1
|
Dilley KK, Prasad KR, Nguyen TV, Stokolosa A, Borden PA, Heur JM, Kim S, Hill MG, Wong BJF. Second harmonic generation microscopy of electromechanical reshaping on corneal collagen. Exp Eye Res 2024; 244:109941. [PMID: 38782177 DOI: 10.1016/j.exer.2024.109941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Revised: 05/16/2024] [Accepted: 05/21/2024] [Indexed: 05/25/2024]
Abstract
Refractive errors remain a global health concern, as a large proportion of the world's population is myopic. Current ablative approaches are costly, not without risks, and not all patients are candidates for these procedures. Electromechanical reshaping (EMR) has been explored as a viable cost-effective modality to directly shape tissues, including cartilage. In this study, stromal collagen structure and fibril orientation was examined before and after EMR with second-harmonic generation microscopy (SHG), a nonlinear multiphoton imaging method that has previously been used to study native corneal collagen with high spatial resolution. EMR, using a milled metal contact lens and potentiostat, was performed on the corneas of five extracted rabbit globes. SHG was performed using a confocal microscopy system and all images underwent collagen fibril orientation analysis. The collagen SHG signal in controls is uniform and is similarly seen in samples treated with pulsed potential, while continuous EMR specimens have reduced, nonhomogeneous signal. Collagen fibril orientation in native tissue demonstrates a broad distribution with suggestion of another peak evolving, while with EMR treated eyes a bimodal characteristic becomes readily evident. Pulsed EMR may be a means to correct refractive errors, as when comparing its SHG signal to negative control, preservation of collagen structures with little to no damage is observed. From collagen fiber orientation analysis, it can be inferred that simple DC application alters the structure of collagen. Future studies will involve histological assessment of these layers and multi-modal imaging analysis of dosimetry.
Collapse
Affiliation(s)
- Katelyn K Dilley
- Beckman Laser Institute & Medical Clinic, University of California - Irvine, CA, 92612, USA
| | - Karthik R Prasad
- Beckman Laser Institute & Medical Clinic, University of California - Irvine, CA, 92612, USA; School of Medicine, University of California - Irvine, Irvine, CA, 92617, USA
| | - Theodore V Nguyen
- Beckman Laser Institute & Medical Clinic, University of California - Irvine, CA, 92612, USA; School of Medicine, University of California - Irvine, Irvine, CA, 92617, USA
| | - Anna Stokolosa
- Department of Biomedical Engineering, University of California - Irvine, Irvine, CA, 92697, USA
| | - Pamela A Borden
- Beckman Laser Institute & Medical Clinic, University of California - Irvine, CA, 92612, USA; Department of Biomedical Engineering, University of California - Irvine, Irvine, CA, 92697, USA
| | - J Martin Heur
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, 90033, USA
| | - Sehwan Kim
- Department of Biomedical Engineering, Beckman Laser Institute Korea, Dankook University, Cheonan, 31116, Republic of Korea
| | - Michael G Hill
- Department of Chemistry, Occidental College, Los Angeles, CA, 90041, USA
| | - Brian J F Wong
- Beckman Laser Institute & Medical Clinic, University of California - Irvine, CA, 92612, USA; School of Medicine, University of California - Irvine, Irvine, CA, 92617, USA; Department of Biomedical Engineering, University of California - Irvine, Irvine, CA, 92697, USA; Department of Otolaryngology - Head and Neck Surgery, University of California - Irvine, School of Medicine, Orange, CA, 92868, USA.
| |
Collapse
|
2
|
Liang Z, Zhang Z, Lu P, Yang J, Han L, Liu S, Zhou T, Li J, Zhang J. The effect of charges on the corneal penetration of solid lipid nanoparticles loaded econazole after topical administration in rabbits. Eur J Pharm Sci 2023:106494. [PMID: 37315870 DOI: 10.1016/j.ejps.2023.106494] [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: 01/17/2023] [Revised: 05/09/2023] [Accepted: 06/11/2023] [Indexed: 06/16/2023]
Abstract
Fungal keratitis is an infectious disease caused by pathogenic fungi with a high blindness rate. Econazole (ECZ) is an imidazole antifungal drug with insoluble ability. Econazole-loaded solid lipid nanoparticles (E-SLNs) were prepared by microemulsion method, then modified with positive and negative charge. The mean diameter of cationic E-SLNs, nearly neutral E-SLNs and anionic E-SLNs were 18.73±0.14, 19.05±0.28, 18.54±0.10 nm respectively. The Zeta potential of these different charged SLNs formulations were 19.13±0.89, -2.20±0.10, -27.40±0.67 mV respectively. The Polydispersity Index (PDI) of these three kinds of nanoparticles were about 0.2. The Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC) analysis showed that the nanoparticles were a homogeneous system. Compared with Econazole suspension (E-Susp), SLNs exhibited sustained release capability, stronger corneal penetration and enhanced inhibition of pathogenic fungi without irritation. The antifungal ability was further improved after cationic charge modification compared with E-SLNs. Studies on pharmacokinetics showed that the order of the AUC and t1/2 of different preparations was cationic E-SLNs > nearly neutral E-SLNs > anionic E-SLNs > E-Susp in cornea and aqueous humor. It was shown that SLNs could increase corneal penetrability and ocular bioavailability while these capabilities were further enhanced with positive charge modification compared with negative charge ones.
Collapse
Affiliation(s)
- Zhen Liang
- Henan Eye Hospital, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, Zhengzhou 450003, China
| | - Zhen Zhang
- Henan Eye Hospital, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, Zhengzhou 450003, China
| | - Ping Lu
- Henan Eye Hospital, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, Zhengzhou 450003, China
| | - Jingjing Yang
- Henan Eye Hospital, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, Zhengzhou 450003, China
| | - Lei Han
- Henan Eye Hospital, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, Zhengzhou 450003, China
| | - Susu Liu
- Henan Eye Hospital, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, Zhengzhou 450003, China
| | - Tianyang Zhou
- Henan Eye Hospital, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, Zhengzhou 450003, China
| | - Jingguo Li
- Henan Eye Hospital, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, Zhengzhou 450003, China
| | - Junjie Zhang
- Henan Eye Hospital, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, Zhengzhou 450003, China.
| |
Collapse
|
3
|
Santana CP, Matter BA, Patil MA, Silva-Cunha A, Kompella UB. Corneal Permeability and Uptake of Twenty-Five Drugs: Species Comparison and Quantitative Structure-Permeability Relationships. Pharmaceutics 2023; 15:1646. [PMID: 37376094 DOI: 10.3390/pharmaceutics15061646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2023] [Revised: 05/28/2023] [Accepted: 05/29/2023] [Indexed: 06/29/2023] Open
Abstract
The purpose of this study was to determine corneal permeability and uptake in rabbit, porcine, and bovine corneas for twenty-five drugs using an N-in-1 (cassette) approach and relate these parameters to drug physicochemical properties and tissue thickness through quantitative structure permeability relationships (QSPRs). A twenty-five-drug cassette containing β-blockers, NSAIDs, and corticosteroids in solution at a micro-dose was exposed to the epithelial side of rabbit, porcine, or bovine corneas mounted in a diffusion chamber, and the corneal drug permeability and tissue uptake were monitored using an LC-MS/MS method. Data obtained were used to construct and evaluate over 46,000 quantitative structure-permeability (QSPR) models using multiple linear regression, and the best-fit models were cross-validated by Y-randomization. Drug permeability was generally higher in rabbit cornea and comparable between bovine and porcine corneas. Permeability differences between species could be explained in part by differences in corneal thickness. Corneal uptake between species correlated with a slope close to 1, indicating generally similar drug uptake per unit weight of tissue. A high correlation was observed between bovine, porcine, and rabbit corneas for permeability and between bovine and porcine corneas for uptake (R2 ≥ 0.94). MLR models indicated that drug characteristics such as lipophilicity (LogD), heteroatom ratio (HR), nitrogen ratio (NR), hydrogen bond acceptors (HBA), rotatable bonds (RB), index of refraction (IR), and tissue thickness (TT) are of great influence on drug permeability and uptake. When data for all species along with thickness as a parameter was used in MLR, the best fit equation for permeability was Log (% transport/cm2·s) = 0.441 LogD - 8.29 IR + 8.357 NR - 0.279 HBA - 3.833 TT + 10.432 (R2 = 0.826), and the best-fit equation for uptake was Log (%/g) = 0.387 LogD + 4.442 HR + 0.105 RB - 0.303 HBA - 2.235 TT + 1.422 (R2 = 0.750). Thus, it is feasible to explain corneal drug delivery in three species using a single equation.
