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van Koeverden AK, Afiat BC, Nguyen CT, Bui BV, Lee PY. Understanding how ageing impacts ganglion cell susceptibility to injury in glaucoma. Clin Exp Optom 2024; 107:147-155. [PMID: 37980904 DOI: 10.1080/08164622.2023.2279734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2023] [Accepted: 10/31/2023] [Indexed: 11/21/2023] Open
Abstract
Glaucoma is a leading cause of blindness worldwide, with a marked increase in prevalence with advancing age. Due to the multifactorial nature of glaucoma pathogenesis, dissecting how ageing impacts upon glaucoma risk requires analysis and synthesis of evidence from a vast literature. While there is a wealth of human clinical studies examining glaucoma pathogenesis and why older patients have increased risk, many aspects of the disease such as adaptations of retinal ganglion cells to stress, autophagy and the role of glial cells in glaucoma, require the use of animal models to study the complex cellular processes and interactions. Additionally, the accelerated nature of ageing in rodents facilitates the longitudinal study of changes that would not be feasible in human clinical studies. This review article examines evidence derived predominantly from rodent models on how the ageing process impacts upon various aspects of glaucoma pathology from the retinal ganglion cells themselves, to supporting cells and tissues such as glial cells, connective tissue and vasculature, in addition to oxidative stress and autophagy. An improved understanding of how ageing modifies these factors may lead to the development of different therapeutic strategies that target specific risk factors or processes involved in glaucoma.
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Affiliation(s)
- Anna K van Koeverden
- Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria, Australia
| | - Brianna C Afiat
- Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria, Australia
| | - Christine To Nguyen
- Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria, Australia
| | - Bang V Bui
- Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria, Australia
| | - Pei Ying Lee
- Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria, Australia
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Korneva A, Kimball EC, Johnson TV, Quillen SE, Pease ME, Quigley HA, Nguyen TD. Comparison of the Biomechanics of the Mouse Astrocytic Lamina Cribrosa Between Glaucoma and Optic Nerve Crush Models. Invest Ophthalmol Vis Sci 2023; 64:14. [PMID: 38088825 PMCID: PMC10720758 DOI: 10.1167/iovs.64.15.14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 11/14/2023] [Indexed: 12/17/2023] Open
Abstract
Purpose The strain response of the mouse astrocytic lamina (AL) to an ex vivo mechanical test was compared between two protocols: eyes that underwent sustained intraocular pressure (IOP) increase and eyes after optic nerve crush. Methods Chronic IOP elevation was induced by microbead injection or the optic nerve was crushed in mice with widespread green fluorescence. After 3 days or 6 weeks, eyes were inflation tested by a published method of two-photon fluorescence to image the AL. Digital volume correlation was used to calculate strains. Optic nerve axon damage was also evaluated. Results In the central AL but not the peripheral AL, four strains were greater in eyes at the 3-day glaucoma time point than control (P from 0.029 to 0.049, n = 8 eyes per group). Also, at this time point, five strains were greater in the central AL compared to the peripheral AL (P from 0.041 to 0.00003). At the 6-week glaucoma time point, the strains averaged across the specimen, in the central AL, and the peripheral AL were indistinguishable from the respective controls. Strains were not significantly different between controls and eyes 3 days or 6 weeks after crush (n = 8 and 16). Conclusions We found alterations in the ex vivo mechanical behavior in eyes from mice with experimental glaucoma but not in those with crushed optic nerves. The results of this study demonstrate that significant axon injury does not directly affect mechanical behavior of the astrocytic lamina.
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Affiliation(s)
- Arina Korneva
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - Elizabeth C. Kimball
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - Thomas V. Johnson
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - Sarah E. Quillen
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - Mary E. Pease
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - Harry A. Quigley
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - Thao D. Nguyen
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
- Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, Maryland, United States
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Ling YTT, Korneva A, Quigley HA, Nguyen TD. Computational study of the mechanical behavior of the astrocyte network and axonal compartments in the mouse optic nerve head. Biomech Model Mechanobiol 2023; 22:1751-1772. [PMID: 37573553 PMCID: PMC10988382 DOI: 10.1007/s10237-023-01752-z] [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: 10/01/2022] [Accepted: 07/15/2023] [Indexed: 08/15/2023]
Abstract
Glaucoma is a blinding disease characterized by the degeneration of the retinal ganglion cell (RGC) axons at the optic nerve head (ONH). A major risk factor for glaucoma is the intraocular pressure (IOP). However, it is currently impossible to measure the IOP-induced mechanical response of the axons of the ONH. The objective of this study was to develop a computational modeling method to estimate the IOP-induced strains and stresses in the axonal compartments in the mouse astrocytic lamina (AL) of the ONH, and to investigate the effect of the structural features on the mechanical behavior. We developed experimentally informed finite element (FE) models of six mouse ALs to investigate the effect of structure on the strain responses of the astrocyte network and axonal compartments to pressure elevation. The specimen-specific geometries of the FE models were reconstructed from confocal fluorescent images of cryosections of the mouse AL acquired in a previous study that measured the structural features of the astrocytic processes and axonal compartments. The displacement fields obtained from digital volume correlation in prior inflation tests of the mouse AL were used to determine the displacement boundary conditions of the FE models. We then applied Gaussian process regression to analyze the effects of the structural features on the strain outcomes simulated for the axonal compartments. The axonal compartments experienced, on average, 6 times higher maximum principal strain but 1800 times lower maximum principal stress compared to those experienced by the astrocyte processes. The strains experienced by the axonal compartments were most sensitive to variations in the area of the axonal compartments. Larger axonal compartments that were more vertically aligned, closer to the AL center, and with lower local actin area fraction had higher strains. Understanding the factors affecting the deformation in the axonal compartments will provide insights into mechanisms of glaucomatous axonal damage.
