth, 225 × 225 µm en face images). The order coefficient (OC), a metric for collagen organization, and total SHG signal were computed for each depth and compared between treatments. Results OC values of CXL-treated corneas were larger than untreated corneas by 27% and 20% after 1 month and 38% and 33% after 2 months for the RGX and UVX, respectively. RGX OC values were larger than UVX OC values by 3% and 5% at 1 and 2 months. The SHG signal was higher in CXL corneas than untreated corneas, both at 1 and 2 months after surgery, by 18% and 26% and 1% and 10% for RGX and UVX, respectively. Conclusions Increased OC corresponded with increased collagen fiber organization in CXL corneas. Changes in collagen organization parallel reported temporal changes in cornea stiffness after CXL and also, surprisingly, are detected deeper in the stroma than the regions stiffened by collagen cross-links.
Collapse
|
12
|
Sun X, Yang X, Song W, Ren L. Construction and Evaluation of Collagen-Based Corneal Grafts Using Polycaprolactone To Improve Tension Stress. ACS OMEGA 2020; 5:674-682. [PMID: 31956817 PMCID: PMC6964271 DOI: 10.1021/acsomega.9b03297] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2019] [Accepted: 12/18/2019] [Indexed: 05/09/2023]
Abstract
The emergence of innovative surgical procedures using partial thickness corneal transplant has created a need for the development of corneal grafts to replace pathologic corneal tissue. Corneal repair materials have been successfully prepared in the past 10 years, but they were difficult to be used in clinics because of the unbearable tension caused by interrupted suture during routine surgery. However, polycaprolactone (PCL), a medical polymer material, can solve this problem. Therefore, a hierarchical collagen (Col)-based corneal graft with curvature, consisting of a transparent core part composed of collagen in the center and a mechanically robust fixed part containing collagen and polycaprolactone in the edge, was used as a potential corneal graft for corneal repair and regeneration in this study. The hierarchical collagen-based corneal grafts [collagen-polycaprolactone (Col-PCL) membranes] that are capable of mimicking the native cornea were developed based on chemical and thermal crosslinking mechanisms. The water adsorption of Col-PCL membranes could reach over 80% similar to that of human cornea, and its swelling could reach over 400%. More importantly, the formed Col-PCL membranes could resist a larger tensile strength (1.1 ± 0.03 MPa) before rupturing in comparison with pure collagen membranes and polycaprolactone membranes. Furthermore, the biodegradable Col-PCL membranes could facilitate cell adhesion and proliferation as well as cell migration (exhibiting epithelial wound coverage in <5 days), which showed promise as corneal grafts for cornea tissue engineering.
Collapse
Affiliation(s)
- Xiaomin Sun
- School
of Materials Science and Engineering, Key Laboratory of Biomedical Engineering
of Guangdong Province, Key Laboratory of Biomedical Materials and Engineering
of the Ministry of Education, and Innovation Center for Tissue Restoration and
Reconstruction, South China University of
Technology, Guangzhou 510006, P. R. China
- National
Engineering Research Center for Tissue Restoration and Reconstruction, Guangzhou 510006, P. R. China
| | - Xiangjing Yang
- School
of Materials Science and Engineering, Key Laboratory of Biomedical Engineering
of Guangdong Province, Key Laboratory of Biomedical Materials and Engineering
of the Ministry of Education, and Innovation Center for Tissue Restoration and
Reconstruction, South China University of
Technology, Guangzhou 510006, P. R. China
- National
Engineering Research Center for Tissue Restoration and Reconstruction, Guangzhou 510006, P. R. China
| | - Wenjing Song
- School
of Materials Science and Engineering, Key Laboratory of Biomedical Engineering
of Guangdong Province, Key Laboratory of Biomedical Materials and Engineering
of the Ministry of Education, and Innovation Center for Tissue Restoration and
Reconstruction, South China University of
Technology, Guangzhou 510006, P. R. China
- National
Engineering Research Center for Tissue Restoration and Reconstruction, Guangzhou 510006, P. R. China
| | - Li Ren
- School
of Materials Science and Engineering, Key Laboratory of Biomedical Engineering
of Guangdong Province, Key Laboratory of Biomedical Materials and Engineering
of the Ministry of Education, and Innovation Center for Tissue Restoration and
Reconstruction, South China University of
Technology, Guangzhou 510006, P. R. China
- National
Engineering Research Center for Tissue Restoration and Reconstruction, Guangzhou 510006, P. R. China
- Sino-Singapore
International Joint Research Institute, Guangzhou 510555, P. R. China
- Guangzhou
Regenerative Medicine and Health Guangdong Laboratory, Guangzhou 510005, P. R. China
| |
Collapse
|
13
|
Lee SL, Chen YF, Dong CY. Second harmonic generation imaging reveals asymmetry in the rotational helicity of collagen lamellae in chicken corneas. BIOMEDICAL OPTICS EXPRESS 2019; 10:5223-5234. [PMID: 31646043 PMCID: PMC6788602 DOI: 10.1364/boe.10.005223] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 09/04/2019] [Accepted: 09/05/2019] [Indexed: 05/03/2023]