Collapse
Affiliation(s)
- Cleildo P Santana
- Department of Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
- Faculty of Pharmacy, Federal University of Minas Gerais, Belo Horizonte 31270-901, MG, Brazil
| | - Brock A Matter
- Department of Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Madhoosudan A Patil
- Department of Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Armando Silva-Cunha
- Faculty of Pharmacy, Federal University of Minas Gerais, Belo Horizonte 31270-901, MG, Brazil
| | - Uday B Kompella
- Department of Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
- Department of Ophthalmology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
- Department of Bioengineering, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
- Colorado Center for Nanomedicine and Nanosafety, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| |
Collapse
|
4
|
Martínez-Ojeda RM, Mugnier LM, Artal P, Bueno JM. Blind deconvolution of second harmonic microscopy images of the living human eye. BIOMEDICAL OPTICS EXPRESS 2023; 14:2117-2128. [PMID: 37206134 PMCID: PMC10191662 DOI: 10.1364/boe.486989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Revised: 03/17/2023] [Accepted: 03/19/2023] [Indexed: 05/21/2023]
Abstract
Second harmonic generation (SHG) imaging microscopy of thick biological tissues is affected by the presence of aberrations and scattering within the sample. Moreover, additional problems, such as uncontrolled movements, appear when imaging in-vivo. Deconvolution methods can be used to overcome these limitations under some conditions. In particular, we present here a technique based on a marginal blind deconvolution approach for improving SHG images obtained in vivo in the human eye (cornea and sclera). Different image quality metrics are used to quantify the attained improvement. Collagen fibers in both cornea and sclera are better visualized and their spatial distributions accurately assessed. This might be a useful tool to better discriminate between healthy and pathological tissues, especially those where changes in collagen distribution occur.
Collapse
Affiliation(s)
- Rosa M. Martínez-Ojeda
- Laboratorio de Óptica,
Instituto Universitario de Investigación en
Óptica y Nanofísica, Universidad de
Murcia, Campus de Espinardo (Ed. 34), 30100 Murcia, Spain
| | | | - Pablo Artal
- Laboratorio de Óptica,
Instituto Universitario de Investigación en
Óptica y Nanofísica, Universidad de
Murcia, Campus de Espinardo (Ed. 34), 30100 Murcia, Spain
| | - 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
| |
Collapse
|
5
|
Lan G, Twa MD, Song C, Feng J, Huang Y, Xu J, Qin J, An L, Wei X. In vivo corneal elastography: A topical review of challenges and opportunities. Comput Struct Biotechnol J 2023; 21:2664-2687. [PMID: 37181662 PMCID: PMC10173410 DOI: 10.1016/j.csbj.2023.04.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 04/07/2023] [Accepted: 04/12/2023] [Indexed: 05/16/2023] Open
Abstract
Clinical measurement of corneal biomechanics can aid in the early diagnosis, progression tracking, and treatment evaluation of ocular diseases. Over the past two decades, interdisciplinary collaborations between investigators in optical engineering, analytical biomechanical modeling, and clinical research has expanded our knowledge of corneal biomechanics. These advances have led to innovations in testing methods (ex vivo, and recently, in vivo) across multiple spatial and strain scales. However, in vivo measurement of corneal biomechanics remains a long-standing challenge and is currently an active area of research. Here, we review the existing and emerging approaches for in vivo corneal biomechanics evaluation, which include corneal applanation methods, such as ocular response analyzer (ORA) and corneal visualization Scheimpflug technology (Corvis ST), Brillouin microscopy, and elastography methods, and the emerging field of optical coherence elastography (OCE). We describe the fundamental concepts, analytical methods, and current clinical status for each of these methods. Finally, we discuss open questions for the current state of in vivo biomechanics assessment techniques and requirements for wider use that will further broaden our understanding of corneal biomechanics for the detection and management of ocular diseases, and improve the safety and efficacy of future clinical practice.
Collapse
Affiliation(s)
- Gongpu Lan
- Guangdong-Hong Kong-Macao Intelligent Micro-Nano Optoelectronic Technology Joint Laboratory, School of Physics and Optoelectronic Engineering, Foshan University, Foshan, Guangdong 528000, China
- Weiren Meditech Co., Ltd., Foshan, Guangdong 528000, China
| | - Michael D Twa
- College of Optometry, University of Houston, Houston, TX 77204, United States
| | - Chengjin Song
- Guangdong-Hong Kong-Macao Intelligent Micro-Nano Optoelectronic Technology Joint Laboratory, School of Physics and Optoelectronic Engineering, Foshan University, Foshan, Guangdong 528000, China
| | - JinPing Feng
- Institute of Engineering and Technology, Hubei University of Science and Technology, Xianning, Hubei 437100, China
| | - Yanping Huang
- Guangdong-Hong Kong-Macao Intelligent Micro-Nano Optoelectronic Technology Joint Laboratory, School of Physics and Optoelectronic Engineering, Foshan University, Foshan, Guangdong 528000, China
- Weiren Meditech Co., Ltd., Foshan, Guangdong 528000, China
| | - Jingjiang Xu
- Guangdong-Hong Kong-Macao Intelligent Micro-Nano Optoelectronic Technology Joint Laboratory, School of Physics and Optoelectronic Engineering, Foshan University, Foshan, Guangdong 528000, China
- Weiren Meditech Co., Ltd., Foshan, Guangdong 528000, China
| | - Jia Qin
- Weiren Meditech Co., Ltd., Foshan, Guangdong 528000, China
| | - Lin An
- Weiren Meditech Co., Ltd., Foshan, Guangdong 528000, China
| | - Xunbin Wei
- Biomedical Engineering Department, Peking University, Beijing 100081, China
- International Cancer Institute, Peking University, Beijing 100191, China
- Institute of Medical Technology, Peking University Health Science Center, Beijing 100191, China
| |
Collapse
|
6
|
Carmichael-Martins A, Gast TJ, Burns SA, Walker BR, King BJ. Characterization of the human iridocorneal angle in vivo using a custom design goniolens with OCT gonioscopy. BIOMEDICAL OPTICS EXPRESS 2022; 13:4652-4667. [PMID: 36187241 PMCID: PMC9484429 DOI: 10.1364/boe.465317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Revised: 07/18/2022] [Accepted: 07/27/2022] [Indexed: 06/16/2023]
Abstract
Intraocular pressure (IOP) is the only modifiable risk factor for glaucoma progression, and many treatments target the trabecular meshwork (TM). Imaging this region in vivo is challenging due to optical limitations of imaging through the cornea at high angles. We propose a gonioscopic OCT approach using a custom goniolens and a commercially available OCT device to improve imaging of the TM, Schlemm's canal (SC) and adjacent structures within the iridocorneal angle (ICA). The goniolens is modified with a plano-convex focusing lens and placed on the eye optically mated with goniogel and aided by a 3D adjustable mount. Gonioscopic OCT volume scans are acquired to image SC. Transverse enface images allowed measurements of SC over a 45° section of the ICA for the first time and revealed locations of SC narrowing. The band of extracanalicular limbal lamina and corneoscleral bands were imaged in most subjects and these bands were confirmed using exterior OCT imaging. The polarization dependence of the visibility of these structures is studied by polarization rotation the OCT beam with a half-wave plate, allowing increased contrast of SC. Gonioscopic OCT has successfully been used to image the human ICA in 3D in vivo. This approach provides more detailed characterization of the TM and SC, enhancing their contrast against their birefringent backgrounds.