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Affiliation(s)
- Yik Tung Tracy Ling
- Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD, USA
| | - Arina Korneva
- Department of Ophthalmology, Johns Hopkins School of Medicine, Baltimore, MD, USA
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Harry A Quigley
- Department of Ophthalmology, Johns Hopkins School of Medicine, Baltimore, MD, USA
- Glaucoma Center of Excellence, Wilmer Eye Institute, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Thao D Nguyen
- Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD, USA.
- Department of Ophthalmology, Johns Hopkins School of Medicine, Baltimore, MD, USA.
- Department of Materials Science, Johns Hopkins University, Baltimore, MD, USA.
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Czerpak CA, Kashaf MS, Zimmerman BK, Quigley HA, Nguyen TD. The Strain Response to Intraocular Pressure Decrease in the Lamina Cribrosa of Patients with Glaucoma. Ophthalmol Glaucoma 2023; 6:11-22. [PMID: 35863747 PMCID: PMC9849479 DOI: 10.1016/j.ogla.2022.07.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 07/11/2022] [Accepted: 07/12/2022] [Indexed: 01/27/2023]
Abstract
OBJECTIVE To measure biomechanical strains in the lamina cribrosa (LC) of living human eyes with intraocular pressure (IOP) lowering. DESIGN Cohort study. PARTICIPANTS Patients with glaucoma underwent imaging before and after laser suturelysis after trabeculectomy surgery (29 image pairs; 26 persons). INTERVENTION Noninvasive imaging of the eye. MAIN OUTCOME MEASURES Strains in optic nerve head tissue and changes in depths of the anterior border of the LC. RESULTS Intraocular pressure decreases caused the LC to expand in thickness in the anterior-posterior strain (Ezz = 0.94 ± 1.2%; P = 0.00020) and contract in radius in the radial strain (Err = - 0.19 ± 0.33%; P = 0.0043). The mean LC depth did not significantly change with IOP lowering (1.33 ± 6.26 μm; P = 0.26). A larger IOP decrease produced a larger, more tensile Ezz (P < 0.0001), greater maximum principal strain (Emax; P < 0.0001), and greater maximum shear strain (Γmax; P < 0.0001). The average LC depth change was associated with the Γmax and radial-circumferential shear strain (Erθ; P < 0.02) but was not significantly related to tensile or compressive strains. An analysis by clock hour showed that in temporal clock hours 3 to 6, a more anterior LC movement was associated with a more positive Emax, and in clock hours 3, 5, and 6, it was associated with a more positive Γmax. At 10 o'clock, a more posterior LC movement was related to a more positive Emax (P < 0.004). Greater compliance (strain/ΔIOP) of Emax (P = 0.044), Γmax (P = 0.052), and Erθ (P = 0.018) was associated with a thinner retinal nerve fiber layer. Greater compliance of Emax (P = 0.041), Γmax (P = 0.021), Erθ (P = 0.024), and in-plane shear strain (Erz; P = 0.0069) was associated with more negative mean deviations. Greater compliance of Γmax (P = 0.055), Erθ (P = 0.040), and Erz (P = 0.015) was associated with lower visual field indices. CONCLUSIONS With IOP lowering, the LC moves either into or out of the eye but, on average, expands in thickness and contracts in radius. Shear strains are nearly as substantial as in-plane strains. Biomechanical strains are more compliant in eyes with greater glaucoma damage. This work was registered at ClinicalTrials.gov as NCT03267849.
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Affiliation(s)
- Cameron A Czerpak
- Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, Maryland.
| | - Michael Saheb Kashaf
- Wilmer Ophthalmological Institute, School of Medicine, The Johns Hopkins University, Baltimore, Maryland
| | - Brandon K Zimmerman
- Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, Maryland
| | - Harry A Quigley
- Wilmer Ophthalmological Institute, School of Medicine, The Johns Hopkins University, Baltimore, Maryland
| | - Thao D Nguyen
- Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, Maryland; Wilmer Ophthalmological Institute, School of Medicine, The Johns Hopkins University, Baltimore, Maryland
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Qiu C, Wang C, Sun X, Xu J, Wu J, Zhang R, Li G, Xue K, Zhang X, Qian S. CXC‐ receptor 2 promotes extracellular matrix production and attenuates migration in peripapillary human scleral fibroblasts under mechanical strain. J Cell Mol Med 2022; 26:5858-5871. [DOI: 10.1111/jcmm.17609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 10/15/2022] [Accepted: 10/21/2022] [Indexed: 11/11/2022] Open
Affiliation(s)
- Chen Qiu
- Department of Ophthalmology and Vision Science, Eye and Ear, Nose, Throat Hospital, Shanghai Medical College Fudan University Shanghai China
- NHC Key Laboratory of Myopia Fudan University Shanghai China
- Laboratory of Myopia Chinese Academy of Medical Sciences Shanghai China
- Shanghai Key Laboratory of Visual Impairment and Restoration Fudan University Shanghai China
| | - Chuandong Wang
- Department of Orthopedic Surgery Xin Hua Hospital Affiliated to Shanghai Jiaotong University School of Medicine Shanghai China
| | - Xinghuai Sun