Abstract
High tensile strength and optical clarity are unique properties of the cornea. These features are dictated by the three-dimensional architecture of corneal lamellae. Therefore, understanding the microscopic details of the cornea's structural organization may contribute to the development of artificial cornea for the treatment of corneal diseases. In this study, the combination of forward second harmonic generation (SHG) microcopy and fast Fourier-transform based image analysis was used to characterize the depth-dependent superstructure of chicken corneal stroma. Our results show that from the surface, adjacent lamellae of anterior chicken cornea lamella rotate in a counterclockwise direction, and the same rotational helicity is observed in left and right corneas. Furthermore, the overall average rotational pitch of lamellae is 0.92 ± 0.11 degree/µm which persists for 176 ± 14 µm in the anterior stroma. As depth further increased, the rate of lamellar rotation decreases. Upon reaching posterior stroma, lamellar orientation remains constant. Throughout the stroma, collagen lamellae in chicken rotate a total of 169 ± 21 degrees. The lack of lamellar rotation in posterior stroma suggests that packing efficiency cannot be used to explain the helicity of depth-dependent rotation of anterior stroma. In addition, although the right cornea has a higher rotational pitch (0.95 ± 11 vs 0.90 ± 10 degrees/µm) and thinner anterior stroma (173 ± 13 vs 179 ± 14 µm) than the left cornea, the two effects cancel each other out and result in similar total angular rotation of anterior stroma (161 ± 23 and 165 degrees ± 21). Finally, our observation of a total angular rotation of 169 ± 21 degrees shows that within experimental error, chicken cornea lamellae rotate around 180 degrees or half of a complete turn. Additional studies are needed to arrive at an explanation of chicken superstructure in three dimensions.
Collapse
Affiliation(s)
- Sheng-Lin Lee
- Department of Physics, National Taiwan University, Taipei 106, Taiwan, China
| | - Yang-Fang Chen
- Department of Physics, National Taiwan University, Taipei 106, Taiwan, China
| | - Chen-Yuan Dong
- Department of Physics, National Taiwan University, Taipei 106, Taiwan, China
| |
Collapse
|
14
|
Abstract
Two-photon (2P) microscopy is a powerful tool for imaging and exploring label-free biological tissues at high resolution. Although this type of microscopy has been demonstrated in ex vivo ocular tissues of both humans and animal models, imaging the human eye in vivo has always been challenging. This work presents a novel compact 2P microscope for non-contact imaging of the anterior part of the living human eye. The performance of the instrument was tested and the maximum permissible exposure to protect ocular tissues established. To the best of our knowledge, 2P images of the in vivo human cornea, the sclera and the trabecular meshwork are shown for the very first time. Acquired images are of enough quality to visualize collagen arrangement and morphological features of clinical interest. Future implementations of this technique may constitute a potential tool for early diagnosis of ocular diseases at submicron scale.
Collapse
|
15
|
Ávila FJ, Artal P, Bueno JM. Quantitative Discrimination of Healthy and Diseased Corneas With Second Harmonic Generation Microscopy. Transl Vis Sci Technol 2019; 8:51. [PMID: 31293806 PMCID: PMC6601709 DOI: 10.1167/tvst.8.3.51] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Accepted: 04/30/2019] [Indexed: 12/20/2022] Open
Abstract
Purpose To analyze the spatial organization of pathological corneas with second harmonic generation (SHG) imaging and to provide a proof of concept to objectively distinguish these from the healthy corneas. Methods A custom-built SHG microscope was used to image the anterior stroma of ex vivo corneas, both control and affected by some representative pathologies. The structure tensor (ST) was employed as a metric to explore and quantify the alterations in the spatial distribution of the collagen lamellae. Results The collagen arrangement differed between healthy and pathological samples. The former showed a regular distribution and a low structural dispersion (SD < 40°) within the stroma with a well-defined dominant orientation. This regular arrangement drastically turns into a disorganized pattern in pathological corneas (SD > 40°). Conclusions The combination of SHG imaging and the ST allows obtaining quantitative information to differentiate the stromal collagen organization in healthy and diseased corneas. This approach represents a feasible and powerful technique with potential applications in clinical corneal diagnoses. Translational Relevance The ST applied to SHG microscopy images of the corneal stroma provides an experimental objective score to differentiate control from pathological or damaged corneas. Future implementations of this technique in clinical environments might might be a promising tool in Ophthalmology, not only to diagnose and monitor corneal diseases, but also to follow-up surgical outcome.