Collapse
Affiliation(s)
| | - Thomas J. Gast
- School of Optometry, Indiana University, Bloomington, Indiana 47401, USA
| | - Stephen A. Burns
- School of Optometry, Indiana University, Bloomington, Indiana 47401, USA
| | - Brittany R. Walker
- School of Optometry, Indiana University, Bloomington, Indiana 47401, USA
| | - Brett J. King
- School of Optometry, Indiana University, Bloomington, Indiana 47401, USA
| |
Collapse
|
7
|
Gubarkova EV, Elagin VV, Dudenkova VV, Kuznetsov SS, Karabut MM, Potapov AL, Vorontsov DA, Vorontsov AY, Sirotkina MA, Zagaynova EV, Gladkova ND. Multiphoton tomography in differentiation of morphological and molecular subtypes of breast cancer: A quantitative analysis. JOURNAL OF BIOPHOTONICS 2021; 14:e202000471. [PMID: 33522719 DOI: 10.1002/jbio.202000471] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 01/26/2021] [Accepted: 01/28/2021] [Indexed: 06/12/2023]
Abstract
In this study multiphoton tomography, based on second harmonic generation (SHG), and two-photon-excited fluorescence (TPEF) was used to visualize both the extracellular matrix and tumor cells in different morphological and molecular subtypes of human breast cancer. It was shown, that quantified assessment of the SHG based imaging data has great potential to reveal differences of collagen quantity, organization and uniformity in both low- and highly- aggressive invasive breast cancers. The values of quantity and uniformity of the collagen fibers distribution were significantly higher in low-aggressive breast cancer compared to the highly-aggressive subtypes, while the value representing collagen organization was lower in the former type. Additionally, it was shown, that TPEF detection of elastin fibers and amyloid protein may be used as a biomarker of detection the low-aggressive breast cancer subtype. Thus, TPEF/SHG imaging offers the possibility of becoming a useful tool for the rapid diagnosis of various subtypes of breast cancer during biopsy as well as for the intraoperative determinination of tumor-positive resection margins.
Collapse
Affiliation(s)
| | - Vadim V Elagin
- Privolzhsky Research Medical University, Nizhny Novgorod, Russia
| | | | | | - Maria M Karabut
- Privolzhsky Research Medical University, Nizhny Novgorod, Russia
| | - Arseny L Potapov
- Privolzhsky Research Medical University, Nizhny Novgorod, Russia
| | | | | | | | - Elena V Zagaynova
- Privolzhsky Research Medical University, Nizhny Novgorod, Russia
- Lobachevsky State University of Nizhni Novgorod, Nizhny Novgorod, Russia
| | | |
Collapse
|
8
|
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
|
9
|
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
|
10
|
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
|
11
|
Lee SL, He MY, Chen YF, Dong CY. Quantification of collagen structural changes during chick corneal development. JOURNAL OF BIOPHOTONICS 2020; 13:e201900144. [PMID: 31465146 DOI: 10.1002/jbio.201900144] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 08/27/2019] [Accepted: 08/28/2019] [Indexed: 06/10/2023]
Abstract
As the most abundant structural mammalian protein, collagen has been implicated in the pathogenesis of numerous diseases such as osteogenesis imperfecta, and cancer. In the case of cornea, abnormal cornea development can lead to conditions such as agenesis, megalocornea, microcornea, and cornea plana. Therefore, understanding the mechanisms of collagen assembly during development may contribute to the prevention or treatment of corneal diseases. In this study, we applied fast Fourier transform second harmonic generation microscopy to quantify parameters of corneal structures during chick development. Our results show that both the rotational pitch and overall rotational angle of corneal stroma modulate between E9 and E19. In addition, we found that corneal structures between left and right corneas are highly correlated during development.
Collapse
Affiliation(s)
- Sheng-Lin Lee
- Department of Physics, National Taiwan University, Taipei, Taiwan, ROC
| | - Ming-Ye He
- Department of Physics, National Taiwan University, Taipei, Taiwan, ROC
| | - Yang-Fang Chen
- Department of Physics, National Taiwan University, Taipei, Taiwan, ROC
| | - Chen-Yuan Dong
- Department of Physics, National Taiwan University, Taipei, Taiwan, ROC
| |
Collapse
|
12
|
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
|
13
|
Liu J, Li Z, Li J, Liu Z. Application of benzonase in preparation of decellularized lamellar porcine corneal stroma for lamellar keratoplasty. J Biomed Mater Res A 2019; 107:2547-2555. [PMID: 31330094 PMCID: PMC6771539 DOI: 10.1002/jbm.a.36760] [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: 10/16/2018] [Revised: 07/09/2019] [Accepted: 07/12/2019] [Indexed: 11/10/2022]
Abstract
This study was to develop anovel and efficient method using endonuclease (benzonase) to preparedecellularized lamellar porcine corneal stroma (DLPCS). The DLPCS was preparedfrom native lamellar porcine corneal stroma (NLPCS) and was treated with 1000 U/ml benzonase for 5hours. We conducted the following measurements and animal transplantation tocompare DLPCS and NLPCS. The residual DNA was decreased significantly from 367.13 ± 19.96 ng/mg to 15.41 ± 0.65 ng/mg after treatment of benzonase by the detection of fluorescentnucleic acid stain. The residual benzonase was also less than detection limit.There was no significant difference in light transmittance of DLPCS comparedwith NLPCS. The extracts of DLPCS did not inhibit cell proliferation of human cornealepithelial cells, mouse fibroblast (L‐929) and African green monkey kidney cell(Vero cell). The DLPCS was transplanted into the corneas of rabbit by lamellarkeratoplasty. There was no corneal melting and graft rejection been observedwithin 12 months. The images demonstrated that the repairment of corneal nervesand keratocytes of DLPCS were in indentical shape and reflection compared withnormal cornea, and no obvious inflammatory cells were observed postoperation, byin vivo confocal microscopy. We provided novel evidence that the application ofbenzonase may improve the quality of DLPCS.
Collapse
Affiliation(s)
- Jing Liu
- Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Eye Institute of Xiamen University; College of Medicine, Xiamen University, Xiamen, Fujian Province, China
| | - Zhihan Li
- Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Eye Institute of Xiamen University; College of Medicine, Xiamen University, Xiamen, Fujian Province, China
| | - Jie Li
- Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Eye Institute of Xiamen University; College of Medicine, Xiamen University, Xiamen, Fujian Province, China
| | - Zuguo Liu
- Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Eye Institute of Xiamen University; College of Medicine, Xiamen University, Xiamen, Fujian Province, China.,Xiang'an Hospital of Xiamen University.,Xiamen Eye Center of Xiamen University
| |
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
|
Bueno JM, Ávila FJ, Artal P. Comparing the performance of a femto fiber-based laser and a Ti:sapphire used for multiphoton microscopy applications. APPLIED OPTICS 2019; 58:3830-3835. [PMID: 31158196 DOI: 10.1364/ao.58.003830] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 04/16/2019] [Indexed: 06/09/2023]
Abstract
Ti:sapphire laser systems are the more extended excitation sources in multiphoton (MP) microscopy. Although tunable, the cost, size, and lack of portability often limit their use in some research fields. Femtosecond fiber-based lasers represent an attractive alternative since they are portable, compact, and affordable. Most MP applications using these devices employ wavelengths beyond 1000 nm. This work evaluates the performance of a mode-locked fiber-based laser emitting at 780 nm (within the spectral region often used with Ti:sapphire devices) for use in MP imaging microscopy. MP images acquired with this laser system have been compared with those obtained with a "regular" solid-state source. Results herein show that the images recorded with both laser sources were similar, independently of the depth location of the imaged plane. The structural information contained in the images hardly differed. Moreover, the images of deeper layers improved by means of adaptive optics were also similar. These ultrafast laser sources are expected to enhance the impact of MP microscopy in basic research, as well as in biomedical environments.
