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Islam MR, Ji F, Bansal M, Hua Y, Sigal IA. Fibrous finite element modeling of the optic nerve head region. Acta Biomater 2024; 175:123-137. [PMID: 38147935 DOI: 10.1016/j.actbio.2023.12.034] [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: 05/17/2023] [Revised: 12/06/2023] [Accepted: 12/20/2023] [Indexed: 12/28/2023]
Abstract
The optic nerve head (ONH) region at the posterior pole of the eye is supported by a fibrous structure of collagen fiber bundles. Discerning how the fibrous structure determines the region biomechanics is crucial to understand normal physiology, and the roles of biomechanics on vision loss. The fiber bundles within the ONH structure exhibit complex three-dimensional (3D) organization and continuity across the various tissue components. Computational models of the ONH, however, usually represent collagen fibers in a homogenized fashion without accounting for their continuity across tissues, fibers interacting with each other and other fiber-specific effects in a fibrous structure. We present a fibrous finite element (FFE) model of the ONH that incorporates discrete collagen fiber bundles and their histology-based 3D organization to study ONH biomechanics as a fibrous structure. The FFE model was constructed using polarized light microscopy data of porcine ONH cryosections, representing individual fiber bundles in the sclera, dura and pia maters with beam elements and canal tissues as continuum structures. The FFE model mimics the histological in-plane orientation and width distributions of collagen bundles as well as their continuity across different tissues. Modeling the fiber bundles as linear materials, the FFE model predicts the nonlinear ONH response observed in an inflation experiment from the literature. The model also captures important microstructural mechanisms including fiber interactions and long-range strain transmission among bundles that have not been considered before. The FFE model presented here advances our understanding of the role of fibrous collagen structure in the ONH biomechanics. STATEMENT OF SIGNIFICANCE: The microstructure and mechanics of the optic nerve head (ONH) are central to ocular physiology. Histologically, the ONH region exhibits a complex continuous fibrous structure of collagen bundles. Understanding the role of the fibrous collagen structure on ONH biomechanics requires high-fidelity computational models previously unavailable. We present a computational model of the ONH that incorporates histology-based fibrous collagen structure derived from polarized light microscopy images. The model predictions agree with experiments in the literature, and provide insight into important microstructural mechanisms of fibrous tissue biomechanics, such as long-range strain transmission along fiber bundles. Our model can be used to study the microstructural basis of biomechanical damage and the effects of collagen remodeling in glaucoma.
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Affiliation(s)
- Mohammad R Islam
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh PA, USA; Department of Mechanical Engineering, University of Texas Rio Grande Valley, Edinburg TX, USA
| | - Fengting Ji
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh PA, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh PA, USA
| | - Manik Bansal
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh PA, USA
| | - Yi Hua
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh PA, USA; Department of Biomedical Engineering, University of Mississippi, MS, USA
| | - Ian A Sigal
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh PA, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh PA, USA.
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Kristiansen M, Holmlund P, Lindén C, Eklund A, Jóhannesson G. Optic Nerve Subarachnoid Space Posture Dependency - An MRI Study in Subjects With Normal Tension Glaucoma and Healthy Controls. Invest Ophthalmol Vis Sci 2023; 64:20. [PMID: 38099734 PMCID: PMC10729838 DOI: 10.1167/iovs.64.15.20] [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: 06/22/2023] [Accepted: 10/29/2023] [Indexed: 12/18/2023] Open
Abstract
Purpose The purpose of this study was to examine the differences of optic nerve subarachnoid space (ONSAS) volume in patients with normal tension glaucoma (NTG) and healthy controls in different body positions. Methods Eight patients with NTG and seven healthy controls underwent magnetic resonance imaging (MRI) examinations in head up tilt (HUT) +11 degrees and head down tilt (HDT) -5 degrees positions according to a randomized protocol determining the starting position. The ONSAS volume in both body positions was measured and compared between the two groups. The results were analyzed using a generalized linear model. Results Between HDT and HUT, the postural ONSAS volume change was dependent on starting position (P < 0.001) and group (P = 0.003, NTG versus healthy). A subgroup analysis of those that were randomized to HUT examination first, coming directly from an upright position, showed that the patients with NTG had significantly larger positional ONSAS volume changes compared to the healthy controls; 121 ± 22 µL vs. 65 ± 37 µL (P = 0.049). Analysis of the ONSAS volume distribution showed different profiles for patients with NTG and healthy controls. Conclusions There was a significant difference in ONSAS volume change between patients with NTG and healthy subjects when subjected to posture changes, specifically when going from upright to head-down posture. This indicates that patients with NTG had been exposed to a lower ONSAS pressure when they came from the upright posture, which suggests an increased translaminar pressure difference in upright position. This may support the theory that NTG has a dysfunction in an occlusion mechanism of the optic nerve sheath that could cause abnormally negative ONSAS pressures in upright posture.
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Affiliation(s)
- Martin Kristiansen
- Department of Clinical Sciences, Ophthalmology, Umeå University, Umeå, Sweden
| | - Petter Holmlund
- Department of Radiation Sciences, Radiation Physics, Biomedical Engineering, Umeå University, Umeå, Sweden
| | - Christina Lindén
- Department of Clinical Sciences, Ophthalmology, Umeå University, Umeå, Sweden
| | - Anders Eklund
- Department of Radiation Sciences, Radiation Physics, Biomedical Engineering, Umeå University, Umeå, Sweden
- Umeå Centre for Functional Brain Imaging, Umeå University, Umeå, Sweden
| | - Gauti Jóhannesson
- Department of Clinical Sciences, Ophthalmology, Umeå University, Umeå, Sweden
- Wallenberg Center for Molecular Medicine, Umeå University, Umeå, Sweden
- Department of Ophthalmology, University of Iceland, Reykjavik, Iceland
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Zhu Z, Waxman S, Wang B, Wallace J, Schmitt SE, Tyler-Kabara E, Ishikawa H, Schuman JS, Smith MA, Wollstein G, Sigal IA. In vivo Modulation of Intraocular and Intracranial Pressures Causes Nonlinear and Non-monotonic Deformations of the Lamina Cribrosa and Scleral Canal. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.29.526113. [PMID: 36778255 PMCID: PMC9915473 DOI: 10.1101/2023.01.29.526113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Purpose To evaluate changes in monkey optic nerve head (ONH) morphology under acutely controlled intraocular pressure (IOP) and intracranial pressure (ICP). Methods Seven ONHs from six monkeys were imaged via optical coherence tomography while IOP and ICP were maintained at one of 16 conditions. These conditions were defined by 4 levels for each pressure: low, baseline, high and very high. Images were processed to determine scleral canal area, aspect ratio, and planarity and anterior lamina cribrosa (ALC) shape index and curvature. Linear mixed effect models were utilized to investigate the effects of IOP, ICP and their interactions on ONH morphological features. The IOP-ICP interaction model was compared with one based on translaminar pressure difference (TLPD). Results We observed complex, eye-specific, non-linear patterns of ONH morphological changes with changes in IOP and ICP. For all ONH morphological features, linear mixed effects models demonstrated significant interactions between IOP and ICP that were unaccounted for by TLPD. Interactions indicate that the effects of IOP and ICP depend on the other pressure. The IOP-ICP interaction model was a higher quality predictor of ONH features than a TLPD model. Conclusions In vivo modulation of IOP and ICP causes nonlinear and non-monotonic changes in monkey ONH morphology that depend on both pressures and is not accounted for by a simplistic TLPD. These results support and extend prior findings. Translational Relevance A better understanding of ICP's influence on the effects of IOP can help inform the highly variable presentations of glaucoma and effective treatment strategies.
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Affiliation(s)
- Ziyi Zhu
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
| | - Susannah Waxman
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Bo Wang
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
- Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Jacob Wallace
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Samantha E. Schmitt
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Elizabeth Tyler-Kabara
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Neurosurgery, University of Texas-Austin, Austin, TX, USA
| | - Hiroshi Ishikawa
- Department of Ophthalmology, Casey Eye Institute, Oregon Health and Science University, Portland, OR, USA
- Department of Medical Informatics and Clinical Epidemiology (DMICE), Oregon Health & Science University, Portland, OR, USA
| | - Joel S. Schuman
- Department of Ophthalmology, NYU School of Medicine, New York, NY, USA
| | - Matthew A. Smith
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
- Neuroscience Institute, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Gadi Wollstein
- Department of Ophthalmology, NYU School of Medicine, New York, NY, USA
| | - Ian A. Sigal
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
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Association between Optic Nerve Sheath Diameter and Lamina Cribrosa Morphology in Normal-Tension Glaucoma. J Clin Med 2023; 12:jcm12010360. [PMID: 36615160 PMCID: PMC9821661 DOI: 10.3390/jcm12010360] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 12/28/2022] [Accepted: 12/29/2022] [Indexed: 01/04/2023] Open
Abstract
(1) Background: To compare optic nerve sheath diameter (ONSD) in normal-tension glaucoma (NTG) and healthy eyes and to investigate the association between ONSD and lamina cribrosa (LC) morphology. (2) Methods: This cross-sectional study included 69 NTG eyes and 69 healthy eyes matched for age, axial length, and intraocular pressure. The LC curvature index (LCCI) was measured from horizontal Cirrus HD-OCT B-scan images from five uniformly divided positions vertically of the optic nerve. The average LCCI was defined as the mean of the measurements at these five locations. ONSD was measured as the width of the optic nerve sheath at the site perpendicular 3 mm behind the posterior globe. LCCI and ONSD were compared in eyes with NTG and healthy eyes. The clinical factors that could affect LCCI were analyzed. (3) Results: NTG eyes had significantly smaller mean ONSD (4.55 ± 0.69 mm vs. 4.97 ± 0.58 mm, p < 0.001) and larger average LCCI (11.61 ± 1.43 vs. 7.58 ± 0.90, p < 0.001) than matched healthy control eyes. LCCI was significantly correlated with smaller ONSD, higher intraocular pressure, thinner global retinal nerve fiber thickness, and worse visual field loss in all subjects (all Ps ≤ 0.022). (4) Conclusions: NTG eyes had smaller ONSD and greater LCCI than healthy control eyes. In addition, a negative correlation was observed between ONSD and LCCI. These findings suggest that cerebrospinal fluid pressure, which ONSD indirectly predicts, may affect LC configuration. Changes in the retrolaminar compartment may play a role in glaucoma pathogenesis.