- Department of Ophthalmology and Vision Science, Eye and Ear, Nose, Throat Hospital, Shanghai Medical College Fudan University Shanghai China
- NHC Key Laboratory of Myopia Fudan University Shanghai China
- Laboratory of Myopia Chinese Academy of Medical Sciences Shanghai China
- Shanghai Key Laboratory of Visual Impairment and Restoration Fudan University Shanghai China
- State Key Laboratory of Medical Neurobiology, Institutes of Brain Science Fudan University Shanghai China
| | - Jianjiang Xu
- Department of Ophthalmology and Vision Science, Eye and Ear, Nose, Throat Hospital, Shanghai Medical College Fudan University Shanghai China
- NHC Key Laboratory of Myopia Fudan University Shanghai China
- Laboratory of Myopia Chinese Academy of Medical Sciences Shanghai China
- Shanghai Key Laboratory of Visual Impairment and Restoration Fudan University Shanghai China
| | - Jihong Wu
- Department of Ophthalmology and Vision Science, Eye and Ear, Nose, Throat Hospital, Shanghai Medical College Fudan University Shanghai China
- NHC Key Laboratory of Myopia Fudan University Shanghai China
- Laboratory of Myopia Chinese Academy of Medical Sciences Shanghai China
- Shanghai Key Laboratory of Visual Impairment and Restoration Fudan University Shanghai China
| | - Rong Zhang
- Department of Ophthalmology and Vision Science, Eye and Ear, Nose, Throat Hospital, Shanghai Medical College Fudan University Shanghai China
- NHC Key Laboratory of Myopia Fudan University Shanghai China
- Laboratory of Myopia Chinese Academy of Medical Sciences Shanghai China
- Shanghai Key Laboratory of Visual Impairment and Restoration Fudan University Shanghai China
| | - Gang Li
- Department of Ophthalmology and Vision Science, Eye and Ear, Nose, Throat Hospital, Shanghai Medical College Fudan University Shanghai China
- NHC Key Laboratory of Myopia Fudan University Shanghai China
- Laboratory of Myopia Chinese Academy of Medical Sciences Shanghai China
- Shanghai Key Laboratory of Visual Impairment and Restoration Fudan University Shanghai China
| | - Kang Xue
- Department of Ophthalmology and Vision Science, Eye and Ear, Nose, Throat Hospital, Shanghai Medical College Fudan University Shanghai China
- Shanghai Key Laboratory of Visual Impairment and Restoration Fudan University Shanghai China
| | - Xiaoling Zhang
- Department of Orthopedic Surgery Xin Hua Hospital Affiliated to Shanghai Jiaotong University School of Medicine Shanghai China
| | - Shaohong Qian
- Department of Ophthalmology and Vision Science, Eye and Ear, Nose, Throat Hospital, Shanghai Medical College Fudan University Shanghai China
- NHC Key Laboratory of Myopia Fudan University Shanghai China
- Laboratory of Myopia Chinese Academy of Medical Sciences Shanghai China
- Shanghai Key Laboratory of Visual Impairment and Restoration Fudan University Shanghai China
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Guan C, Pease ME, Quillen S, Ling YTT, Li X, Kimball E, Johnson TV, Nguyen TD, Quigley HA. Quantitative Microstructural Analysis of Cellular and Tissue Remodeling in Human Glaucoma Optic Nerve Head. Invest Ophthalmol Vis Sci 2022; 63:18. [PMID: 36269186 PMCID: PMC9617510 DOI: 10.1167/iovs.63.11.18] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 09/23/2022] [Indexed: 12/02/2022] Open
Abstract
Purpose To measure quantitatively changes in lamina cribrosa (LC) cell and connective tissue structure in human glaucoma eyes. Methods We studied 27 glaucoma and 19 age-matched non-glaucoma postmortem eyes. In 25 eyes, LC cross-sections were examined by confocal and multiphoton microscopy to quantify structures identified by anti-glial fibrillary acidic protein (GFAP), phalloidin-labeled F-actin, nuclear 4',6-diamidino-2-phenylindole (DAPI), and by second harmonic generation imaging of LC beams. Additional light and transmission electron microscopy were performed in 21 eyes to confirm features of LC remodeling, including immunolabeling by anti-SOX9 and anti-collagen IV. All glaucoma eyes had detailed clinical histories of open-angle glaucoma status, and degree of axon loss was quantified in retrolaminar optic nerve cross-sections. Results Within LC pores, the proportionate area of both GFAP and F-actin processes was significantly lower in glaucoma eyes than in controls (P = 0.01). Nuclei were rounder (lower median aspect ratio) in glaucoma specimens (P = 0.02). In models assessing degree of glaucoma damage, F-actin process width was significantly wider in glaucoma eyes with more damage (P = 0.024), average LC beam width decreased with worse glaucoma damage (P = 0.042), and nuclear count per square millimeter rose with worse damage (P = 0.019). The greater cell count in LC pores represented 92.3% astrocytes by SOX9 labeling. The results are consistent with replacement of axons in LC pores by basement membrane labeled by anti-collagen IV and in-migrating astrocytes. Conclusions Alteration in LC structure in glaucoma involves migration of astrocytes into axonal bundles, change in astrocyte orientation and processes, production of basement membrane material, and thinning of connective tissue beams.