Collapse
|
17
|
Finding an Optimal Corneal Xenograft Using Comparative Analysis of Corneal Matrix Proteins Across Species. Sci Rep 2019; 9:1876. [PMID: 30755666 PMCID: PMC6372616 DOI: 10.1038/s41598-018-38342-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 12/19/2018] [Indexed: 11/08/2022] Open
Abstract
Numerous animal species have been proposed as sources of corneal tissue for obtaining decellularized xenografts. The selection of an appropriate animal model must take into consideration the differences in the composition and structure of corneal proteins between humans and other animal species in order to minimize immune response and improve outcome of the xenotransplant. Here, we compared the amino-acid sequences of 16 proteins present in the corneal stromal matrix of 14 different animal species using Basic Local Alignment Search Tool, and calculated a similarity score compared to the respective human sequence. Primary amino acid structures, isoelectric point and grand average of hydropathy (GRAVY) values of the 7 most abundant proteins (i.e. collagen α-1 (I), α-1 (VI), α-2 (I) and α-3 (VI), as well as decorin, lumican, and keratocan) were also extracted and compared to those of human. The pig had the highest similarity score (91.8%). All species showed a lower proline content compared to human. Isoelectric point of pig (7.1) was the closest to the human. Most species have higher GRAVY values compared to human except horse. Our results suggest that porcine cornea has a higher relative suitability for corneal transplantation into humans compared to other studied species.
Collapse
|
18
|
Quantitative Analysis of the Corneal Collagen Distribution after In Vivo Cross-Linking with Second Harmonic Microscopy. BIOMED RESEARCH INTERNATIONAL 2019; 2019:3860498. [PMID: 30756083 PMCID: PMC6348900 DOI: 10.1155/2019/3860498] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 10/24/2018] [Accepted: 12/04/2018] [Indexed: 12/14/2022]
Abstract
Corneal cross-linking (CXL) is a surgical procedure able to modify corneal biomechanics and stabilize keratoconus progression. Although it is known that CXL produces changes in corneal collagen distribution, these are still a topic of discussion. Here we quantitatively compare the corneal stroma architecture between two animal models four weeks after in vivo conventional CXL treatment, with second harmonic generation (SHG) imaging microscopy and the structure tensor (ST). The healing stage and the stroma recovery were also analyzed by means of histological sections. Results show that the CXL effects depend on the initial arrangement of the corneal collagen. While the treatment increases the order in corneas with a low level of initial organization, corneas presenting a fairly regular pattern are hardly affected. Histological samples showed active keratocytes in anterior and middle stroma, what means that the recovery is still in progress. The combination of SHG imaging and the ST is able to objectively discriminate the changes suffered by the collagen arrangement after the CXL treatment, whose effectiveness depends on the initial organization of the collagen fibers within the corneal stroma.
Collapse
|
19
|
Ma J, Wang Y, Wei P, Jhanji V. Biomechanics and structure of the cornea: implications and association with corneal disorders. Surv Ophthalmol 2018; 63:851-861. [PMID: 29857022 DOI: 10.1016/j.survophthal.2018.05.004] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 05/17/2018] [Accepted: 05/21/2018] [Indexed: 12/14/2022]
Abstract
Recent studies have shown that alterations in corneal biomechanical properties are associated with corneal pathologies, particularly corneal ectasia. Moreover, these alterations may have implications with regard to the outcomes of therapeutic modalities and corneal refractive surgeries. We address corneal anatomy and its relevance to corneal biomechanical characteristics, as well as ocular and systemic conditions associated with changes in corneal biomechanics.
Collapse
Affiliation(s)
- Jiaonan Ma
- Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, China
| | - Yan Wang
- Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, China; Tianjin Eye Hospital, Tianjin Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Naikai University, Tianjin Medical University, Tianjin, China.
| | - Pinghui Wei
- Tianjin Eye Hospital, Tianjin Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Naikai University, Tianjin Medical University, Tianjin, China
| | - Vishal Jhanji
- UPMC Eye Center, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| |
Collapse
|
20
|
Germann JA, Martinez-Enriquez E, Marcos S. Quantization of collagen organization in the stroma with a new order coefficient. BIOMEDICAL OPTICS EXPRESS 2018; 9:173-189. [PMID: 29359095 PMCID: PMC5772573 DOI: 10.1364/boe.9.000173] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 11/20/2017] [Accepted: 11/21/2017] [Indexed: 05/20/2023]
Abstract
Many optical and biomechanical properties of the cornea, specifically the transparency of the stroma and its stiffness, can be traced to the degree of order and direction of the constituent collagen fibers. To measure the degree of order inside the cornea, a new metric, the order coefficient, was introduced to quantify the organization of the collagen fibers from images of the stroma produced with a custom-developed second harmonic generation microscope. The order coefficient method gave a quantitative assessment of the differences in stromal collagen arrangement across the cornea depths and between untreated stroma and cross-linked stroma.
Collapse
|
21
|
Bueno JM, Ávila FJ, Artal P. Comparison of second harmonic microscopy images of collagen-based ocular tissues with 800 and 1045 nm. BIOMEDICAL OPTICS EXPRESS 2017; 8:5065-5074. [PMID: 29188103 PMCID: PMC5695953 DOI: 10.1364/boe.8.005065] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 10/11/2017] [Accepted: 10/17/2017] [Indexed: 06/07/2023]
Abstract
Second harmonic generation (SHG) imaging is a well-suited multiphoton technique allowing visualization of biological tissues mainly composed of collagen with submicron resolution. Despite its inherent confocal properties, imaging of deeper layers within thick samples has still some limitations. Although the use of longer wavelengths might help to overcome this, the dependence between SHG signals and wavelength is still under discussion. We report here on the dependence with wavelength of SHG signals from collagen-based ocular tissues. The quality of SHG images for two commonly used excitation wavelengths (800 and 1045 nm) is studied. The analysis of the collagen structural information reveals that the information provided by both wavelengths is similar. It was also found that, independently of the depth location, 1045-nm SHG images presented always lower signal levels than those acquired with 800 nm. However, the contrast of the former images was higher, what may improve the visualization of certain features of interest.
Collapse
|
22
|
Marcos S, Werner JS, Burns SA, Merigan WH, Artal P, Atchison DA, Hampson KM, Legras R, Lundstrom L, Yoon G, Carroll J, Choi SS, Doble N, Dubis AM, Dubra A, Elsner A, Jonnal R, Miller DT, Paques M, Smithson HE, Young LK, Zhang Y, Campbell M, Hunter J, Metha A, Palczewska G, Schallek J, Sincich LC. Vision science and adaptive optics, the state of the field. Vision Res 2017; 132:3-33. [PMID: 28212982 PMCID: PMC5437977 DOI: 10.1016/j.visres.2017.01.006] [Citation(s) in RCA: 78] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Revised: 01/24/2017] [Accepted: 01/25/2017] [Indexed: 12/27/2022]
Abstract
Adaptive optics is a relatively new field, yet it is spreading rapidly and allows new questions to be asked about how the visual system is organized. The editors of this feature issue have posed a series of question to scientists involved in using adaptive optics in vision science. The questions are focused on three main areas. In the first we investigate the use of adaptive optics for psychophysical measurements of visual system function and for improving the optics of the eye. In the second, we look at the applications and impact of adaptive optics on retinal imaging and its promise for basic and applied research. In the third, we explore how adaptive optics is being used to improve our understanding of the neurophysiology of the visual system.