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Chuangsuwanich T, Tun TA, Braeu FA, Wang X, Chin ZY, Panda SK, Buist M, Strouthidis N, Perera S, Nongpiur M, Aung T, Girard MJA. Differing Associations between Optic Nerve Head Strains and Visual Field Loss in Patients with Normal- and High-Tension Glaucoma. Ophthalmology 2023; 130:99-110. [PMID: 35964710 DOI: 10.1016/j.ophtha.2022.08.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 07/13/2022] [Accepted: 08/04/2022] [Indexed: 01/06/2023] Open
Abstract
PURPOSE To study the associations between optic nerve head (ONH) strains under intraocular pressure (IOP) elevation with retinal sensitivity in patients with glaucoma. DESIGN Clinic-based cross-sectional study. PARTICIPANTS Two hundred twenty-nine patients with primary open-angle glaucoma (subdivided into 115 patients with high-tension glaucoma [HTG] and 114 patients with normal-tension glaucoma [NTG]). METHODS For 1 eye of each patient, we imaged the ONH using spectral-domain OCT under the following conditions: (1) primary gaze and (2) primary gaze with acute IOP elevation (to approximately 35 mmHg) achieved through ophthalmodynamometry. A 3-dimensional strain-mapping algorithm was applied to quantify IOP-induced ONH tissue strain (i.e., deformation) in each ONH. Strains in the prelaminar tissue (PLT), the retina, the choroid, the sclera, and the lamina cribrosa (LC) were associated (using linear regression) with measures of retinal sensitivity from the 24-2 Humphrey visual field test (Carl Zeiss Meditec). This was performed globally, then locally according to a previously published regionalization scheme. MAIN OUTCOME MEASURES Associations between ONH strains and values of retinal sensitivity from visual field testing. RESULTS For patients with HTG, we found (1) significant negative linear associations between ONH strains and retinal sensitivity (P < 0.001; on average, a 1% increase in ONH strains corresponded to a decrease in retinal sensitivity of 1.1 decibels [dB]), (2) that high-strain regions colocalized with anatomically mapped regions of high visual field loss, and (3) that the strongest negative associations were observed in the superior region and in the PLT. In contrast, for patients with NTG, no significant associations between strains and retinal sensitivity were observed except in the superotemporal region of the LC. CONCLUSIONS We found significant negative associations between IOP-induced ONH strains and retinal sensitivity in a relatively large glaucoma cohort. Specifically, patients with HTG who experienced higher ONH strains were more likely to exhibit lower retinal sensitivities. Interestingly, this trend in general was less pronounced in patients with NTG, which could suggest a distinct pathophysiologic relationship between the two glaucoma subtypes.
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Affiliation(s)
- Thanadet Chuangsuwanich
- Ophthalmic Engineering & Innovation Laboratory, Singapore Eye Research Institute, Singapore National Eye Center, Singapore, Republic of Singapore; Department of Biomedical Engineering, National University of Singapore, Singapore, Republic of Singapore.
| | - Tin A Tun
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Republic of Singapore; Duke-NUS Medical School, Singapore, Republic of Singapore
| | - Fabian A Braeu
- Ophthalmic Engineering & Innovation Laboratory, Singapore Eye Research Institute, Singapore National Eye Center, Singapore, Republic of Singapore; Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Republic of Singapore
| | - Xiaofei Wang
- Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, School of Engineering Medicine, Beihang University, Beijing, China
| | - Zhi Yun Chin
- Ophthalmic Engineering & Innovation Laboratory, Singapore Eye Research Institute, Singapore National Eye Center, Singapore, Republic of Singapore; Department of Biomedical Engineering, National University of Singapore, Singapore, Republic of Singapore
| | - Satish Kumar Panda
- Ophthalmic Engineering & Innovation Laboratory, Singapore Eye Research Institute, Singapore National Eye Center, Singapore, Republic of Singapore; Department of Biomedical Engineering, National University of Singapore, Singapore, Republic of Singapore
| | - Martin Buist
- Department of Biomedical Engineering, National University of Singapore, Singapore, Republic of Singapore
| | - Nicholas Strouthidis
- National Institute of Health Research, Biomedical Sciences Centre, Moorfields Eye Hospital and UCL Institute of Ophthalmology, London, United Kingdom
| | - Shamira Perera
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Republic of Singapore
| | - Monisha Nongpiur
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Republic of Singapore; Duke-NUS Medical School, Singapore, Republic of Singapore
| | - Tin Aung
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Republic of Singapore; Duke-NUS Medical School, Singapore, Republic of Singapore
| | - Michaël J A Girard
- Ophthalmic Engineering & Innovation Laboratory, Singapore Eye Research Institute, Singapore National Eye Center, Singapore, Republic of Singapore; Duke-NUS Medical School, Singapore, Republic of Singapore; Institute for Molecular and Clinical Ophthalmology, Basel, Switzerland.
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Wei J, Hua Y, Yang B, Wang B, Schmitt SE, Wang B, Lucy KA, Ishikawa H, Schuman JS, Smith MA, Wollstein G, Sigal IA. Comparing Acute IOP-Induced Lamina Cribrosa Deformations Premortem and Postmortem. Transl Vis Sci Technol 2022; 11:1. [DOI: 10.1167/tvst.11.12.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Affiliation(s)
- Junchao Wei
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Yi Hua
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Bin Yang
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Engineering, Duquesne University, Pittsburgh, PA, USA
| | - Bo Wang
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
- Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Samantha E. Schmitt
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
- Neuroscience Institute, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Bingrui Wang
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Katie A. Lucy
- Department of Ophthalmology, NYU Langone Health, NYU Grossman School of Medicine, New York, NY, USA
| | - Hiroshi Ishikawa
- Department of Ophthalmology, NYU Langone Health, NYU Grossman School of Medicine, New York, NY, USA
- Department of Ophthalmology, Casey Eye Institute, Oregon Health & Science University, Portland, OR, USA
- Department of Medical Informatics and Clinical Epidemiology, Oregon Health & Science University, Portland, OR, USA
| | - Joel S. Schuman
- Department of Ophthalmology, NYU Langone Health, NYU Grossman School of Medicine, New York, NY, USA
- Department of Biomedical Engineering and Electrical and Computer Engineering, New York University Tandon School of Engineering, Brooklyn, NY, USA
- Neuroscience Institute, NYU Langone Health, New York, NY, USA
| | - Matthew A. Smith
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
- Neuroscience Institute, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Gadi Wollstein
- Department of Ophthalmology, NYU Langone Health, NYU Grossman School of Medicine, New York, NY, USA
| | - Ian A. Sigal
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
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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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Peng M, Curry SM, Liu Y, Lohawala H, Sharma G, Sharma TP. The ex vivo human translaminar autonomous system to study spaceflight associated neuro-ocular syndrome pathogenesis. NPJ Microgravity 2022; 8:44. [PMID: 36307487 DOI: 10.1038/s41526-022-00232-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 10/12/2022] [Indexed: 11/10/2022] Open
Abstract
Spaceflight-Associated Neuro-ocular Syndrome (SANS) is a significant unexplained adverse reaction to long-duration spaceflight. We employ an ex vivo translaminar autonomous system (TAS) to recreate a human ocular ground-based spaceflight analogue model to study SANS pathogenesis. To recapitulate the human SANS conditions, human ocular posterior segments are cultured in the TAS model for 14 days. Translaminar pressure differentials are generated by simulating various flow rates within intracranial pressure (ICP) and intraocular (IOP) chambers to maintain hydrostatic pressures of ICP: IOP (12:16, 15:16, 12:21, 21:16 mmHg). In addition, optic nerves are mechanically kinked by 6- and 10-degree tilt inserts for the ICP: IOP;15:16 mmHg pressure paradigm. The TAS model successfully maintains various pressure differentials for all experimental groups over 14 days. Post culture, we determine inflammatory and extracellular component expression changes within posterior segments. To further characterize the SANS pathogenesis, axonal transport capacity, optic nerve degeneration and retinal functional are measured. Identifiable pathogenic alterations are observed in posterior segments by morphologic, apoptotic, and inflammatory changes including transport and functional deficits under various simulated SANS conditions. Here we report our TAS model provides a unique preclinical application system to mimic SANS pathology and a viable therapeutic testing device for countermeasures.
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Affiliation(s)
- Michael Peng
- Eugene and Marilyn Glick Eye Institute, Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA
| | - Stacy M Curry
- North Texas Eye Research Institute, Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX, 76107, USA
| | - Yang Liu
- North Texas Eye Research Institute, Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX, 76107, USA
| | | | - Gaurav Sharma
- Software Engineer Consultant, Indianapolis, IN, 46074, USA
| | - Tasneem P Sharma
- Eugene and Marilyn Glick Eye Institute, Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA. .,Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA. .,Stark Neurosciences Research Institute, Indianapolis, IN, 46202, USA.