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Affiliation(s)
- Carolyn Guan
- Wilmer Ophthalmological Institute, School of Medicine, The Johns Hopkins University, Baltimore, Maryland, United States
| | - Mary Ellen Pease
- Wilmer Ophthalmological Institute, School of Medicine, The Johns Hopkins University, Baltimore, Maryland, United States
| | - Sarah Quillen
- Wilmer Ophthalmological Institute, School of Medicine, The Johns Hopkins University, Baltimore, Maryland, United States
| | - Yik Tung Tracy Ling
- Departments of Mechanical Engineering and Materials Science & Engineering, The Johns Hopkins University, Baltimore, Maryland, United States
| | - Ximin Li
- Department of Biostatistics, The Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, Maryland, United States
| | - Elizabeth Kimball
- Wilmer Ophthalmological Institute, School of Medicine, The Johns Hopkins University, Baltimore, Maryland, United States
| | - Thomas V. Johnson
- Wilmer Ophthalmological Institute, School of Medicine, The Johns Hopkins University, Baltimore, Maryland, United States
| | - Thao D. Nguyen
- Wilmer Ophthalmological Institute, School of Medicine, The Johns Hopkins University, Baltimore, Maryland, United States
- Departments of Mechanical Engineering and Materials Science & Engineering, The Johns Hopkins University, Baltimore, Maryland, United States
| | - Harry A. Quigley
- Wilmer Ophthalmological Institute, School of Medicine, The Johns Hopkins University, Baltimore, Maryland, United States
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Wang Y, Cao H. Corneal and Scleral Biomechanics in Ophthalmic Diseases: An Updated Review. MEDICINE IN NOVEL TECHNOLOGY AND DEVICES 2022. [DOI: 10.1016/j.medntd.2022.100140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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8
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Zhang YY, Zhao H, Lin JY, Wu SN, Liu XW, Zhang HD, Shao Y, Yang WF. Artificial Intelligence to Detect Meibomian Gland Dysfunction From in-vivo Laser Confocal Microscopy. Front Med (Lausanne) 2021; 8:774344. [PMID: 34901091 PMCID: PMC8655877 DOI: 10.3389/fmed.2021.774344] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2021] [Accepted: 11/04/2021] [Indexed: 02/05/2023] Open
Abstract
Background: In recent years, deep learning has been widely used in a variety of ophthalmic diseases. As a common ophthalmic disease, meibomian gland dysfunction (MGD) has a unique phenotype in in-vivo laser confocal microscope imaging (VLCMI). The purpose of our study was to investigate a deep learning algorithm to differentiate and classify obstructive MGD (OMGD), atrophic MGD (AMGD) and normal groups. Methods: In this study, a multi-layer deep convolution neural network (CNN) was trained using VLCMI from OMGD, AMGD and healthy subjects as verified by medical experts. The automatic differential diagnosis of OMGD, AMGD and healthy people was tested by comparing its image-based identification of each group with the medical expert diagnosis. The CNN was trained and validated with 4,985 and 1,663 VLCMI images, respectively. By using established enhancement techniques, 1,663 untrained VLCMI images were tested. Results: In this study, we included 2,766 healthy control VLCMIs, 2,744 from OMGD and 2,801 from AMGD. Of the three models, differential diagnostic accuracy of the DenseNet169 CNN was highest at over 97%. The sensitivity and specificity of the DenseNet169 model for OMGD were 88.8 and 95.4%, respectively; and for AMGD 89.4 and 98.4%, respectively. Conclusion: This study described a deep learning algorithm to automatically check and classify VLCMI images of MGD. By optimizing the algorithm, the classifier model displayed excellent accuracy. With further development, this model may become an effective tool for the differential diagnosis of MGD.
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Affiliation(s)
- Ye-Ye Zhang
- Department of Electronic Engineering, School of Science, Hainan University, Haikou, China.,Department of Electronic Engineering, College of Engineering, Shantou University, Shantou, China
| | - Hui Zhao
- Department of Ophthalmology, Shanghai First People's Hospital, Shanghai Jiao Tong University, National Clinical Research Center for Eye Diseases, Shanghai, China
| | - Jin-Yan Lin
- Research Center for Advanced Optics and Photoelectronics, Department of Physics, College of Science, Shantou University, Shantou, China
| | - Shi-Nan Wu
- Jiangxi Centre of National Ophthalmology Clinical Research Center, Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Nanchang, China
| | - Xi-Wang Liu
- Research Center for Advanced Optics and Photoelectronics, Department of Physics, College of Science, Shantou University, Shantou, China.,Department of Mathematics, College of Science, Shantou University, Shantou, China
| | - Hong-Dan Zhang
- Research Center for Advanced Optics and Photoelectronics, Department of Physics, College of Science, Shantou University, Shantou, China.,Department of Mathematics, College of Science, Shantou University, Shantou, China
| | - Yi Shao
- Jiangxi Centre of National Ophthalmology Clinical Research Center, Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Nanchang, China
| | - Wei-Feng Yang
- Department of Electronic Engineering, College of Engineering, Shantou University, Shantou, China.,Research Center for Advanced Optics and Photoelectronics, Department of Physics, College of Science, Shantou University, Shantou, China.,Department of Mathematics, College of Science, Shantou University, Shantou, China
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Brais-Brunet S, Heckel É, Kanniyappan U, Chemtob S, Boudoux C, Joyal JS, Dehaes M. Morphometric and Microstructural Changes During Murine Retinal Development Characterized Using In Vivo Optical Coherence Tomography. Invest Ophthalmol Vis Sci 2021; 62:20. [PMID: 34698774 PMCID: PMC8556565 DOI: 10.1167/iovs.62.13.20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Purpose The purpose of this study was to develop an in vivo optical coherence tomography (OCT) system capable of imaging the developing mouse retina and its associated morphometric and microstructural changes. Methods Thirty-four wild-type mice (129S1/SvlmJ) were anesthetized and imaged between postnatal (P) day 7 and P21. OCT instrumentation was developed to optimize signal intensity and image quality. Semi-automatic segmentation tools were developed to quantify the retinal thickness of the nerve fiber layer (NFL), inner plexiform layer (IPL), inner nuclear layer (INL), and the outer retinal layers (ORL), in addition to the total retina. The retinal maturation was characterized by comparing layer thicknesses between consecutive time points. Results From P7 to P10, the IPL increased significantly, consistent with retinal synaptogenesis. From P10 to P12, the IPL and ORL also increased, which is coherent with synaptic connectivity and photoreceptor maturation. In contrast, during these periods, the INL decreased significantly, consistent with cellular densification and selective apoptotic “pruning” of the tissue during nuclear migration. Thereafter from P12 to P21, the INL continued to thin (significantly from P17 to P21) whereas the other layers remained unchanged. No time-dependent changes were observed in the NFL. Overall, changes in the total retina were attributed to those in the IPL, INL, and ORL. Regions of the retina adjacent to the optic nerve head were thinner than distal regions during maturation. Conclusions Changes in retinal layer thickness are consistent with retinal developmental mechanisms. Accordingly, this report opens new horizons in using our system in the mouse to characterize longitudinally developmental digressions in models of human diseases.