Collapse
Affiliation(s)
- Francisco J Ávila
- Laboratorio de Óptica, Instituto Universitario de Investigación en Óptica y Nanofísica, Universidad de Murcia, Murcia, Spain
| | - Pablo Artal
- Laboratorio de Óptica, Instituto Universitario de Investigación en Óptica y Nanofísica, Universidad de Murcia, Murcia, Spain
| | - Juan M Bueno
- Laboratorio de Óptica, Instituto Universitario de Investigación en Óptica y Nanofísica, Universidad de Murcia, Murcia, Spain
| |
Collapse
|
16
|
Nath S, Shen C, Koziarz A, Banfield L. Protocol for a systematic review, meta-analysis, and trial sequential analysis of clinical outcomes following accelerated versus conventional corneal collagen cross-linking for corneal ectasia. Syst Rev 2019; 8:85. [PMID: 30947752 PMCID: PMC6449983 DOI: 10.1186/s13643-019-1004-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 03/25/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Collagen cross-linking (CXL) is an evolving procedure that enhances the biomechanical rigidity of the cornea and can slow or halt ectatic disease. CXL requires delivery of 5.4 J/cm2 of ultraviolet A (UVA) radiation to a cornea saturated with riboflavin in order to induce cross-link formation. The conventional CXL procedure achieves this fluence by exposing the cornea to a 3 mW/cm2 UVA lamp for 30 min; however, some surgeons have proposed accelerated protocols which achieve the same fluence in a shorter period of time by using a higher power light source. Whether accelerated protocols are as effective in arresting ectasia as the established conventional procedure remains unclear. Accordingly, this study will systematically review and synthesise the evidence on accelerated CXL and compare it to the conventional approach across an array of clinical outcomes. METHODS We will search 16 electronic databases, including MEDLINE, Embase, and the Cochrane Library, from inception to February 1, 2019. We will include all randomised controlled trials comparing accelerated and conventional CXL for any corneal ectatic disease. Two reviewers will independently screen search results to identify eligible articles, complete data collection, and conduct quality assessment. The quality of individual trials will be assessed using the Cochrane Collaboration's Risk of Bias Assessment Tool. Our primary outcome will be the change in maximal keratometry (Kmax) at 12 months following treatment. Additional outcomes will include: incidence of disease progression, incidence of serious adverse events, as well as change in Kmax at longest follow-up, mean stromal demarcation line depth, mean uncorrected distance visual acuity, mean corrected distance visual acuity, mean Kmax, mean endothelial cell density, mean central corneal thickness, mean spherical equivalent, mean intraocular pressure, and mean corneal power, at 12 months following treatment. We will calculate relative risks and 95% confidence intervals (CIs) for dichotomous outcomes and weighted mean differences and corresponding 95% CIs for continuous outcomes. Prespecified subgroup analyses will be performed to investigate heterogeneity. We will rate the overall quality of evidence using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. DISCUSSION This review will provide a comprehensive evaluation of the evidence on accelerated and conventional CXL approaches and serve to inform clinical practice, medical device design, and future research. Evaluating variations of the CXL protocol aimed at reducing treatment duration is of critical importance and a prerequisite to expanding treatment availability to more patients. SYSTEMATIC REVIEW REGISTRATION PROSPERO CRD42018104151.
Collapse
Affiliation(s)
- Siddharth Nath
- Division of Ophthalmology, Department of Surgery, McMaster University, Hamilton, Ontario Canada
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote School of Medicine, Faculty of Health Sciences, McMaster University, 1200 Main Street West, Room 4N53, Hamilton, Ontario L8N 3Z5 Canada
| | - Carl Shen
- Division of Ophthalmology, Department of Surgery, McMaster University, Hamilton, Ontario Canada
| | - Alex Koziarz
- Faculty of Medicine, University of Toronto, Toronto, Ontario Canada
| | - Laura Banfield
- Health Sciences Library, McMaster University, Hamilton, Ontario Canada
| |
Collapse
|