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9
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Karimi A, Razaghi R, Rahmati SM, Girkin CA, Downs JC. Relative Contributions of Intraocular and Cerebrospinal Fluid Pressures to the Biomechanics of the Lamina Cribrosa and Laminar Neural Tissues. Invest Ophthalmol Vis Sci 2022; 63:14. [PMID: 36255364 PMCID: PMC9587471 DOI: 10.1167/iovs.63.11.14] [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: 05/13/2022] [Accepted: 09/27/2022] [Indexed: 12/02/2022] Open
Abstract
Purpose The laminar region of the optic nerve head (ONH), thought to be the site of damage to the retinal ganglion cell axons in glaucoma, is continuously loaded on its anterior and posterior surfaces by dynamic intraocular pressure (IOP) and orbital cerebrospinal fluid pressure (CSFP), respectively. Thus, translaminar pressure (TLP; TLP = IOP-CSFP) has been proposed as a glaucoma risk factor. Methods Three eye-specific finite element models of the posterior human eye were constructed, including full 3D microstructures of the load-bearing lamina cribrosa (LC) with interspersed laminar neural tissues (NTs), and heterogeneous, anisotropic, hyperelastic material formulations for the surrounding peripapillary sclera and adjacent pia. ONH biomechanical responses were simulated using three combinations of IOP and CSFP loadings consistent with posture change from sitting to supine. Results Results show that tensile, compressive, and shear stresses and strains in the ONH were higher in the supine position compared to the sitting position (P < 0.05). In addition, LC beams bear three to five times more TLP-driven stress than interspersed laminar NT, whereas laminar NT exhibit three to five times greater strain than supporting LC (P < 0.05). Compared with CSFP, IOP drove approximately four times greater stress and strain in the LC, NT, and peripapillary sclera, normalized per mm Hg pressure change. In addition, IOP drove approximately three-fold greater scleral canal expansion and anterior-posterior laminar deformation than CSFP per mm Hg (P < 0.05). Conclusions Whereas TLP has been hypothesized to play a prominent role in ONH biomechanics, the IOP and CSFP effects are not equivalent, as IOP-driven stress, strain, and deformation play a more dominant role than CSFP effects.
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Affiliation(s)
- Alireza Karimi
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Reza Razaghi
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | | | - Christopher A. Girkin
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - J. Crawford Downs
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, Alabama, United States
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10
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Hua Y, Lu Y, Walker J, Lee PY, Tian Q, McDonald H, Pallares P, Ji F, Brazile BL, Yang B, Voorhees AP, Sigal IA. Eye-specific 3D modeling of factors influencing oxygen concentration in the lamina cribrosa. Exp Eye Res 2022; 220:109105. [PMID: 35568202 PMCID: PMC11007759 DOI: 10.1016/j.exer.2022.109105] [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: 12/21/2021] [Revised: 04/06/2022] [Accepted: 04/28/2022] [Indexed: 11/29/2022]
Abstract
Our goal was to identify the factors with the strongest influence on the minimum lamina cribrosa (LC) oxygen concentration as potentially indicative of conditions increasing hypoxia risk. Because direct measurement of LC hemodynamics and oxygenation is not yet possible, we developed 3D eye-specific LC vasculature models. The vasculature of a normal monkey eye was perfusion-labeled post-mortem. Serial cryosections through the optic nerve head were imaged using fluorescence and polarized light microscopy to visualize the vasculature and collagen, respectively. The vasculature within a 450 μm-thick region containing the LC - identified from the collagen, was segmented, skeletonized, and meshed for simulations. Using Monte Carlo sampling, 200 vascular network models were generated with varying vessel diameter, neural tissue oxygen consumption rate, inflow hematocrit, and blood pressures (arteriole, venule, anterior boundary, and posterior boundary). Factors were varied over ranges of baseline ±20% with uniform probability. For each model we first obtained the blood flow, and from this the neural tissue oxygen concentration. ANOVA was used to identify the factors with the strongest influence on the minimum (10th percentile) oxygen concentration in the LC. The three most influential factors were, in ranked order, vessel diameter, neural tissue oxygen consumption rate, and arteriole pressure. There was a strong interaction between vessel diameter and arteriole pressure whereby the impact of one factor was larger when the other factor was small. Our results show that, for the eye analyzed, conditions that reduce vessel diameter, such as vessel compression due to elevated intraocular pressure or gaze-induced tissue deformation, may particularly contribute to decreased LC oxygen concentration. More eyes must be analyzed before generalizing.
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Affiliation(s)
- Yi Hua
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States
| | - Yuankai Lu
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States
| | - Jason Walker
- Department of Biological Science, University of Pittsburgh, Pittsburgh, PA, United States
| | - Po-Yi Lee
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States
| | - Qi Tian
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States
| | - Haiden McDonald
- Department of Biological Science, University of Pittsburgh, Pittsburgh, PA, United States
| | - Pedro Pallares
- Department of Biological Science, University of Pittsburgh, Pittsburgh, PA, United States
| | - Fengting Ji
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States
| | - Bryn L Brazile
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States
| | - Bin Yang
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States; Department of Engineering, Rangos School of Health Sciences, Duquesne University, Pittsburgh, PA, United States
| | - Andrew P Voorhees
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States
| | - Ian A Sigal
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States.
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11
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Feola AJ, Girkin CA, Ethier CR, Samuels BC. A Potential Role of Acute Choroidal Expansion in Nonarteritic Anterior Ischemic Optic Neuropathy. Invest Ophthalmol Vis Sci 2022; 63:23. [PMID: 35481840 PMCID: PMC9055550 DOI: 10.1167/iovs.63.4.23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose Nonarteritic anterior ischemic optic neuropathy (NAION) has been associated with a thickened choroid at the optic nerve head (ONH). Here, we use computational modeling to better understand how choroidal expansion and choroidal geometry influence tissue deformation within the ONH relative to intraocular pressure (IOP) and intracranial pressure (ICP) effects. Methods Using a model of the posterior eye that included the sclera, peripapillary sclera, annular ring, pia mater, dura mater, neural tissues, Bruch's membrane, choroid, and lamina cribrosa, we examined how varying material properties of ocular tissues influenced ONH deformations under physiological and supra-physiological, or “pathological,” conditions. We considered choroidal expansion (c. 35 µL of expansion), elevated IOP (30 mm Hg), and elevated ICP (20 mm Hg), and calculated peak strains in the ONH relative to a baseline condition representing an individual in the upright position. Results Supra-physiological choroidal expansion had the largest impact on strains in the prelaminar neural tissue. In addition, compared to a tapered choroid, a “blunt” choroid insertion at the ONH resulted in higher strains. Elevated IOP and ICP caused the highest strains within the lamina cribrosa and retrolaminar neural tissue, respectively. Conclusions Acute choroidal expansion caused large deformations of the ONH and these deformations were impacted by choroid geometry. These results are consistent with the concept that compartment syndrome due to the choroid geometry and/or expansion at the ONH contributes to NAION. Prolonged deformations due to supra-physiological loading may induce a mechanobiological response or ischemia, highlighting the potential impact of choroidal expansion on biomechanical strains in the ONH.
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Affiliation(s)
- Andrew J Feola
- Center for Visual and Neurocognitive Rehabilitation, Atlanta VA Medical Center, Atlanta, Georgia, United States.,Department of Ophthalmology, Emory Eye Center, Emory University School of Medicine, Atlanta, Georgia, United States.,Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, GA, United States
| | - Christopher A Girkin
- Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - C Ross Ethier
- Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, GA, United States
| | - Brian C Samuels
- Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama, United States
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12
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Cho KH, Takahashi A, Yamamoto M, Hirouchi H, Taniguchi S, Ogawa Y, Murakami G, Abe SI. Optic nerve-associated connective tissue structures revisited: a histological study using human fetuses and adult cadavers. Anat Rec (Hoboken) 2022; 305:3516-3531. [PMID: 35358354 DOI: 10.1002/ar.24925] [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: 12/20/2021] [Revised: 03/03/2022] [Accepted: 03/08/2022] [Indexed: 11/10/2022]
Abstract
Unlike the usual peripheral nerve, the optic nerve accompanies a thick "dural sheath," a thin "sheath of pia mater" (SPM), and multiple "septa," which divides the nerve fibers into fascicles. We collected specimens from 25 adult cadavers and 15 fetuses and revisited the histological architecture of the optic and oculomotor nerves. In the optic chiasma, the meningeal layer of the dura joins the pia to form a thick SPM, and the periosteum of the sphenoid is continuous with the dural sheath at the orbital exit of the bony optic canal. The septa appeared as a cluster of irregularly arrayed fibrous plates in the intracranial course near the chiasma. Thus, the septa were not derived from either the SPM or the dural sheath. In the orbit, the central artery of the retina accompanies collagenous fibers from the dural sheath and the SPM to provide the vascular sheath in the optic nerve. These connective tissue configurations were the same between adult and fetal specimens. At the optic disk, the dural sheath and SPM merged with the sclera, whereas the septa appeared to end at the lamina cribrosa. However, in fetuses without lamina cribrosa, the septa extend into the nerve fiber layer of the retina. The SPM and septa showed strong elastin immunoreactivity, in contrast to the absence of reactivity in the sheaths of the oculomotor nerve. Each S100 protein-positive Schwann sheath of the oculomotor nerve was surrounded by collagenous endoneurium. Glial fibrillary acidic protein-positive astrocytes showed a linear arrangement along the septa. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Kwang Ho Cho
- Department of Neurology, Wonkwang University School of Medicine and Hospital, Institute of Wonkwang Medical Science, 895, Muwang-ro, Iksan-si, Jeollabuk-do, Republic of Korea
| | | | | | | | | | - Yudai Ogawa
- Department of Histology and Developmental Biology, Tokyo Dental College, Tokyo, Japan
| | - Gen Murakami
- Department of Anatomy, Tokyo Dental College, Tokyo, Japan.,Division of Internal Medicine, Cupid Clinic, Iwamizawa, Japan
| | - Shin-Ichi Abe
- Department of Anatomy, Tokyo Dental College, Tokyo, Japan
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13
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Kedar S, Tong J, Bader J, Havens S, Fan S, Thorell W, Nelson C, Gu L, High R, Gulati V, Ghate D. Effects of Acute Intracranial Pressure Changes on Optic Nerve Head Morphology in Humans and Pig Model. Curr Eye Res 2021; 47:304-311. [PMID: 34894934 DOI: 10.1080/02713683.2021.1952604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
PURPOSE The lamina cribrosa (LC) is a layer of fenestrated connective tissue tethered to the posterior sclera across the scleral canal in the optic nerve head (ONH). It is located at the interface of intracranial and intraocular compartments and is exposed to intraocular pressure (IOP) anteriorly and intracranial pressure (ICP) or Cerebrospinal fluid (CSF) pressure (CSFP) posteriorly. We hypothesize that the pressure difference across LC will determine LC position and meridional diameter of scleral canal (also called Bruch's membrane opening diameter; BMOD). METHODS We enrolled 19 human subjects undergoing a medically necessary lumbar puncture (LP) to lower CSFP and 6 anesthetized pigs, whose ICP was increased in 5 mm Hg increments using a lumbar catheter. We imaged ONH using optical coherence tomography and measured IOP and CSFP/ICP at baseline and after each intervention. Radial tomographic ONH scans were analyzed by two independent graders using ImageJ, an open-source software. The following ONH morphological parameters were obtained: BMOD, anterior LC depth and retinal thickness. We modeled effects of acute CSFP/ICP changes on ONH morphological parameters using ANOVA (human study) and generalized linear model (pig study). RESULTS For 19 human subjects, CSFP ranged from 5 to 42 mm Hg before LP and 2 to 19.4 mm Hg after LP. For the six pigs, baseline ICP ranged from 1.5 to 9 mm Hg and maximum stable ICP ranged from 18 to 40 mm Hg. Our models showed that acute CSFP/ICP changes had no significant effect on ONH morphological parameters in both humans and pigs. CONCLUSION We conclude that ONH does not show measurable morphological changes in response to acute changes of CSFP/ICP. Proposed mechanisms include compensatory and opposing changes in IOP and CSFP/ICP and nonlinear or nonmonotonic effects of IOP and CSFP/ICP across LC.