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Affiliation(s)
- Simon Brais-Brunet
- Institute of Biomedical Engineering, University of Montréal, Montréal, Canada.,Research Center, CHU Sainte-Justine, Montréal, Canada
| | - Émilie Heckel
- Research Center, CHU Sainte-Justine, Montréal, Canada.,Department of Pharmacology, University of Montréal, Montréal, Canada
| | - Udayakumar Kanniyappan
- Institute of Biomedical Engineering, University of Montréal, Montréal, Canada.,Research Center, CHU Sainte-Justine, Montréal, Canada
| | - Sylvain Chemtob
- Research Center, CHU Sainte-Justine, Montréal, Canada.,Department of Pharmacology, University of Montréal, Montréal, Canada.,Department of Pediatrics, University of Montréal, Montréal, Canada.,Department of Ophthalmology, University of Montréal, Montréal, Canada
| | - Caroline Boudoux
- Research Center, CHU Sainte-Justine, Montréal, Canada.,Department of Engineering Physics, Polytechnique Montréal, Montréal, Canada
| | - Jean-Sébastien Joyal
- Research Center, CHU Sainte-Justine, Montréal, Canada.,Department of Pharmacology, University of Montréal, Montréal, Canada.,Department of Pediatrics, University of Montréal, Montréal, Canada.,Department of Ophthalmology, University of Montréal, Montréal, Canada
| | - Mathieu Dehaes
- Institute of Biomedical Engineering, University of Montréal, Montréal, Canada.,Research Center, CHU Sainte-Justine, Montréal, Canada.,Department of Radiology, Radio-oncology and Nuclear Medicine, University of Montréal, Montréal, Canada
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Schwaner SA, Perry RN, Kight AM, Winder E, Yang H, Morrison JC, Burgoyne CF, Ross Ethier C. Individual-Specific Modeling of Rat Optic Nerve Head Biomechanics in Glaucoma. J Biomech Eng 2021; 143:041004. [PMID: 33210142 PMCID: PMC7871999 DOI: 10.1115/1.4049157] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 11/11/2020] [Indexed: 02/04/2023]
Abstract
Glaucoma is the second leading cause of blindness worldwide and is characterized by the death of retinal ganglion cells (RGCs), the cells that send vision information to the brain. Their axons exit the eye at the optic nerve head (ONH), the main site of damage in glaucoma. The importance of biomechanics in glaucoma is indicated by the fact that elevated intraocular pressure (IOP) is a causative risk factor for the disease. However, exactly how biomechanical insult leads to RGC death is not understood. Although rat models are widely used to study glaucoma, their ONH biomechanics have not been characterized in depth. Therefore, we aimed to do so through finite element (FE) modeling. Utilizing our previously described method, we constructed and analyzed ONH models with individual-specific geometry in which the sclera was modeled as a matrix reinforced with collagen fibers. We developed eight sets of scleral material parameters based on results from our previous inverse FE study and used them to simulate the effects of elevated IOP in eight model variants of each of seven rat ONHs. Within the optic nerve, highest strains were seen inferiorly, a pattern that was consistent across model geometries and model variants. In addition, changing the collagen fiber direction to be circumferential within the peripapillary sclera resulted in more pronounced decreases in strain than changing scleral stiffness. The results from this study can be used to interpret data from rat glaucoma studies to learn more about how biomechanics affects RGC pathogenesis in glaucoma.
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Affiliation(s)
- Stephen A. Schwaner
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332
| | - Robert N. Perry
- Department of Biomedical Engineering, University of Virginia, Charlottesville, VA 22904
| | - Alison M. Kight
- Department of Bioengineering, Stanford University, Stanford, CA 94305
| | - Emily Winder
- Coulter Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, GA 30332
| | - Hongli Yang
- Optic Nerve Head Research Laboratory, Discoveries in Sight Research Laboratories, Devers Eye Institute, Legacy Health System, Portland, OR 97210
| | - John C. Morrison
- The Kenneth C. Swan Ocular Neurobiology Laboratory, Casey Eye Institute, Oregon Health and Science University, Portland, OR 97239
| | - Claude F. Burgoyne
- Optic Nerve Head Research Laboratory, Discoveries in Sight Research Laboratories, Devers Eye Institute, Legacy Health System, Portland, OR 97210
| | - C. Ross Ethier
- Coulter Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, GA 30332
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Korneva A, Kimball EC, Jefferys JL, Quigley HA, Nguyen TD. Biomechanics of the optic nerve head and peripapillary sclera in a mouse model of glaucoma. J R Soc Interface 2020; 17:20200708. [PMID: 33323053 PMCID: PMC7811579 DOI: 10.1098/rsif.2020.0708] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 11/17/2020] [Indexed: 01/09/2023] Open
Abstract
The deformation of the mouse astrocytic lamina (AL) and adjacent peripapillary sclera (PPS) was measured in response to elevated intraocular pressure. We subjected explanted mouse eyes to inflation testing, comparing control eyes to those 3 days and 6 weeks after induction of ocular hypertension (OHT) via ocular microbead injection. Laser scanning microscopy was used with second harmonic generation to image the collagenous PPS and two-photon fluorescence to image transgenic fluorescent astrocytes in the AL. Digital volume correlation was applied to calculate strains in the PPS and AL. The specimen-averaged strains were biaxial in the AL and PPS, with greater strain overall in the x- than y-direction in the AL and greater strain in the θ- than the r-direction in the PPS. Strains increased after 3-day OHT, with greater strain overall in the 3-day AL than control AL, and greater circumferential strain in the 3-day PPS than control PPS. In the 6-week OHT eyes, AL and PPS strains were similar overall to controls. This experimental glaucoma model demonstrated a dynamic change in the mechanical behaviour of the AL and PPS over time at the site of neuronal injury and remodelling in glaucoma.