Collapse
Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | - Yuhua Zhang
- University of Alabama at Birmingham, Birmingham, USA
| | | | | | | | | | | | | |
Collapse
|
23
|
Ávila FJ, Del Barco O, Bueno JM. Polarization response of second-harmonic images for different collagen spatial distributions. JOURNAL OF BIOMEDICAL OPTICS 2016; 21:66015. [PMID: 27330006 DOI: 10.1117/1.jbo.21.6.066015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Accepted: 06/01/2016] [Indexed: 05/11/2023]
Abstract
The response to polarization of second-harmonic generation (SHG) microscopy images of samples with different collagen distributions (quasialigned, partially organized, and nonorganized) has been analyzed. A linear decay relationship between the external arrangement and polarization sensitivity was found. SHG signal from nonorganized samples presented a large structural dispersion and a weak dependence with incident polarization. Polarization dependence is also associated with the internal organization of the collagen fibers, directly related to the ratio of hyperpolarizabilities ρ. This parameter can experimentally be computed from the modulation of the SHG signal. The results show that both external and internal collagen structures are closely related. This provides a tool to obtain information of internal properties from the polarimetric response of the external spatial distribution of collagen, which might be useful in clinical diagnosis of pathologies related to changes in collagen structure.
Collapse
|
24
|
Ibares-Frías L, Gallego P, Cantalapiedra-Rodriguez R, Merayo-Lloves J, Martínez-García MC. Clinical, Refractive and Histological Reversibility of Corneal Additive Surgery in Deep Stroma in an Animal Model. Curr Eye Res 2016; 41:1192-201. [PMID: 26889567 DOI: 10.3109/02713683.2015.1114652] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE The aim was to evaluate the reversibility of the clinical and histological changes induced in the corneas of an animal model after removing an intracorneal ring segment (ICRS). METHODS Surgery for this study was performed in 38 eyes of an experimental animal model (Gallus domesticus) for ICRS surgery (Ferrara technique). The animals without complications were randomized to two groups; in all of them, 1 segment was implanted in each eye and later removed at different times (1 and 3 months after implantation). In each group, after explantation, corneas were processed at different times for histological analysis with hematoxylin and eosin (H&E) stain and electronic microscopy. The refractive state of the eyes was also measured. RESULTS In corneas without complications (88.23%), explantation was performed correctly. During the first few days, around the area where the ICRS was implanted we observed deposits of cells and a moderate degree of corneal opacity (haze). These signs decreased progressively without disappearing completely. Histologically, at 7 days, we observed hyperplasia and abnormal arrangement of collagen fibers. Later, these findings also decreased in both groups, albeit at a faster rate in group 1. Minimal changes were observed in electron microscopy up to the end of the study in both groups. Preoperative refractive state was achieved at 1 month after explantation in both groups. CONCLUSIONS ICRS can safely be explanted from the cornea. Refractive reversibility was achieved at 1 month after explantation. However, the clinical and histological findings after ICRS explantation depend on the time from implantation to explantation.
Collapse
Affiliation(s)
- Lucía Ibares-Frías
- a Optical Diagnostic Techniques Group, Theoretical, Atomic and Optical Physics Department , University of Valladolid , Valladolid , Spain.,b Ophthalmology Department , Hospital Clínico Universitario de Valladolid , Valladolid , Spain
| | - Patricia Gallego
- a Optical Diagnostic Techniques Group, Theoretical, Atomic and Optical Physics Department , University of Valladolid , Valladolid , Spain.,c Cell Biology, Histology and Pharmacology Department , Faculty of Medicine, University of Valladolid , Valladolid , Spain
| | | | - Jesús Merayo-Lloves
- a Optical Diagnostic Techniques Group, Theoretical, Atomic and Optical Physics Department , University of Valladolid , Valladolid , Spain.,d Instituto Universitario Fernandez-Vega, Universidad de Oviedo , Oviedo , Spain
| | - María Carmen Martínez-García
- a Optical Diagnostic Techniques Group, Theoretical, Atomic and Optical Physics Department , University of Valladolid , Valladolid , Spain.,c Cell Biology, Histology and Pharmacology Department , Faculty of Medicine, University of Valladolid , Valladolid , Spain
| |
Collapse
|
25
|
Ávila FJ, Bueno JM. Analysis and quantification of collagen organization with the structure tensor in second harmonic microscopy images of ocular tissues. APPLIED OPTICS 2015; 54:9848-54. [PMID: 26836548 DOI: 10.1364/ao.54.009848] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The important biological role of collagen-based tissues and the changes produced in the fiber distribution under particular situations (surgery, pathology, external damage, etc.) require tools for the analysis of the collagen organization that might potentially help in early diagnoses. Since collagen structures provide efficient second harmonic generation (SHG) signals, SHG microscopy has emerged as a powerful technique to visualize collagen fibers and qualitatively discriminate normal from abnormal tissues. Here we propose a quantitative method based on the structure tensor to quantify the different organization of collagen patterns in SHG images of ocular tissues. Results show that well-organized collagen distributions present a high degree of isotropy (DoI), a dominant orientation (PO), and a low structural dispersion (SD). On the other hand, the PO vanishes when the collagen tissue is not organized as a consequence of an increase in the SD and a decrease in the DoI. The proposed method is also able to discriminate partially organized samples. The combination of SHG microscopy and the structure tensor is a useful method to objectively classify collagen distributions. Clinical applications of this technique could help in the diagnosis and tracking of pathologies related to collagen disorders in connective tissue.
Collapse
|
26
|
Park CY, Lee JK, Chuck RS. Second Harmonic Generation Imaging Analysis of Collagen Arrangement in Human Cornea. Invest Ophthalmol Vis Sci 2015; 56:5622-9. [PMID: 26313297 DOI: 10.1167/iovs.15-17129] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To describe the horizontal arrangement of human corneal collagen bundles by using second harmonic generation (SHG) imaging. METHODS Human corneas were imaged with an inverted two photon excitation fluorescence microscope. The excitation laser (Ti:Sapphire) was tuned to 850 nm. Backscatter signals of SHG were collected through a 425/30-nm bandpass emission filter. Multiple, consecutive, and overlapping image stacks (z-stacks) were acquired to generate three dimensional data sets. ImageJ software was used to analyze the arrangement pattern (irregularity) of collagen bundles at each image plane. RESULTS Collagen bundles in the corneal lamellae demonstrated a complex layout merging and splitting within a single lamellar plane. The patterns were significantly different in the superficial and limbal cornea when compared with deep and central regions. Collagen bundles were smaller in the superficial layer and larger in deep lamellae. CONCLUSIONS By using SHG imaging, the horizontal arrangement of corneal collagen bundles was elucidated at different depths and focal regions of the human cornea.
Collapse
Affiliation(s)
- Choul Yong Park
- Department of Ophthalmology Dongguk University, Ilsan Hospital, Goyang, Kyunggido, South Korea 2Department of Ophthalmology and Visual Sciences, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, New York, United States
| | - Jimmy K Lee
- Department of Ophthalmology and Visual Sciences, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, New York, United States
| | - Roy S Chuck
- Department of Ophthalmology and Visual Sciences, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, New York, United States
| |
Collapse
|
27
|
SKORSETZ MARTIN, ARTAL PABLO, BUENO JUANM. Performance evaluation of a sensorless adaptive optics multiphoton microscope. J Microsc 2015; 261:249-58. [DOI: 10.1111/jmi.12325] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 09/02/2015] [Indexed: 01/26/2023]
Affiliation(s)
- MARTIN SKORSETZ
- 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
|
28
|
Park CY, Lee JK, Zhang C, Chuck RS. New Details of the Human Corneal Limbus Revealed With Second Harmonic Generation Imaging. Invest Ophthalmol Vis Sci 2015; 56:6058-66. [PMID: 26393473 DOI: 10.1167/iovs.15-16783] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To report novel findings of the human corneal limbus by using second harmonic generation (SHG) imaging. METHODS Corneal limbus was imaged by using an inverted two-photon excitation fluorescence microscope. Laser (Ti:Sapphire) was tuned at 850 nm for two-photon excitation. Backscatter signals of SHG and autofluorescence (AF) were collected through a 425/30-nm emission filter and a 525/45-emission filter, respectively. Multiple, consecutive, and overlapping image stacks (z-stack) were acquired for the corneal limbal area. RESULTS Two novel collagen structures were revealed by SHG imaging at the limbus: an anterior limbal cribriform layer and presumed anchoring fibers. Anterior limbal cribriform layer is an intertwined reticular collagen architecture just beneath the limbal epithelial niche and is located between the peripheral cornea and Tenon's/scleral tissue. Autofluorescence imaging revealed high vascularity in this structure. Central to the anterior limbal cribriform layer, radial strands of collagen were found to connect the peripheral cornea to the limbus. These presumed anchoring fibers have both collagen and elastin and were found more extensively in the superficial layers than deep layer and were absent in very deep limbus near Schlemm's canal. CONCLUSIONS By using SHG imaging, new details of the collagen architecture of human corneal limbal area were elucidated. High resolution images with volumetric analysis revealed two novel collagen structures.