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Affiliation(s)
- Sachin Kedar
- Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE, USA.,Department of Neurological Sciences, University of Nebraska Medical Center, Omaha, NE, USA
| | - Junfei Tong
- Department of Mechanical Engineering, University of Nebraska, Lincoln, NE, USA
| | - John Bader
- Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE, USA
| | - Shane Havens
- Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE, USA
| | - Shan Fan
- Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE, USA
| | - William Thorell
- Department of Neurosurgery, University of Nebraska Medical Center, Omaha, NE, USA
| | - Carl Nelson
- Department of Mechanical Engineering, University of Nebraska, Lincoln, NE, USA
| | - Linxia Gu
- Department of Mechanical Engineering, University of Nebraska, Lincoln, NE, USA.,Department of Biomedical and Chemical Engineering and Sciences, Florida Institute of Technology, Melbourne, FL, USA
| | - Robin High
- College of Public Health, University of Nebraska Medical Center, Omaha, NE, USA
| | - Vikas Gulati
- Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE, USA
| | - Deepta Ghate
- Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE, USA
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14
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Zhu Z, Waxman S, Wang B, Wallace J, Schmitt SE, Tyler-Kabara E, Ishikawa H, Schuman JS, Smith MA, Wollstein G, Sigal IA. Interplay between intraocular and intracranial pressure effects on the optic nerve head in vivo. Exp Eye Res 2021; 213:108809. [PMID: 34736887 DOI: 10.1016/j.exer.2021.108809] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 10/19/2021] [Accepted: 10/25/2021] [Indexed: 12/19/2022]
Abstract
Intracranial pressure (ICP) has been proposed to play an important role in the sensitivity to intraocular pressure (IOP) and susceptibility to glaucoma. However, the in vivo effects of simultaneous, controlled, acute variations in ICP and IOP have not been directly measured. We quantified the deformations of the anterior lamina cribrosa (ALC) and scleral canal at Bruch's membrane opening (BMO) under acute elevation of IOP and/or ICP. Four eyes of three adult monkeys were imaged in vivo with OCT under four pressure conditions: IOP and ICP either at baseline or elevated. The BMO and ALC were reconstructed from manual delineations. From these, we determined canal area at the BMO (BMO area), BMO aspect ratio and planarity, and ALC median depth relative to the BMO plane. To better account for the pressure effects on the imaging, we also measured ALC visibility as a percent of the BMO area. Further, ALC depths were analyzed only in regions where the ALC was visible in all pressure conditions. Bootstrap sampling was used to obtain mean estimates and confidence intervals, which were then used to test for significant effects of IOP and ICP, independently and in interaction. Response to pressure manipulation was highly individualized between eyes, with significant changes detected in a majority of the parameters. Significant interactions between ICP and IOP occurred in all measures, except ALC visibility. On average, ICP elevation expanded BMO area by 0.17 mm2 at baseline IOP, and contracted BMO area by 0.02 mm2 at high IOP. ICP elevation decreased ALC depth by 10 μm at baseline IOP, but increased depth by 7 μm at high IOP. ALC visibility decreased as ICP increased, both at baseline (-10%) and high IOP (-17%). IOP elevation expanded BMO area by 0.04 mm2 at baseline ICP, and contracted BMO area by 0.09 mm2 at high ICP. On average, IOP elevation caused the ALC to displace 3.3 μm anteriorly at baseline ICP, and 22 μm posteriorly at high ICP. ALC visibility improved as IOP increased, both at baseline (5%) and high ICP (8%). In summary, changing IOP or ICP significantly deformed both the scleral canal and the lamina of the monkey ONH, regardless of the other pressure level. There were significant interactions between the effects of IOP and those of ICP on LC depth, BMO area, aspect ratio and planarity. On most eyes, elevating both pressures by the same amount did not cancel out the effects. Altogether our results show that ICP affects sensitivity to IOP, and thus that it can potentially also affect susceptibility to glaucoma.
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Affiliation(s)
- Ziyi Zhu
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
| | - Susannah Waxman
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Bo Wang
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA; Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Jacob Wallace
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Samantha E Schmitt
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA; Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Elizabeth Tyler-Kabara
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, PA, USA; Department of Neurosurgery, University of Texas-Austin, Austin, TX, USA
| | - Hiroshi Ishikawa
- Department of Ophthalmology, NYU School of Medicine, New York, NY, USA
| | - Joel S Schuman
- Department of Ophthalmology, NYU School of Medicine, New York, NY, USA
| | - Matthew A Smith
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA; Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Gadi Wollstein
- Department of Ophthalmology, NYU School of Medicine, New York, NY, USA
| | - Ian A Sigal
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA.
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15
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Material properties and effect of preconditioning of human sclera, optic nerve, and optic nerve sheath. Biomech Model Mechanobiol 2021; 20:1353-1363. [PMID: 33877503 PMCID: PMC8298341 DOI: 10.1007/s10237-021-01448-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 03/06/2021] [Indexed: 02/03/2023]
Abstract
The optic nerve (ON) is a recently recognized tractional load on the eye during larger horizontal eye rotations. In order to understand the mechanical behavior of the eye during adduction, it is necessary to characterize material properties of the sclera, ON, and in particular its sheath. We performed tensile loading of specimens taken from fresh postmortem human eyes to characterize the range of variation in their biomechanical properties and determine the effect of preconditioning. We fitted reduced polynomial hyperelastic models to represent the nonlinear tensile behavior of the anterior, equatorial, posterior, and peripapillary sclera, as well as the ON and its sheath. For comparison, we analyzed tangent moduli in low and high strain regions to represent stiffness. Scleral stiffness generally decreased from anterior to posterior ocular regions. The ON had the lowest tangent modulus, but was surrounded by a much stiffer sheath. The low-strain hyperelastic behaviors of adjacent anatomical regions of the ON, ON sheath, and posterior sclera were similar as appropriate to avoid discontinuities at their boundaries. Regional stiffnesses within individual eyes were moderately correlated, implying that mechanical properties in one region of an eye do not reliably reflect properties of another region of that eye, and that potentially pathological combinations could occur in an eye if regional properties are discrepant. Preconditioning modestly stiffened ocular tissues, except peripapillary sclera that softened. The nonlinear mechanical behavior of posterior ocular tissues permits their stresses to match closely at low strains, although progressively increasing strain causes particularly great stress in the peripapillary region.
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16
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Kesserwani H. Space Flight-Associated Neuroocular Syndrome, Idiopathic Intracranial Hypertension, and Pseudotumor Cerebri: Phenotypic Descriptions, Pathogenesis, and Hydrodynamics. Cureus 2021; 13:e14103. [PMID: 33907644 PMCID: PMC8067672 DOI: 10.7759/cureus.14103] [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] [Accepted: 03/25/2021] [Indexed: 11/08/2022] Open
Abstract
Recent data from astronauts who have returned to Earth from a long-duration space flight have unequivocally distinguished spaceflight-associated neuro-ocular syndrome (SANS) from idiopathic intracranial hypertension (IIH) and pseudotumor cerebri (PTC). We review the semiology and pathogenesis of these three entities, noting that optic disc edema is what unites them, and this where the similarities between SANS and IIH/PTC end. We distinguish between PTC and IIH and between SANS and IIH/PTC and review the medical and surgical therapy of IIH/PTC. The key to understanding the phenomenon of optic disc edema is the geometry of the optic nerve sheath, which is a simulacrum of an inverted Venturi tube. This allows us to theoretically study the hydrodynamics of the optic nerve sheath by applying simple physical laws, including the Venturi effect, Poiseuille's law, and Reynold's number, and we speculate on nature's design and the correlation of form and function in understanding how cerebrospinal fluid (CSF) circulates in the optic nerve sheath as it approaches the optic nerve head. Recent spectacular data on the histology of the blood nerve-barrier of the optic nerve disc and the glymphatic system of the optic nerve sheath will also help us understand the development of optic disc edema due to the microgravity-induced cephalad shift of CSF in SANS. We will explore the role of the sodium/potassium adenosine triphosphatase (ATPase) pump on choroid plexus epithelial cells and the aquaporin-4 water receptors located on astrocyte end-feet and their complex interactions with the tetracyclines, mineralocorticoids, and therapeutic agents with carbonic anhydrase activity. We also adumbrate the complex interactions between obesity, vitamin A, and 11-beta-hydroxysteroid dehydrogenase and how the aquaporin-4 receptor relates to these interactions.