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Affiliation(s)
- Arina Korneva
- Glaucoma Center of Excellence, Wilmer Eye Institute, John Hopkins University, Baltimore, MD, USA
| | - Elizabeth C. Kimball
- Glaucoma Center of Excellence, Wilmer Eye Institute, John Hopkins University, Baltimore, MD, USA
| | - Joan L. Jefferys
- Glaucoma Center of Excellence, Wilmer Eye Institute, John Hopkins University, Baltimore, MD, USA
| | - Harry A. Quigley
- Glaucoma Center of Excellence, Wilmer Eye Institute, John Hopkins University, Baltimore, MD, USA
| | - Thao D. Nguyen
- Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, MD 21218, USA
- Department of Ophthalmology, The Johns Hopkins University, Baltimore, MD 21218, USA
- Department of Materials Science, The Johns Hopkins University, Baltimore, MD 21218, USA
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12
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Qiu C, Yao J, Zhang X, Zhang R, Sun X, Qian S. The Dynamic Scleral Extracellular Matrix Alterations in Chronic Ocular Hypertension Model of Rats. Front Physiol 2020; 11:682. [PMID: 32719611 PMCID: PMC7349004 DOI: 10.3389/fphys.2020.00682] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Accepted: 05/26/2020] [Indexed: 11/23/2022] Open
Abstract
Intraocular pressure (IOP) generates stress and strains in the laminar cribrosa and sclera, which may affect the development and progression of glaucoma. Scleral stiffness and material components have changed under elevated IOP. However, the detailed changes of the components of the hypertensive sclera are not well understood. In this study, we aimed to investigate the changes of the main components in the scleral extracellular matrix (ECM), and matrix metalloproteinase 2 (MMP2) and their relationship with time under chronic elevated IOP in Sprague–Dawley rats. An ocular hypertension model was established in the right eyes by anterior chamber injection with 0.3% carbomer solution. The left eye was used as the contralateral control. Immunofluorescent imaging of the tissue frozen sections, Western blot analysis, and quantitative PCR (qPCR) were performed to detect the expressions of type I collagen (COL1), elastin, and MMP2 in the sclera. The ocular hypertension model was successfully established. As compared to the left eyes, the immunofluorescence imaging, Western blot analysis, and qPCR showed that COL1, elastin, and MMP2 were significantly increased in the right eyes at 1 week (all P < 0.05). At 2 weeks, COL1 in the right eyes tended to be lower than that in the left eyes, while elastin and MMP2 were still higher (all P < 0.05) in the right eyes. When the IOP was elevated for 4 weeks, both COL1 and MMP2 were lower than those in the left eyes (all P < 0.05), while elastin between the two eyes was similar (P > 0.05). Under this 4-week hypertensive state, COL1 and elastin were initially elevated at 1 week, and then obviously reduced from 2 to 4 weeks. Consistently, MMP2 was gradually increased, with a peak at 2 weeks, and then decreased at 4 weeks. In conclusion, the chronic elevated IOP induced dynamic scleral ECM alterations in rats in a pressure- and time-dependent manner. MMP2 may play an important role in the balance between ECM synthesis and degradation and could potentially be a novel target for glaucoma intervention.
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Affiliation(s)
- Chen Qiu
- Department of Ophthalmology and Vision Science, Eye and Ear, Nose, Throat Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,NHC Key Laboratory of Myopia, Fudan University, Shanghai, China.,Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China
| | - Jing Yao
- Department of Ophthalmology and Vision Science, Eye and Ear, Nose, Throat Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,NHC Key Laboratory of Myopia, Fudan University, Shanghai, China.,Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China
| | - Xi Zhang
- Department of Ophthalmology, Zhongshan Hospital of Fudan University, Shanghai, China
| | - Rong Zhang
- Department of Ophthalmology and Vision Science, Eye and Ear, Nose, Throat Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,NHC Key Laboratory of Myopia, Fudan University, Shanghai, China.,Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China
| | - Xinghuai Sun
- Department of Ophthalmology and Vision Science, Eye and Ear, Nose, Throat Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,NHC Key Laboratory of Myopia, Fudan University, Shanghai, China.,Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China.,State Key Laboratory of Medical Neurobiology, Institutes of Brain Science, Fudan University, Shanghai, China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University, Shanghai, China
| | - Shaohong Qian
- Department of Ophthalmology and Vision Science, Eye and Ear, Nose, Throat Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,NHC Key Laboratory of Myopia, Fudan University, Shanghai, China.,Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China
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13
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Midgett D, Liu B, Ling YTT, Jefferys JL, Quigley HA, Nguyen TD. The Effects of Glaucoma on the Pressure-Induced Strain Response of the Human Lamina Cribrosa. Invest Ophthalmol Vis Sci 2020; 61:41. [PMID: 32343781 PMCID: PMC7401932 DOI: 10.1167/iovs.61.4.41] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2019] [Accepted: 02/16/2020] [Indexed: 12/14/2022] Open
Abstract
Purpose To measure the ex vivo pressure-induced strain response of the human optic nerve head and analyze for variations with glaucoma diagnosis and optic nerve axon damage. Methods The posterior sclera of 16 eyes from 8 diagnosed glaucoma donors and 10 eyes from 6 donors with no history of glaucoma were inflation tested between 5 and 45 mm Hg. The optic nerve from each donor was examined for degree of axon loss. The posterior volume of the lamina cribrosa (LC) was imaged with second harmonic generation and analyzed using volume correlation to calculate LC strains between 5 and 10 and 5 and 45 mm Hg. Results Eye length and LC area were larger in eyes diagnosed with glaucoma (P ≤ 0.03). Nasal-temporal EXX and circumferential Eθθ strains were lower in the LC of diagnosed glaucoma eyes at 10 mm Hg (P ≤ 0.05) and 45 mm Hg (P ≤ 0.07). EXX was smaller in the LC of glaucoma eyes with <25% axon loss compared with undamaged normal eyes (P = 0.01, 45 mm Hg). In general, the strains were larger in the peripheral than central LC. The ratio of the maximum principal strain Emax in the peripheral to central LC was larger in glaucoma eyes with >25% axon loss than in glaucoma eyes with milder damage (P = 0.004, 10 mm Hg). Conclusions The stiffness of the LC pressure-strain response was greater in diagnosed glaucoma eyes and varied with glaucomatous axon damage. Lower LC strains in glaucoma eyes with milder damage may represent baseline biomechanical behavior that contributes to axon loss, whereas greater LC strain and altered radial LC strain variation in glaucoma eyes with more severe damage may be caused by glaucoma-related remodeling.