Collapse
Affiliation(s)
- Choul Yong Park
- Department of Ophthalmology, Dongguk University, Ilsan Hospital, Goyang, Kyunggido, South Korea 2Department of Ophthalmology and Visual Sciences, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, New York, United States
| | - Jimmy K Lee
- Department of Ophthalmology and Visual Sciences, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, New York, United States
| | - Cheng Zhang
- Department of Ophthalmology and Visual Sciences, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, New York, United States
| | - Roy S Chuck
- Department of Ophthalmology and Visual Sciences, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, New York, United States
| |
Collapse
|
29
|
Meek KM, Knupp C. Corneal structure and transparency. Prog Retin Eye Res 2015; 49:1-16. [PMID: 26145225 PMCID: PMC4655862 DOI: 10.1016/j.preteyeres.2015.07.001] [Citation(s) in RCA: 454] [Impact Index Per Article: 50.4] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 06/28/2015] [Accepted: 07/01/2015] [Indexed: 12/13/2022]
Abstract
The corneal stroma plays several pivotal roles within the eye. Optically, it is the main refracting lens and thus has to combine almost perfect transmission of visible light with precise shape, in order to focus incoming light. Furthermore, mechanically it has to be extremely tough to protect the inner contents of the eye. These functions are governed by its structure at all hierarchical levels. The basic principles of corneal structure and transparency have been known for some time, but in recent years X-ray scattering and other methods have revealed that the details of this structure are far more complex than previously thought and that the intricacy of the arrangement of the collagenous lamellae provides the shape and the mechanical properties of the tissue. At the molecular level, modern technologies and theoretical modelling have started to explain exactly how the collagen fibrils are arranged within the stromal lamellae and how proteoglycans maintain this ultrastructure. In this review we describe the current state of knowledge about the three-dimensional stromal architecture at the microscopic level, and about the control mechanisms at the nanoscopic level that lead to optical transparency.
Collapse
Affiliation(s)
- Keith M Meek
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff CF24 4HQ, UK.
| | - Carlo Knupp
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff CF24 4HQ, UK
| |
Collapse
|
30
|
Bueno JM, Palacios R, Pennos A, Artal P. Second-harmonic generation microscopy of photocurable polymer intrastromal implants in ex-vivo corneas. BIOMEDICAL OPTICS EXPRESS 2015; 6:2211-9. [PMID: 26114039 PMCID: PMC4473754 DOI: 10.1364/boe.6.002211] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 05/14/2015] [Accepted: 05/14/2015] [Indexed: 05/25/2023]
Abstract
A custom adaptive-optics (AO) multiphoton microscope was used to visualize the corneal stroma after the insertion of a photocurable polymer material. A lamellar pocket was created and a certain amount of polymer in liquid form was injected. This turned into a rigid film after UV irradiation. Intact eyes were used as control. Tomographic and regular second harmonic generation (SHG) microscopy images were recorded from both control and corneas with polymer implants. In control corneas, the SHG signal decreased uniformly with depth. However, treated corneas exhibited an abrupt loss of SHG signal at the implant location. The use of AO increased the SHG levels and improved the visualization of the stroma, not only at deeper corneal layers but also beneath the implant. Moreover, the absence of SHG signal from the implant allowed its geometrical characterization (thickness and location). This technique offers a potential tool for non-invasive analysis of morphological changes in the cornea after surgery or treatment, and might be useful in future clinical environments.
Collapse
|
31
|
Calhoun WR, Ilev IK. Effect of therapeutic femtosecond laser pulse energy, repetition rate, and numerical aperture on laser-induced second and third harmonic generation in corneal tissue. Lasers Med Sci 2015; 30:1341-6. [DOI: 10.1007/s10103-015-1726-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 02/16/2015] [Indexed: 10/23/2022]
|
32
|
Lombardo G, Serrao S, Rosati M, Lombardo M. Analysis of the viscoelastic properties of the human cornea using Scheimpflug imaging in inflation experiment of eye globes. PLoS One 2014; 9:e112169. [PMID: 25397674 PMCID: PMC4232387 DOI: 10.1371/journal.pone.0112169] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Accepted: 10/13/2014] [Indexed: 11/18/2022] Open
Abstract
PURPOSE To demonstrate a Scheimpflug-based imaging procedure for investigating the depth- and time-dependent strain response of the human cornea to inflation testing of whole eye globes. METHODS Six specimens, three of which with intact corneal epithelium, were mounted in a customized apparatus within a humidity and temperature-monitored wet chamber. Each specimen was subjected to two mechanical tests in order to measure corneal strain resulting from application of cyclic (cyclic regimen) and constant (creep regimen) stress by changing the intra-ocular pressure (IOP) within physiological ranges (18-42 mmHg). Corneal shape changes were analyzed as a function of IOP and both corneal stress-strain curves and creep curves were generated. RESULTS The procedure was highly accurate and repeatable. Upon cyclic stress application, a biomechanical corneal elasticity gradient was found in the front-back direction. The average Young's modulus of the anterior cornea ranged between 2.28±0.87 MPa and 3.30±0.90 MPa in specimens with and without intact epithelium (P = 0.05) respectively. The Young's modulus of the posterior cornea was on average 0.21±0.09 MPa and 0.17±0.06 MPa (P>0.05) respectively. The time-dependent strain response of the cornea to creep testing was quantified by fitting data to a modified Zener model for extracting both the relaxation time and compliance function. CONCLUSION Cyclic and creep mechanical tests are valuable for investigating the strain response of the intact human cornea within physiological IOP ranges, providing meaningful results that can be translated to clinic. The presence of epithelium influences the results of anterior corneal shape changes when monitoring deformation via Scheimpflug imaging in inflation experiments of whole eye globes.