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17
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Wang X, Tun TA, Nongpiur ME, Htoon HM, Tham YC, Strouthidis NG, Aung T, Cheng CY, Girard MJ. Peripapillary sclera exhibits a v-shaped configuration that is more pronounced in glaucoma eyes. Br J Ophthalmol 2020; 106:491-496. [PMID: 33334817 DOI: 10.1136/bjophthalmol-2020-317900] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 11/02/2020] [Accepted: 11/19/2020] [Indexed: 12/16/2022]
Abstract
AIMS To compare the shape of the anterior surface of the peripapillary sclera (PPS) between glaucoma and healthy subjects. METHODS 88 primary open angle glaucoma (POAG), 98 primary angle closure glaucoma (PACG) and 372 age-matched and gender-matched healthy controls were recruited in this study. The optic nerve head of one randomly selected eye of each subject was imaged with spectral domain optical coherence tomography. The shape of the PPS was measured through an angle defined between a line parallel to the nasal anterior PPS boundary and one parallel to the temporal side. A negative value indicated that the PPS followed an inverted v-shaped configuration (peak pointing towards the vitreous), whereas a positive value indicated that it followed a v-shaped configuration. RESULTS The mean PPS angle in normal controls (4.56±5.99°) was significantly smaller than that in POAG (6.60±6.37°, p=0.011) and PACG (7.90±6.87°, p<0.001). The v-shaped PPS was significantly associated with older age (β=1.79, p<0.001), poorer best-corrected visual acuity (β=3.31, p=0.047), central corneal thickness (β=-0.28, p=0.001), peripapillary choroidal thickness (β=-0.21, p<0.001) and presence of POAG (β=1.94, p<0.009) and PACG (β=2.96, p<0.001). The v-shaped configuration of the PPS significantly increased by 1.46° (p=0.001) in healthy controls for every 10-year increase in age, but not in glaucoma groups. CONCLUSIONS The v-shaped configuration of the PPS was more pronounced in glaucoma eyes than in healthy eyes. This posterior bowing of the PPS may have an impact on the biomechanical environment of the optic nerve head.
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Affiliation(s)
- Xiaofei Wang
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Centre for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Tin A Tun
- Ophthalmic Engineering & Innovation Laboratory, Singapore Eye Research Institute, Singapore.,Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
| | - Monisha Esther Nongpiur
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore.,Duke-NUS Medical School, Singapore
| | - Hla M Htoon
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
| | - Yih Chung Tham
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
| | - Nicholas G Strouthidis
- Moorfields Eye Hospital NHS Foundation Trust, London, UK.,Discipline of Clinical Ophthalmology and Eye Health, University of Sydney, Sydney, New South Wales, Australia
| | - Tin Aung
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore.,Duke-NUS Medical School, Singapore.,Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Ching-Yu Cheng
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
| | - Michael Ja Girard
- Ophthalmic Engineering & Innovation Laboratory, Singapore Eye Research Institute, Singapore .,Duke-NUS Medical School, Singapore
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18
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LIU YUSHU, MA LIPING, GAO WEI, LIU ZHICHENG, WANG SHOUXIN, LIU LIU, GUO XUEQIAN, QIAN XIUQING, LI LIN. THE INFERENCE OF THE CHANGES OF AXONAL TRANSPORT OF OPTIC NERVE BY DEFORMATIONS OF LAMINA CRIBROSA. J MECH MED BIOL 2020. [DOI: 10.1142/s0219519420400278] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Understanding the relationship between the changes in the axonal transport of the optic nerve (ON) and lamina cribrosa (LC) deformation will be helpful to estimate the degree of axonal transport block by measuring the LC deformation in vivo. First, the changes in the axonal transport of the ON were studied using an acute high intraocular pressure (IOP) model, which was established by perfusing saline water into the anterior chamber of cats. The IOP of cat was unilaterally elevated to and maintained at 30, 40, and 50[Formula: see text]mmHg. The axonal transport of the ON was examined by confocal laser scanning microscope. Then the deformations and stress distributions of the LC and ON were calculated using a three-dimensional finite element model of the LC microstructure including ON. The results showed axonal transport changes of ON increased with elevation of the IOPs. While Young’s modulus of the LC and ON were assumed as 0.1[Formula: see text]MPa and 0.03[Formula: see text]MPa, the numerical simulation results showed that LC had displacements of 0.02, 0.03, and 0.04[Formula: see text]mm backward at the IOPs of 30, 40, and 50[Formula: see text]mmHg, respectively. The calculated compressive strain applied to the ON were 0.0425, 0.0567, and 0.0709 under 30, 40, and 50[Formula: see text]mmHg IOP, respectively. The results of strain and stress analysis of LC and ON showed that the deformation of LC would compress the ON. The axonal transport abnormalities could be inferred by measuring the LC deformation in vivo.
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Affiliation(s)
- YUSHU LIU
- Beijing Key Laboratory of Fundamental, Research on Biomechanics in Clinical Application, Capital Medical University, Beijing 100069, P. R. China
- School of Biomedical Engineering, Capital Medical University, Beijing 100069, P. R. China
| | - LIPING MA
- School of Biomedical Engineering, Capital Medical University, Beijing 100069, P. R. China
| | - WEI GAO
- Handan Central Hospital, Handan, Hebei 056001, P. R. China
| | - ZHICHENG LIU
- School of Biomedical Engineering, Capital Medical University, Beijing 100069, P. R. China
| | - SHOUXIN WANG
- School of Biomedical Engineering, Capital Medical University, Beijing 100069, P. R. China
| | - LIU LIU
- School of Biomedical Engineering, Capital Medical University, Beijing 100069, P. R. China
| | - XUEQIAN GUO
- School of Biomedical Engineering, Capital Medical University, Beijing 100069, P. R. China
| | - XIUQING QIAN
- Beijing Key Laboratory of Fundamental, Research on Biomechanics in Clinical Application, Capital Medical University, Beijing 100069, P. R. China
- School of Biomedical Engineering, Capital Medical University, Beijing 100069, P. R. China
| | - LIN LI
- Beijing Key Laboratory of Fundamental, Research on Biomechanics in Clinical Application, Capital Medical University, Beijing 100069, P. R. China
- School of Biomedical Engineering, Capital Medical University, Beijing 100069, P. R. China
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19
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Jasien JV, Fazio MA, Samuels BC, Johnston JM, Downs JC. Quantification of Translaminar Pressure Gradient (TLPG) With Continuous Wireless Telemetry in Nonhuman Primates (NHPs). Transl Vis Sci Technol 2020; 9:18. [PMID: 33240571 PMCID: PMC7671865 DOI: 10.1167/tvst.9.12.18] [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: 07/27/2020] [Accepted: 10/10/2020] [Indexed: 12/21/2022] Open
Abstract
Purpose Recent retrospective clinical and animal studies suggest that cerebrospinal fluid pressure (CSFP) is important in glaucoma pathogenesis. Intraocular pressure (IOP) and CSFP are the driving components of translaminar pressure (TLP = IOP - CSFP), which acts across the lamina cribrosa (LC) thickness to create the translaminar pressure gradient (TLPG = TLP/LC thickness). Methods We developed an implantable wireless telemetry system based on a small piezoelectric sensor with low temporal drift. IOP, measured in the anterior chamber, and intracranial pressure (ICP), measured in the brain parenchyma (as a surrogate for CSFP) were measured at 200 Hz in three male rhesus macaques (nonhuman primates, NHPs) on a 10% duty cycle (15 seconds of every 150-second period). Three-dimensional LC thickness was autosegmented as the mean thickness of the visible hyperreflective band in 48 radial spectral-domain optical coherence tomography b-scans centered on the optic nerve head. Results Results indicated the rank order of IOP, ICP, TLP, and TLPG for waking, sleeping, and 24-hour periods averaged across all days. NHP 150110 had the highest IOP and ICP in all periods; however, it had the lowest TLPG in all periods due to its relatively thick LC. The other two NHPs showed similar shifts in the rank order of possible glaucoma risk factors. Conclusions IOP is the only modifiable and readily measurable pressure-based risk factor for glaucoma. However, other potential risk factors such as ICP, TLP, and TLPG, as well as their rank-order patterns, differed compared to IOP across subjects, demonstrating that a comprehensive view of relevant risk factors is warranted. Translational Relevance Future studies should consider including CSFP, TLP, and TLPG in addition to IOP as potential risk factors when assessing eye-specific glaucoma susceptibility.