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Affiliation(s)
- Dan Midgett
- Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, Maryland, United States
| | - Baiyun Liu
- Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, Maryland, United States
| | - Yik Tung Tracy Ling
- Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, Maryland, United States
| | - Joan L. Jefferys
- Wilmer Ophthalmological Institute, School of Medicine, The Johns Hopkins University, Baltimore, Maryland, United States
| | - Harry A. Quigley
- Wilmer Ophthalmological Institute, School of Medicine, The Johns Hopkins University, Baltimore, Maryland, United States
| | - Thao D. Nguyen
- Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, Maryland, United States
- Department of Materials Science, The Johns Hopkins University, Baltimore, Maryland, United States
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14
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Midgett DE, Jefferys JL, Quigley HA, Nguyen TD. The inflation response of the human lamina cribrosa and sclera: Analysis of deformation and interaction. Acta Biomater 2020; 106:225-241. [PMID: 32044458 PMCID: PMC8340454 DOI: 10.1016/j.actbio.2020.01.049] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Revised: 01/28/2020] [Accepted: 01/30/2020] [Indexed: 11/23/2022]
Abstract
This study investigated the inflation response of the lamina cribrosa (LC) and adjacent peripapillary sclera (PPS) in post-mortem human eyes with no history of glaucoma. The posterior sclera of 13 human eyes from 7 donors was subjected to controlled pressurization between 5-45 mmHg. A laser-scanning microscope (LSM) was used to image the second harmonic generation (SHG) response of collagen and the two-photon fluorescent (TPF) response of elastin within the volume of the LC and PPS at each pressure. Image volumes were analyzed using digital volume correlation (DVC) to calculate the three-dimensional (3D) deformation field between pressures. The LC exhibited larger radial strain, Err, and maximum principal strain, Emax, (p < 0.0001) and greater posterior displacement (p=0.0007) compared to the PPS between 5-45 mmHg, but had similar average circumferential strain, Eθθ, and maximum shear strain, Γmax. The Emax and Γmax were highest near the LC-PPS interface and lowest in the nasal quadrant of both tissues. Larger LC area was associated with smaller Emax in the peripheral LC and larger Emax in the central LC (p ≤ 0.01). The Emax, Γmax, and Eθθ in the inner PPS increased with increasing strain in adjacent LC regions (p ≤ 0.001). Smaller strains in the PPS were associated with a larger difference in the posterior displacement between the PPS and central LC (p < 0.0001 for Emax and Err), indicating that a stiffer pressure-strain response of the PPS is associated with greater posterior bowing of the LC. STATEMENT OF SIGNIFICANCE: Glaucoma causes vision loss through progressive damage of the retinal ganglion axons at the lamina cribrosa (LC), a connective tissue structure that supports the axons as they pass through the eye wall. It is hypothesized that strains caused by intraocular pressure may initiate this damage and that these strains are modulated by the combined deformation of the LC and adjacent peripapillary sclera (PPS). In this study we present a method to measure the pressure-induced 3D displacement and strain field in the LC and PPS simultaneously. Regional strain variation in the LC and PPS was investigated and compared and strains were analyzed for associations with age, LC area, LC strain magnitude, and LC posterior motion relative to the PPS.
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Affiliation(s)
- Dan E Midgett
- Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA.
| | - Joan L Jefferys
- Wilmer Ophthalmological Institute, School of Medicine, The Johns Hopkins University, Baltimore, MD 21287, USA
| | - Harry A Quigley
- Wilmer Ophthalmological Institute, School of Medicine, The Johns Hopkins University, Baltimore, MD 21287, USA
| | - Thao D Nguyen
- Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, MD 21218, USA; Department of Materials Science, The Johns Hopkins University, Baltimore, MD 21218, USA.