Collapse
Affiliation(s)
- Giuseppe Lombardo
- CNR-IPCF, Unit of Support of Cosenza, Ponte P. Bucci, 87036 Rende, Italy
- Vision Engineering Italy S.r.l., Via Adda 7, 00198 Rome, Italy
- * E-mail: (ML); (GL)
| | | | - Marianna Rosati
- Fondazione G.B. Bietti IRCCS, Via Livenza 3, 00198 Rome, Italy
| | - Marco Lombardo
- Fondazione G.B. Bietti IRCCS, Via Livenza 3, 00198 Rome, Italy
- * E-mail: (ML); (GL)
| |
Collapse
|
33
|
Lai T, Tang S. Cornea characterization using a combined multiphoton microscopy and optical coherence tomography system. BIOMEDICAL OPTICS EXPRESS 2014; 5:1494-511. [PMID: 24877011 PMCID: PMC4026894 DOI: 10.1364/boe.5.001494] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 03/30/2014] [Accepted: 04/04/2014] [Indexed: 05/17/2023]
Abstract
We present a multimodal imaging system which combines multiphoton microscopy and optical coherence tomography to visualize the morphological structures, and to quantify the refractive index (RI) and thickness of cornea. The morphological similarities and differences at different corneal layers across various species are identified. In the piscine and human corneas, the stromata exhibit thin fibers that indicate an overall collagen direction. Human corneas display collagen micro-folds which cause increased light attenuation. In the murine, porcine and bovine corneas, the stromata show interwoven collagen patterns. The Bowman's layer and the Descemet's membrane are also distinguished in some species. The RI and thicknesses are quantified for the epithelium and the stromal layers respectively, where the epithelium is found to have slightly higher RI than the stroma. The average epithelial and stromal RI are, respectively, 1.371 ± 0.016 and 1.360 ± 0.008 for the murine corneas; 1.502 ± 0.057 and 1.335 ± 0.011 for the piscine corneas; 1.433 ± 0.023 and 1.357 ± 0.013 for the human corneas; 1.476 ± 0.091 and 1.343 ± 0.013 for the porcine corneas; and 1.400 ± 0.007 and 1.376 ± 0.003 for the bovine corneas. The multimodal system can potentially provide a comprehensive characterization of the cornea.
Collapse
|
34
|
Second-Harmonic Reflection Imaging of Normal and Accelerated Corneal Crosslinking Using Porcine Corneas and the Role of Intraocular Pressure. Cornea 2014; 33:125-30. [DOI: 10.1097/ico.0000000000000015] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
35
|
Thomasy SM, Raghunathan VK, Winkler M, Reilly CM, Sadeli AR, Russell P, Jester JV, Murphy CJ. Elastic modulus and collagen organization of the rabbit cornea: epithelium to endothelium. Acta Biomater 2014; 10:785-91. [PMID: 24084333 DOI: 10.1016/j.actbio.2013.09.025] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Revised: 08/08/2013] [Accepted: 09/06/2013] [Indexed: 12/21/2022]
Abstract
The rabbit is commonly used to evaluate new corneal prosthetics and study corneal wound healing. Knowledge of the stiffness of the rabbit cornea would better inform the design and fabrication of keratoprosthetics and substrates with relevant mechanical properties for in vitro investigations of corneal cellular behavior. This study determined the elastic modulus of the rabbit corneal epithelium, anterior basement membrane (ABM), anterior and posterior stroma, Descemet's membrane (DM) and endothelium using atomic force microscopy (AFM). In addition, three-dimensional collagen fiber organization of the rabbit cornea was determined using nonlinear optical high-resolution macroscopy. The elastic modulus as determined by AFM for each corneal layer was: epithelium, 0.57 ± 0.29 kPa (mean ± SD); ABM, 4.5 ± 1.2 kPa, anterior stroma, 1.1 ± 0.6 kPa; posterior stroma, 0.38 ± 0.22 kPa; DM, 11.7 ± 7.4 kPa; and endothelium, 4.1 ± 1.7 kPa. The biophysical properties, including the elastic modulus, are unique for each layer of the rabbit cornea and are dramatically softer in comparison to the corresponding regions of the human cornea. Collagen fiber organization is also dramatically different between the two species, with markedly less intertwining observed in the rabbit vs. human cornea. Given that the substratum stiffness considerably alters the corneal cell behavior, keratoprosthetics that incorporate mechanical properties simulating the native human cornea may not elicit optimal cellular performance in rabbit corneas that have dramatically different elastic moduli. These data should allow for the design of substrates that better mimic the biomechanical properties of the corneal cellular environment.
Collapse
Affiliation(s)
- Sara M Thomasy
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616, USA
| | - Vijay Krishna Raghunathan
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616, USA
| | - Moritz Winkler
- Department of Biomedical Engineering, University of California-Irvine, Irvine, CA, USA
| | - Christopher M Reilly
- Department of Pathology, Immunology and Microbiology, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616, USA
| | - Adeline R Sadeli
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616, USA
| | - Paul Russell
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616, USA
| | - James V Jester
- Department of Biomedical Engineering, University of California-Irvine, Irvine, CA, USA
| | - Christopher J Murphy
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616, USA; Department of Ophthalmology and Vision Science, School of Medicine, University of California-Davis, Davis, CA 95616, USA.
| |
Collapse
|
36
|
Meyer T, Schmitt M, Dietzek B, Popp J. Accumulating advantages, reducing limitations: multimodal nonlinear imaging in biomedical sciences - the synergy of multiple contrast mechanisms. JOURNAL OF BIOPHOTONICS 2013; 6:887-904. [PMID: 24259267 DOI: 10.1002/jbio.201300176] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Accepted: 11/06/2013] [Indexed: 05/29/2023]
Abstract
Multimodal nonlinear microscopy has matured during the past decades to one of the key imaging modalities in life science and biomedicine due to its unique capabilities of label-free visualization of tissue structure and chemical composition, high depth penetration, intrinsic 3D sectioning, diffraction limited resolution and low phototoxicity. This review briefly summarizes first recent advances in the field regarding the methodology, e.g., contrast mechanisms and signal characteristics used for contrast generation as well as novel image processing approaches. The second part deals with technologic developments emphasizing improvements in penetration depth, imaging speed, spatial resolution and nonlinear labeling strategies. The third part focuses on recent applications in life science fundamental research and biomedical diagnostics as well as future clinical applications.
Collapse
Affiliation(s)
- Tobias Meyer
- Institute of Physical Chemistry and Abbe Center of Photonics, Friedrich-Schiller-University Jena, Helmholtzweg 4, 07743 Jena, Germany
| | | | | | | |
Collapse
|
37
|
Ammar DA, Lei TC, Kahook MY, Masihzadeh O. Imaging the intact mouse cornea using coherent anti-stokes Raman scattering (CARS). Invest Ophthalmol Vis Sci 2013; 54:5258-65. [PMID: 23821187 DOI: 10.1167/iovs.12-11513] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
PURPOSE The aim of this study was to image the cellular and noncellular structures of the cornea and limbus in an intact mouse eye using the vibrational oscillation of the carbon-hydrogen bond in lipid membranes and autofluorescence as label-free contrast agents. METHODS Freshly enucleated mouse eyes were imaged using two nonlinear optical techniques: coherent anti-Stokes Raman scattering (CARS) and two-photon autofluorescence (TPAF). Sequential images were collected through the full thickness of the cornea and limbal regions. Line scans along the transverse/sagittal axes were also performed. RESULTS Analysis of multiple CARS/TPAF images revealed that corneal epithelial and endothelial cells could be identified by the lipid-rich plasma membrane CARS signal. The fluorescent signal from the collagen fibers of the corneal stroma was evident in the TPAF channel. The transition from the cornea to sclera at the limbus was marked by a change in collagen pattern (TPAF channel) and thickness of surface cells (CARS channel). Regions within the corneal stroma that lack collagen autofluorescence coincided with CARS signal, indicating the presence of stromal fibroblasts or nerve fibers. CONCLUSIONS The CARS technique was successful in imaging cells in the intact mouse eye, both at the surface and within corneal tissue. Multiphoton images were comparable to histologic sections. The methods described here represent a new avenue for molecular specific imaging of the mouse eye. The lack of need for tissue fixation is unique compared with traditional histology imaging techniques.