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Affiliation(s)
- Jessica V Jasien
- Vision Science Graduate Program, School of Optometry, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Massimo A Fazio
- Department of Ophthalmology and Visual Sciences, School of Medicine, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Brian C Samuels
- Department of Ophthalmology and Visual Sciences, School of Medicine, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - James M Johnston
- Department of Neurosurgery, School of Medicine, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - J Crawford Downs
- Department of Ophthalmology and Visual Sciences, School of Medicine, The University of Alabama at Birmingham, Birmingham, AL, USA
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Ma Y, Kwok S, Sun J, Pan X, Pavlatos E, Clayson K, Hazen N, Liu J. IOP-induced regional displacements in the optic nerve head and correlation with peripapillary sclera thickness. Exp Eye Res 2020; 200:108202. [PMID: 32861767 PMCID: PMC7655654 DOI: 10.1016/j.exer.2020.108202] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 08/13/2020] [Accepted: 08/25/2020] [Indexed: 12/30/2022]
Abstract
Mechanical insult induced by intraocular pressure (IOP) is likely a driving force in the disease process of glaucoma. This study aimed to evaluate regional displacements in human optic nerve head (ONH) and peripapillary tissue (PPT) in response to acute IOP elevations, and their correlations with morphological characteristics of the posterior eye. Cross-sectional (2D) images of the ONH and PPT in 14 globes of 14 human donors were acquired with high-frequency ultrasound during whole globe inflation from 5 to 30 mm Hg. High-frequency ultrasound has a spatial resolution of tens of micrometers and is capable of imaging through the ONH and PPT thickness. Tissue displacements were calculated using a correlation-based speckle tracking algorithm for a dense matrix of kernels covering the 2D imaging plane. The ONH was manually segmented in the ultrasound B-mode images acquired at 5 mmHg based on echogenicity. The lamina cribrosa (LC) boundaries were visible in eight of the fourteen eyes and the LC region was segmented using a semi-automated superpixel-based method. The ONH had larger radial displacement than the PPT in all tested eyes and the difference increased with increasing IOP. A significant negative correlation was found between ONH-PPT displacement difference and PPT thickness (p < 0.05), while no significant correlations were found between ONH-PPT displacement difference and other morphological parameters including PPT radius of curvature, scleral canal size, LC thickness and anterior LC surface depth. Within the ONH, the radial displacement decreased in the region anterior to and across LC but not in the region posterior to LC. Finite element models using simplified geometry and material properties confirmed the role of LC in reducing the overall ONH radial displacements, but did not predict the displacement gradient change observed experimentally. These results suggested that a thinner PPT may be associated with a larger relative posterior motion of the ONH with respect to the surrounding PPT and the LC may play a major role in preventing excessive posterior displacement of ONH during acute IOP elevations.
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Affiliation(s)
- Yanhui Ma
- Department of Biomedical Engineering, Ohio State University, Columbus, OH, USA
| | - Sunny Kwok
- Department of Biomedical Engineering, Ohio State University, Columbus, OH, USA
| | - Jiajun Sun
- Department of Biomedical Engineering, Ohio State University, Columbus, OH, USA
| | - Xueliang Pan
- Department of Biomedical Informatics, Ohio State University, Columbus, OH, USA
| | - Elias Pavlatos
- Department of Biomedical Engineering, Ohio State University, Columbus, OH, USA
| | - Keyton Clayson
- Department of Biomedical Engineering, Ohio State University, Columbus, OH, USA; Biophysics Interdisciplinary Group, Ohio State University, Columbus, OH, USA
| | - Nicholas Hazen
- Department of Biomedical Engineering, Ohio State University, Columbus, OH, USA; Biophysics Interdisciplinary Group, Ohio State University, Columbus, OH, USA
| | - Jun Liu
- Department of Biomedical Engineering, Ohio State University, Columbus, OH, USA; Biophysics Interdisciplinary Group, Ohio State University, Columbus, OH, USA; Department of Ophthalmology and Visual Science, Ohio State University, Columbus, OH, USA.
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Quantitative magnetic resonance image assessment of the optic nerve and surrounding sheath after spaceflight. NPJ Microgravity 2020; 6:30. [PMID: 33083526 PMCID: PMC7545196 DOI: 10.1038/s41526-020-00119-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Accepted: 09/10/2020] [Indexed: 11/25/2022] Open
Abstract
A subset of long-duration spaceflight astronauts have experienced ophthalmic abnormalities, collectively termed spaceflight-associated neuro-ocular syndrome (SANS). Little is understood about the pathophysiology of SANS; however, microgravity-induced alterations in intracranial pressure (ICP) due to headward fluid shifts is the primary hypothesized contributor. In particular, potential changes in optic nerve (ON) tortuosity and ON sheath (ONS) distension may indicate altered cerebrospinal fluid dynamics during weightlessness. The present longitudinal study aims to provide a quantitative analysis of ON and ONS cross-sectional areas, and ON deviation, an indication of tortuosity, before and after spaceflight. Ten astronauts undergoing ~6-month missions on the International Space Station (ISS) underwent high-resolution magnetic resonance imaging (MRI) preflight and at five recovery time points extending to 1 year after return from the ISS. The mean changes in ON deviation, ON cross-sectional area, and ONS cross-sectional area immediately post flight were −0.14 mm (95% CI: −0.36 to 0.08, Bonferroni-adjusted P = 1.00), 0.13 mm2 (95% CI −0.66 to 0.91, Bonferroni-adjusted P = 1.00), and −0.22 mm2 (95% CI: −1.78 to 1.34, Bonferroni-adjusted P = 1.00), respectively, and remained consistent during the recovery period. Terrestrially, ONS distension is associated with increased ICP; therefore, these results suggest that, on average, ICP was not pathologically elevated immediately after spaceflight. However, a subject diagnosed with optic disc edema (Frisen Grade 1, right eye) displayed increased ONS area post flight, although this increase is relatively small compared to clinical populations with increased ICP. Advanced quantitative MRI-based assessment of the ON and ONS could help our understanding of SANS and the role of ICP.
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Chuangsuwanich T, Hung PT, Wang X, Liang LH, Schmetterer L, Boote C, Girard MJA. Morphometric, Hemodynamic, and Biomechanical Factors Influencing Blood Flow and Oxygen Concentration in the Human Lamina Cribrosa. Invest Ophthalmol Vis Sci 2020; 61:3. [PMID: 32271886 PMCID: PMC7401712 DOI: 10.1167/iovs.61.4.3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Purpose We developed a combined biomechanical and hemodynamic model of the human eye to estimate blood flow and oxygen concentration within the lamina cribrosa (LC) and rank the factors that influence LC oxygen concentration. Methods We generated 5000 finite-element eye models with detailed microcapillary networks of the LC and computed the oxygen concentration of the lamina retinal ganglion cell axons. For each model, we varied the intraocular pressure (IOP) from 10 mm Hg to 55 mm Hg in 5-mm Hg increments, the cerebrospinal fluid pressure (13 ± 2 mm Hg), cup depth (0.2 ± 0.1 mm), scleral stiffness (±20% of the mean values), LC stiffness (0.41 ± 0.2 MPa), LC radius (1.2 ± 0.12 mm), average LC pore size (5400 ± 2400 µm2), the microcapillary arrangement (radial, isotropic, or circumferential), and perfusion pressure (50 ± 9 mm Hg). Blood flow was assumed to originate from the LC periphery and drain via the central retinal vein. Finally, we performed linear regressions to rank the influence of each factor on the LC tissue oxygen concentration. Results LC radius and perfusion pressure were the most important factors in influencing the oxygen concentration of the LC. IOP was another important parameter, and eyes with higher IOP had higher compressive strain and slightly lower oxygen concentration. In general, superior–inferior regions of the LC had significantly lower oxygen concentration than the nasal–temporal regions, resulting in an hourglass pattern of oxygen deficiency. Conclusions To the best of our knowledge, this study is the first to implement a comprehensive hemodynamical model of the eye that accounts for the biomechanical forces and morphological parameters of the LC. The results provide further insight into the possible relationship of biomechanical and vascular pathways leading to ischemia-induced optic neuropathy.
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Shen G, Link SS, Tao X, Frankfort BJ. Modeling a potential SANS countermeasure by experimental manipulation of the translaminar pressure difference in mice. NPJ Microgravity 2020; 6:19. [PMID: 32821777 PMCID: PMC7395713 DOI: 10.1038/s41526-020-00109-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Accepted: 07/06/2020] [Indexed: 12/23/2022] Open
Abstract
The spaceflight-associated neuro-ocular syndrome (SANS), which may present after prolonged exposure to microgravity, is thought to occur due to elevated intracranial pressure (ICP). Intracranial pressure interacts with intraocular pressure (IOP) to define the translaminar pressure difference (TLPD; IOP-ICP). We combined inducible models of ICP and IOP elevation in mice to interrogate the relationships among ICP, IOP, and TLPD, and to determine if IOP elevation could mitigate the phenotypes typically caused by elevated ICP and thereby serve as a countermeasure for SANS. Ten C57BL6J mice of both genders underwent experimental elevation of ICP via infusion of artificial cerebrospinal fluid into the subarachnoid space. One eye also underwent experimental elevation of IOP using the bead injection model. Intraocular pressure and ICP were monitored for 2 weeks. Optokinetic-based contrast sensitivity was measured at baseline and after 2 weeks, and post-mortem studies of optic nerve and retina anatomy were performed. Photopic contrast sensitivity was reduced more in IOP elevated than control eyes. Scotopic contrast sensitivity was reduced similarly in IOP elevated and control eyes. However, the pattern of scotopic vision loss was not uniform in IOP elevated eyes; there was minimal loss in eyes that most closely approximated the normal TLPD. Optic nerve axon loss, increased optic nerve disorganization, and retinal ganglion cell loss all occurred similarly between IOP elevated and control eyes. Elevation of IOP in eyes with elevated ICP may counterbalance some effects on vision loss but exacerbate others, suggesting complex relationships among IOP, ICP, and TLPD.
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Affiliation(s)
- Guofu Shen
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX USA
| | - Schuyler S. Link
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX USA
| | - Xiaofeng Tao
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX USA
| | - Benjamin J. Frankfort
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX USA
- Department of Neuroscience, Baylor College of Medicine, Houston, TX USA
- Center for Space Medicine, Baylor College of Medicine, Houston, TX USA
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Ma Y, Pavlatos E, Clayson K, Kwok S, Pan X, Liu J. Three-Dimensional Inflation Response of Porcine Optic Nerve Head Using High-Frequency Ultrasound Elastography. J Biomech Eng 2020; 142:051013. [PMID: 31750882 PMCID: PMC7104765 DOI: 10.1115/1.4045503] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 10/30/2019] [Indexed: 12/29/2022]
Abstract
Characterization of the biomechanical behavior of the optic nerve head (ONH) in response to intraocular pressure (IOP) elevation is important for understanding glaucoma susceptibility. In this study, we aimed to develop and validate a three-dimensional (3D) ultrasound elastographic technique to obtain mapping and visualization of the 3D distributive displacements and strains of the ONH and surrounding peripapillary tissue (PPT) during whole globe inflation from 15 to 30 mmHg. 3D scans of the posterior eye around the ONH were acquired through full tissue thickness with a high-frequency ultrasound system (50 MHz). A 3D cross-correlation-based speckle-tracking algorithm was used to compute tissue displacements at ∼30,000 kernels distributed within the region of interest (ROI), and the components of the strain tensors were calculated at each kernel by using least square estimation of the displacement gradients. The accuracy of displacement calculation was evaluated using simulated rigid-body translation on ultrasound radiofrequency (RF) data obtained from a porcine posterior eye. The accuracy of strain calculation was evaluated using finite element (FE) models. Three porcine eyes were tested showing that ONH deformation was heterogeneous with localized high strains. Substantial radial (i.e., through-thickness) compression was observed in the anterior ONH and out-of-plane (i.e., perpendicular to the surface of the shell) shear was shown to concentrate in the vicinity of ONH/PPT border. These preliminary results demonstrated the feasibility of this technique to achieve comprehensive 3D evaluation of the mechanical responses of the posterior eye, which may provide mechanistic insights into the regional susceptibility in glaucoma.