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15
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Dai X, Ye S, Chen X, Jiang T, Huang H, Li W, Yu H, Bao J, Chen H. Rodent retinal microcirculation and visual electrophysiology following simulated microgravity. Exp Eye Res 2020; 194:108023. [PMID: 32222454 DOI: 10.1016/j.exer.2020.108023] [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: 10/30/2019] [Revised: 03/20/2020] [Accepted: 03/23/2020] [Indexed: 11/30/2022]
Abstract
How the absence of gravity affects the physiology of human beings is generating global research interest as space exploration, including missions aboard the International Space Station, continues to push boundaries. Here, we examined changes in retinal microcirculation and visual electrophysiology in mice suspended by their tails to simulate the cephalad movement of blood that occurs under microgravity conditions. Tail suspension was performed with a head-down tilt with a recommended angle of 30°. Mice in the control groups were similarly attached to a tether but could maintain a normal position. Morphologically, the 15-day tail-suspended mice showed retinal microvascular dilation, tortuosity, and a relatively long fluorescence retention; however, the average diameter of the major retinal vessels was not notably changed. In addition, optical coherence tomography showed their optic nerve head had an increased diameter. However, the mice could adapt to the change, with microcirculation and the optic nerve head recovering following 30-day tail suspension. Expression of rhodopsin and cone-opsins was not notably changed, and no retinal apoptotic-positive cells were detected between 15- and 30-day tail suspensions. Moreover, the three experimental groups of suspended mice showed normal retinal layers and thickness. Functionally, following 15-day tail suspension, scotopic electroretinograms showed a decline in the oscillatory potentials (OPs), but not in the b wave; simultaneously, the peak time of flash visual evoked potential component N1 was delayed compared to its baseline and the time-matched control. Following 30-day tail suspension, the OPs (O2) amplitude recovered to approximately 97% of its baseline or 86% of the time-matched control level. By simulating cephalad shifting of blood, short-term tail suspension can affect rodent retinal microcirculation, the optic nerve head, and disturb visual electrophysiology. However, the change is reversible with no permanent injury observed in the retina. The mice could adapt to the short-term change of retinal microcirculation, indicating new conditions that could be combined with, or could enhance, simulated microgravity for further studying the impact of short- or long-term outer space conditions on the retina.
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Affiliation(s)
- Xufeng Dai
- School of Ophthalmology and Optometry, The Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, 325027, China
| | - Siming Ye
- New York University Shanghai, Shanghai, 200120, China
| | - Xiaoping Chen
- Laboratory of Human Factors Engineering, China Astronaut Research and Training Center, Beijing, 100094, China
| | - Ting Jiang
- Laboratory of Human Factors Engineering, China Astronaut Research and Training Center, Beijing, 100094, China
| | - Haixiao Huang
- School of Ophthalmology and Optometry, The Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, 325027, China
| | - Wenjiong Li
- Laboratory of Human Factors Engineering, China Astronaut Research and Training Center, Beijing, 100094, China
| | - Hongqiang Yu
- Laboratory of Human Factors Engineering, China Astronaut Research and Training Center, Beijing, 100094, China
| | - Jinhua Bao
- School of Ophthalmology and Optometry, The Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, 325027, China.
| | - Hao Chen
- School of Ophthalmology and Optometry, The Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, 325027, China.
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16
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Boote C, Sigal IA, Grytz R, Hua Y, Nguyen TD, Girard MJA. Scleral structure and biomechanics. Prog Retin Eye Res 2019; 74:100773. [PMID: 31412277 DOI: 10.1016/j.preteyeres.2019.100773] [Citation(s) in RCA: 139] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 08/07/2019] [Accepted: 08/08/2019] [Indexed: 12/18/2022]
Abstract
As the eye's main load-bearing connective tissue, the sclera is centrally important to vision. In addition to cooperatively maintaining refractive status with the cornea, the sclera must also provide stable mechanical support to vulnerable internal ocular structures such as the retina and optic nerve head. Moreover, it must achieve this under complex, dynamic loading conditions imposed by eye movements and fluid pressures. Recent years have seen significant advances in our knowledge of scleral biomechanics, its modulation with ageing and disease, and their relationship to the hierarchical structure of the collagen-rich scleral extracellular matrix (ECM) and its resident cells. This review focuses on notable recent structural and biomechanical studies, setting their findings in the context of the wider scleral literature. It reviews recent progress in the development of scattering and bioimaging methods to resolve scleral ECM structure at multiple scales. In vivo and ex vivo experimental methods to characterise scleral biomechanics are explored, along with computational techniques that combine structural and biomechanical data to simulate ocular behaviour and extract tissue material properties. Studies into alterations of scleral structure and biomechanics in myopia and glaucoma are presented, and their results reconciled with associated findings on changes in the ageing eye. Finally, new developments in scleral surgery and emerging minimally invasive therapies are highlighted that could offer new hope in the fight against escalating scleral-related vision disorder worldwide.
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Affiliation(s)
- Craig Boote
- Structural Biophysics Research Group, School of Optometry & Vision Sciences, Cardiff University, UK; Ophthalmic Engineering & Innovation Laboratory (OEIL), Department of Biomedical Engineering, National University of Singapore, Singapore; Newcastle Research & Innovation Institute Singapore (NewRIIS), Singapore.
| | - Ian A Sigal
- Laboratory of Ocular Biomechanics, Department of Ophthalmology, University of Pittsburgh, USA
| | - Rafael Grytz
- Department of Ophthalmology & Visual Sciences, University of Alabama at Birmingham, USA
| | - Yi Hua
- Laboratory of Ocular Biomechanics, Department of Ophthalmology, University of Pittsburgh, USA
| | - Thao D Nguyen
- Department of Mechanical Engineering, Johns Hopkins University, USA
| | - Michael J A Girard
- Ophthalmic Engineering & Innovation Laboratory (OEIL), Department of Biomedical Engineering, National University of Singapore, Singapore; Singapore Eye Research Institute (SERI), Singapore National Eye Centre, Singapore
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