Collapse
Affiliation(s)
- David A Ammar
- Department of Ophthalmology, University of Colorado Denver, Aurora, Colorado 80045, USA
| | | | | | | |
Collapse
|
38
|
Bueno JM, Palacios R, Chessey MK, Ginis H. Analysis of spatial lamellar distribution from adaptive-optics second harmonic generation corneal images. BIOMEDICAL OPTICS EXPRESS 2013; 4:1006-13. [PMID: 23847727 PMCID: PMC3704083 DOI: 10.1364/boe.4.001006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Revised: 04/24/2013] [Accepted: 04/24/2013] [Indexed: 05/20/2023]
Abstract
The spatial organization of stromal collagen of ex-vivo corneas has been quantified in adaptive-optics second harmonic generation (SHG) images by means of an optimized Fourier transform (FT) based analysis. At a particular depth location, adjacent lamellae often present similar orientations and run parallel to the corneal surface. However this pattern might be combined with interweaved collagen bundles leading to crosshatched structures with different orientations. The procedure here reported provides us with both principal and crosshatched angles. This is also able to automatically distinguish a random distribution from a cross-shaped one, since it uses the ratio of the axes lengths of the best-fitted ellipse of the FT data as an auxiliary parameter. The technique has successfully been applied to SHG images of healthy corneas (both stroma and Bowman's layer) of different species and to corneas undergoing cross-linking treatment.
Collapse
|
39
|
Scarcelli G, Pineda R, Yun SH. Brillouin optical microscopy for corneal biomechanics. Invest Ophthalmol Vis Sci 2012; 53:185-90. [PMID: 22159012 DOI: 10.1167/iovs.11-8281] [Citation(s) in RCA: 180] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE The mechanical properties of corneal tissue are linked to prevalent ocular diseases and therapeutic procedures. Brillouin microscopy is a novel optical technology that enables three-dimensional mechanical imaging. In this study, the feasibility of this noncontact technique was tested for in situ quantitative assessment of the biomechanical properties of the cornea. METHODS Brillouin light-scattering involves a spectral shift proportional to the longitudinal modulus of elasticity of the tissue. A 532-nm single-frequency laser and a custom-developed ultrahigh-resolution spectrometer were used to measure the Brillouin frequency. Confocal scanning was used to perform Brillouin elasticity imaging of the corneas of whole bovine eyes. The longitudinal modulus of the bovine corneas was compared before and after riboflavin corneal collagen photo-cross-linking. The Brillouin measurements were then compared with conventional stress-strain mechanical test results. RESULTS High-resolution Brillouin images of the cornea were obtained, revealing a striking depth-dependent variation of the elastic modulus across the cornea. Along the central axis, the Brillouin frequency shift varied gradually from 8.2 GHz in the epithelium to 7.5 GHz near the endothelium. The coefficients of the down slope were measured to be approximately 1.09, 0.32, and 2.94 GHz/mm in the anterior, posterior, and innermost stroma, respectively. On riboflavin collagen cross-linking, marked changes in the axial Brillouin profiles (P < 0.001) were noted before and after cross-linking. CONCLUSIONS Brillouin imaging can assess the biomechanical properties of cornea in situ with high spatial resolution. This novel technique has the potential for use in clinical diagnostics and treatment monitoring.
Collapse
Affiliation(s)
- Giuliano Scarcelli
- Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, Massachusetts, USA
| | | | | |
Collapse
|
40
|
Gualda EJ, Vázquez de Aldana JR, Martínez-García MC, Moreno P, Hernández-Toro J, Roso L, Artal P, Bueno JM. Femtosecond infrared intrastromal ablation and backscattering-mode adaptive-optics multiphoton microscopy in chicken corneas. BIOMEDICAL OPTICS EXPRESS 2011; 2:2950-60. [PMID: 22076258 PMCID: PMC3207366 DOI: 10.1364/boe.2.002950] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Revised: 09/27/2011] [Accepted: 09/27/2011] [Indexed: 05/07/2023]
Abstract
The performance of femtosecond (fs) laser intrastromal ablation was evaluated with backscattering-mode adaptive-optics multiphoton microscopy in ex vivo chicken corneas. The pulse energy of the fs source used for ablation was set to generate two different ablation patterns within the corneal stroma at a certain depth. Intrastromal patterns were imaged with a custom adaptive-optics multiphoton microscope to determine the accuracy of the procedure and verify the outcomes. This study demonstrates the potential of using fs pulses as surgical and monitoring techniques to systematically investigate intratissue ablation. Further refinement of the experimental system by combining both functions into a single fs laser system would be the basis to establish new techniques capable of monitoring corneal surgery without labeling in real-time. Since the backscattering configuration has also been optimized, future in vivo implementations would also be of interest in clinical environments involving corneal ablation procedures.
Collapse
Affiliation(s)
- Emilio J. Gualda
- Laboratorio de Óptica, Centro de Investigación en Óptica y Nanofísica, Universidad de Murcia, Campus de Espinardo (Edificio 34), 30100 Murcia, Spain
| | - Javier R. Vázquez de Aldana
- Grupo de Investigación en Microprocesado de Materiales con Láser,Plaza de la Merced s/n, 37008 Salamanca, Spain
| | - M. Carmen Martínez-García
- Departamento Biología Celular, Histología y Farmacología,Facultad de Medicina, Universidad de Valladolid, Valladolid, Spain
| | - Pablo Moreno
- Grupo de Investigación en Microprocesado de Materiales con Láser,Plaza de la Merced s/n, 37008 Salamanca, Spain
| | - Juan Hernández-Toro
- Grupo de Investigación en Microprocesado de Materiales con Láser,Plaza de la Merced s/n, 37008 Salamanca, Spain
| | - Luis Roso
- Centro de Láseres Pulsados Ultracortos y Ultraintensos (CLPU), Plaza de la Merced s/n, 37008 Salamanca, Spain
| | - Pablo Artal
- Laboratorio de Óptica, Centro de Investigación en Óptica y Nanofísica, Universidad de Murcia, Campus de Espinardo (Edificio 34), 30100 Murcia, Spain
| | - Juan M. Bueno
- Laboratorio de Óptica, Centro de Investigación en Óptica y Nanofísica, Universidad de Murcia, Campus de Espinardo (Edificio 34), 30100 Murcia, Spain
| |
Collapse
|
41
|
Bueno JM, Giakoumaki A, Gualda EJ, Schaeffel F, Artal P. Analysis of the chicken retina with an adaptive optics multiphoton microscope. BIOMEDICAL OPTICS EXPRESS 2011; 2:1637-48. [PMID: 21698025 PMCID: PMC3114230 DOI: 10.1364/boe.2.001637] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Revised: 05/13/2011] [Accepted: 05/13/2011] [Indexed: 05/23/2023]
Abstract
The structure and organization of the chicken retina has been investigated with an adaptive optics multiphoton imaging microscope in a backward configuration. Non-stained flat-mounted retinal tissues were imaged at different depths, from the retinal nerve fiber layer to the outer segment, by detecting the intrinsic nonlinear fluorescent signal. From the stacks of images corresponding to the different retinal layers, volume renderings of the entire retina were reconstructed. The density of photoreceptors and ganglion cells layer were directly estimated from the images as a function of the retinal eccentricity. The maximum anatomical resolving power at different retinal eccentricities was also calculated. This technique could be used for a better characterization of retinal alterations during myopia development, and may be useful for visualization of retinal pathologies and intoxication during pharmacological studies.
Collapse
Affiliation(s)
- Juan M. Bueno
- Laboratorio de Óptica, Centro de Investigación en Óptica y Nanofísica, Universidad de Murcia, Campus de Espinardo (Edificio 34), 30100 Murcia, Spain
| | - Anastasia Giakoumaki
- Laboratorio de Óptica, Centro de Investigación en Óptica y Nanofísica, Universidad de Murcia, Campus de Espinardo (Edificio 34), 30100 Murcia, Spain
| | - Emilio J. Gualda
- Laboratorio de Óptica, Centro de Investigación en Óptica y Nanofísica, Universidad de Murcia, Campus de Espinardo (Edificio 34), 30100 Murcia, Spain
| | - Frank Schaeffel
- Section of Neurobiology of the Eye, Ophthalmic Research Institute, Calwerstrasse 7/1, 72076 Tuebingen, Germany
| | - Pablo Artal
- Laboratorio de Óptica, Centro de Investigación en Óptica y Nanofísica, Universidad de Murcia, Campus de Espinardo (Edificio 34), 30100 Murcia, Spain
| |
Collapse
|