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Affiliation(s)
- Yanhui Ma
- Department of Biomedical Engineering, Ohio State
University, 1080 Carmack Road,
Columbus, OH 43210
e-mail:
| | - Elias Pavlatos
- Department of Biomedical Engineering, Ohio State
University, 1080 Carmack Road,
Columbus, OH 43210
e-mail:
| | - Keyton Clayson
- Department of Biomedical Engineering, Ohio State
University, 1080 Carmack Road,
Columbus, OH 43210
e-mail:
| | - Sunny Kwok
- Department of Biomedical Engineering, Ohio State
University, 1080 Carmack Road,
Columbus, OH 43210
e-mail:
| | - Xueliang Pan
- Department of Biomedical Informatics, Ohio State
University, 1800 Cannon Drive,
Columbus, OH 43210
e-mail:
| | - Jun Liu
- Department of Biomedical Engineering, Ohio State
University, 1080 Carmack Road,
Columbus, OH 43210
e-mail:
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Jasien JV, Samuels BC, Johnston JM, Downs JC. Diurnal Cycle of Translaminar Pressure in Nonhuman Primates Quantified With Continuous Wireless Telemetry. Invest Ophthalmol Vis Sci 2020; 61:37. [PMID: 32097479 PMCID: PMC7329631 DOI: 10.1167/iovs.61.2.37] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Purpose Recent retrospective clinical studies and animal experiments have suggested that cerebrospinal fluid pressure (CSFP) is important in glaucoma pathogenesis. Intraocular pressure (IOP) and CSFP are the driving components of the translaminar pressure (TLP), which directly effects the optic nerve head. This study measured the diurnal cycle of TLP using continuous wireless telemetry in nonhuman primates (NHPs), a common animal model of glaucoma. Methods We have developed an implantable wireless telemetry system based on a small piezoelectric pressure transducer with low drift. Unilateral IOP was measured in the anterior chamber of the eye, and intracranial pressure (ICP, a surrogate measure of CSFP) was measured in the brain parenchyma in four awake, behaving NHPs for periods of 22 to 281 days. IOP and ICP telemetry transducers were calibrated with direct pressure measurements in the eye (every 2 weeks) and brain (monthly). TLP was quantified in real time as IOP-ICP, and hourly means of IOP, ICP, and TLP were analyzed. Results Results show that mean ICP is significantly higher by an average of 4.8 ± 0.8 mmHg during sleeping hours in NHPs (P < 0.01). IOP showed a small but significant nocturnal elevation in two of four animals despite NHPs sleeping upright (P < 0.05). TLP was significantly lower during sleep (7.1 ± 0.6 mmHg; P < 0.01) than when the animals were awake and active (11.0 ± 0.9 mmHg), driven primarily by the large increase in ICP during sleep. Conclusions The 56% increase in TLP during waking hours in NHPs matches the increase in TLP due to postural change from supine to upright reported previously in humans.
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Custom Optical Coherence Tomography Parameters for Distinguishing Papilledema from Pseudopapilledema. Optom Vis Sci 2020; 96:599-608. [PMID: 31318797 DOI: 10.1097/opx.0000000000001408] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
SIGNIFICANCE Causes of papilledema can be life-threatening; however, distinguishing papilledema from pseudopapilledema is often challenging. The conventional optical coherence tomography (OCT) scan for assessing the optic nerve often fails to detect mild papilledema. Our study suggests that parameters derived from volumetric OCT scans can provide additional useful information for detecting papilledema. PURPOSE Optical coherence tomography analysis of the optic nerve commonly measures retinal nerve fiber layer thickness (RNFLT) along a 1.73-mm-radius scan path. This conventional scan, however, often fails to detect mild papilledema. The purpose of this study was to evaluate additional OCT-derived measures of the optic nerve head (ONH) and peripapillary retina for differentiating papilledema (all grades and mild) from pseudopapilledema. METHODS Cirrus OCT ONH volume scans were acquired from 21 papilledema (15 mild papilledema), 27 pseudopapilledema, and 42 control subjects. Raw scan data were exported, and total retinal thickness within Bruch's membrane opening (BMO) plus RNFLT and total retinal thickness at the following eccentricities were calculated using custom algorithms: BMO to 250, 250 to 500, 500 to 1000, and 1000 to 1500 μm. Minimum rim width was calculated, and BMO height was measured from a 4-mm Bruch's membrane reference plane centered on the BMO. RESULTS Retinal nerve fiber layer thickness from BMO to 250 μm, minimum rim width, and BMO height had significantly greater areas under the receiver operating characteristic curve than did conventional RNFLT for differentiating mild papilledema from pseudopapilledema (P < .0001) and greater sensitivities at 95% specificity. Using cutoff values at 95% specificity, custom parameters detected 10 mild papilledema patients, and conventional RNFLT detected only 1. Bruch's membrane opening heights above the reference plane were observed in papilledema only, although many papilledema cases had a neutral or negative BMO height. CONCLUSIONS Using OCT volumetric data, additional parameters describing peripapillary tissue thickness, neuroretinal rim thickness, and ONH position can be calculated and provide valuable measures for differentiating mild papilledema from pseudopapilledema.
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The effects of negative periocular pressure on intraocular pressure. Exp Eye Res 2020; 191:107928. [PMID: 31926968 DOI: 10.1016/j.exer.2020.107928] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 12/04/2019] [Accepted: 01/08/2020] [Indexed: 11/22/2022]
Abstract
Glaucoma is a major cause of blindness, and IOP reduction remains the only clinically-validated therapy. In this study, we analyze a novel IOP-lowering strategy that uses a modest negative pressure (vacuum) applied locally to the periorbital region by a pair of goggles with each lens individually connected to a programmable pump. Motivated by clinical data showing an IOP reduction, we used an existing validated lumped-parameter model of the eye to understand the putative mechanism of this treatment. The model considers aqueous humor dynamics, episcleral venous pressure, and changes in ocular blood volume to describe how IOP changes with time in response to an external perturbation. We find that clinical data are qualitatively and quantitatively consistent with model predictions if we include two primary mechanisms in the model: first, negative pressure application causes a relatively rapid increase in globe volume accompanied by increased blood volume in the eye. Second, negative pressure application reduces episcleral venous pressure, causing a slower adjustment of IOP due to altered aqueous humor dynamics. These results provide testable hypotheses that hopefully will lead to a fuller experimentally-driven understanding of how negative periocular pressure influences IOP. Evaluating the long-term effects of such treatments on glaucoma patients requires further clinical study.
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28
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Liu KC, Fleischman D, Lee AG, Killer HE, Chen JJ, Bhatti MT. Current concepts of cerebrospinal fluid dynamics and the translaminar cribrosa pressure gradient: a paradigm of optic disk disease. Surv Ophthalmol 2020; 65:48-66. [DOI: 10.1016/j.survophthal.2019.08.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 08/07/2019] [Accepted: 08/16/2019] [Indexed: 12/11/2022]
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The Translaminar Pressure Gradient: Papilledema After Trabeculectomy Treated With Optic Nerve Sheath Fenestration. J Glaucoma 2019; 27:e154-e157. [PMID: 29979338 DOI: 10.1097/ijg.0000000000001021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
INTRODUCTION Trans-lamina cribrosa pressure has been postulated to be a contributor in the development of a glaucomatous optic nerve versus optic nerve edema, depending on the pressure gradient. Uncertainty remains in the therapeutic outcome of adjusting this gradient. CASE REPORT We discuss a unique case of idiopathic intracranial hypertension presenting as asymmetric optic disc edema following trabeculectomy. It was treated via optic nerve fenestration due to the patient remaining symptomatic on maximum tolerated acetazolamide. Intraocular pressure stabilized into target range and the optic nerve edema resolved. CONCLUSIONS Rarely, intraocular pressure reduction can unmask elevated intracranial pressure, leading to optic nerve edema. Optic nerve sheath fenestration is a practical therapeutic modality to consider when treating this occurrence.
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30
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Fleischman D, Kaskar O, Shams R, Zhang X, Olson D, Zdanski C, Thorp BD, Kuznetsov AV, Grace L, Lee YZ. A Novel Porcine Model for the Study of Cerebrospinal Fluid Dynamics: Development and Preliminary Results. Front Neurol 2019; 10:1137. [PMID: 31708863 PMCID: PMC6819502 DOI: 10.3389/fneur.2019.01137] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 10/10/2019] [Indexed: 12/02/2022] Open
Abstract
Idiopathic intracranial hypertension, space-flight associated neuro-ocular syndrome (SANS), and glaucoma are conditions that are among a spectrum of cerebrospinal fluid (CSF)-related ophthalmologic disease. This implies that local CSF pressures at the level of the optic nerve are involved to variable extent in these disease processes. However, CSF pressure measurements are problematic due to invasiveness and interpretation. The pressure measured by a lumbar puncture is likely not the same as the orbital CSF pressure. It is believed this is at least in part due to the flow restrictive properties of the optic canal. To investigate CSF flow within the orbit, a model for CSF dynamics was created using three medium-sized pigs. Contrast was administered through a lumbar subarachnoid space access. The contrast front was imaged with repeated computed tomographic (CT) imaging. Once contrast entered the orbit, rapid, sequential CT imaging was performed until the contrast reached the posterior globe. Head tilting was performed to highlight the role of gravitational dependence within the subarachnoid space.
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Affiliation(s)
- David Fleischman
- Department of Ophthalmology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Omkar Kaskar
- Department of Mechanical and Aerospace Engineering, NC State University, Raleigh, NC, United States
| | - Rayad Shams
- Department of Radiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Xinxin Zhang
- Department of Ophthalmology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Daniel Olson
- Department of Ophthalmology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Carlton Zdanski
- Department of Otolaryngology, Head & Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Brian D Thorp
- Department of Otolaryngology, Head & Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Andrey V Kuznetsov
- Department of Mechanical and Aerospace Engineering, NC State University, Raleigh, NC, United States
| | - Landon Grace
- Department of Mechanical and Aerospace Engineering, NC State University, Raleigh, NC, United States
| | - Yueh Z Lee
- Department of Radiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
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Ma Y, Pavlatos E, Clayson K, Pan X, Kwok S, Sandwisch T, Liu J. Mechanical Deformation of Human Optic Nerve Head and Peripapillary Tissue in Response to Acute IOP Elevation. Invest Ophthalmol Vis Sci 2019; 60:913-920. [PMID: 30835783 PMCID: PMC6402264 DOI: 10.1167/iovs.18-26071] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Purpose To measure the deformation of the human optic nerve head (ONH) and peripapillary tissue (PPT) in response to acute intraocular pressure (IOP) elevation. Methods The ONH and PPT of 14 human donor globes were imaged with high-frequency ultrasonography during inflation testing from 5 to 30 mm Hg. A correlation-based speckle tracking algorithm was used to compute tissue displacements, and the through-thickness, in-plane, and shear strains were calculated by using least-squares strain estimation methods. The ONH and PPT were segmented along the anterior-posterior direction and the nasal-temporal direction. Regional displacements and strains were analyzed and compared. Results The ONH displaced more posteriorly than the PPT in response to an acute IOP increase. Scleral canal expansion was minimal but correlated with ONH posterior displacement at all IOP levels. Through-thickness compression was concentrated in the anterior of both the ONH and the PPT. Shear was concentrated in the vicinity of the canal with higher shear in the peripheral ONH than the central ONH and higher shear in the PPT near the scleral canal than that further away from the canal. Conclusions High-resolution ultrasound speckle tracking showed a displacement mismatch between the ONH and the PPT, larger compressive strains in the direction of IOP loading in the anterior ONH and PPT, and higher shear strains in the periphery of ONH in response to acute IOP elevation in the human eye. These findings delineate the deformation patterns within and around the ONH and may help understand IOP-associated optic nerve damage.
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Affiliation(s)
- Yanhui Ma
- Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, United States
| | - Elias Pavlatos
- Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, United States
| | - Keyton Clayson
- Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, United States.,Biophysics Interdisciplinary Group, Ohio State University, Columbus, Ohio, United States
| | - Xueliang Pan
- Department of Biomedical Informatics, Ohio State University, Columbus, Ohio, United States
| | - Sunny Kwok
- Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, United States
| | - Thomas Sandwisch
- Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, United States
| | - Jun Liu
- Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, United States.,Biophysics Interdisciplinary Group, Ohio State University, Columbus, Ohio, United States.,Department of Ophthalmology and Visual Science, Ohio State University, Columbus, Ohio, United States
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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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Tun TA, Wang X, Baskaran M, Nongpiur ME, Tham YC, Perera SA, Strouthidis NG, Aung T, Cheng CY, Girard MJA. Variation of Peripapillary Scleral Shape With Age. Invest Ophthalmol Vis Sci 2019; 60:3275-3282. [PMID: 31369672 PMCID: PMC6675518 DOI: 10.1167/iovs.19-26777] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2019] [Accepted: 06/18/2019] [Indexed: 11/24/2022] Open
Abstract
Purpose To define the shape of the anterior surface of the peripapillary sclera (PPS) and evaluate its relationship with age and ocular determinants in a population-based Chinese cohort. Methods The optic nerve heads of 619 healthy Chinese subjects were imaged with spectral-domain optical coherence tomography. To assess the shape of the PPS/Bruch's membrane (BM), we measured the angle between a line parallel to the nasal anterior PPS/BM boundary and one parallel to the temporal side. A negative value indicated that the PPS/BM followed an inverted v-shaped configuration (peak pointing toward the vitreous), whereas a positive value indicated that it followed a v-shaped configuration (peak pointing toward the orbital tissues). A linear regression model was used to evaluate the relationship between the PPS angle and other ocular parameters. Results The mean PPS angle was 3.68° ± 6.73° and the BM angle was 9.69° ± 5.05°. The PPS angle increased on average by 0.233 deg/y. A v-shaped PPS was significantly associated with age (β = 0.087, P = 0.004), peripapillary choroidal thickness (β = -0.479, P < 0.001), lamina cribrosa depth (β = 0.307, P < 0.001), and BM angle (β = 0.487, P < 0.001) after adjusting for best corrected visual acuity, central corneal thickness, and axial length. Conclusions The anterior surface of PPS of an elderly adult population had a v-shaped configuration and was more pronounced with increasing age, thin peripapillary choroid, and a deep cup. Such a change in shape with age could have an impact on the biomechanical environment of the optic nerve head.
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Affiliation(s)
- Tin A. Tun
- Singapore Eye Research Institute and Singapore National Eye Centre, Singapore
- Ophthalmic Engineering & Innovation Laboratory, Department of Biomedical Engineering, National University of Singapore, Singapore
| | - Xiaofei Wang
- Ophthalmic Engineering & Innovation Laboratory, Department of Biomedical Engineering, National University of Singapore, Singapore
- Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Mani Baskaran
- Singapore Eye Research Institute and Singapore National Eye Centre, Singapore
- Duke-NUS Medical School, Singapore
| | - Monisha E. Nongpiur
- Singapore Eye Research Institute and Singapore National Eye Centre, Singapore
- Duke-NUS Medical School, Singapore
| | - Yih-Chung Tham
- Singapore Eye Research Institute and Singapore National Eye Centre, Singapore
| | - Shamira A. Perera
- Singapore Eye Research Institute and Singapore National Eye Centre, Singapore
- Duke-NUS Medical School, Singapore
| | - Nicholas G. Strouthidis
- Singapore Eye Research Institute and Singapore National Eye Centre, Singapore
- NIHR Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom
- Discipline of Clinical Ophthalmology and Eye Health, University of Sydney, Sydney, New South Wales, Australia
| | - Tin Aung
- Singapore Eye Research Institute and Singapore National Eye Centre, Singapore
- Duke-NUS Medical School, Singapore
- Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Ching-Yu Cheng
- Singapore Eye Research Institute and Singapore National Eye Centre, Singapore
- Duke-NUS Medical School, Singapore
- Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Michaël J. A. Girard
- Singapore Eye Research Institute and Singapore National Eye Centre, Singapore
- Ophthalmic Engineering & Innovation Laboratory, Department of Biomedical Engineering, National University of Singapore, Singapore
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Kim YW, Park KH. Exogenous influences on intraocular pressure. Br J Ophthalmol 2019; 103:1209-1216. [PMID: 30910873 DOI: 10.1136/bjophthalmol-2018-313381] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2018] [Revised: 02/08/2019] [Accepted: 03/02/2019] [Indexed: 02/05/2023]
Abstract
Intraocular pressure (IOP), the pressure within the eyeball, is a function mainly of the production and elimination of aqueous humour. Balanced IOP helps to maintain the eyeball contour, allowing proper refraction of light in the anterior segment of the eye. Increases in IOP can cause injury to the ocular structure, typically the optic nerve head and retinal ganglion cells. IOP increase, additionally, is a risk factor for glaucoma progression. However, it is not unusual that glaucoma worsens despite well-managed IOP; indeed, glaucoma can develop and progress even within the normal IOP range. IOP measured once during daytime office hours might not provide sufficient information for effective glaucoma management. In fact, IOP is not a fixed value but rather changes over time: it fluctuates with the intrinsic circadian rhythm and can also change in various lifestyle-related situations (eg, with body posture, during exercise, while holding breath and according to dietary habits). It is therefore worth exploring the various factors that can affect IOP and glaucoma risk. In this review, the various exogenous influences on IOP in the literature are investigated.
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Affiliation(s)
- Yong Woo Kim
- Ophthalmology, Seoul National University Hospital, Seoul, Republic of Korea
| | - Ki Ho Park
- Ophthalmology, Seoul National University College of Medicine, Seoul, Republic of Korea
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Pavlatos E, Ma Y, Clayson K, Pan X, Liu J. Regional Deformation of the Optic Nerve Head and Peripapillary Sclera During IOP Elevation. Invest Ophthalmol Vis Sci 2019; 59:3779-3788. [PMID: 30046819 PMCID: PMC6059763 DOI: 10.1167/iovs.18-24462] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Purpose To measure the deformation of the porcine optic nerve head (ONH) and peripapillary sclera (PPS) in response to intraocular pressure (IOP) elevation. Methods High-frequency ultrasound was used to image the ONH and PPS of 12 porcine eyes during ex vivo inflation testing from 5 to 30 mm Hg. A speckle tracking algorithm was used to compute tissue displacements in the anterior-posterior direction and expansion of the scleral canal. Through-thickness, in-plane, and shear strains were calculated within the ONH. Regional displacements and strains were analyzed and compared. Results The ONH and PPS showed overall posterior displacement in response to IOP elevation. Posterior displacement of the ONH was larger than and strongly correlated with the posterior displacement of the PPS throughout inflation testing. Scleral canal expansion was much smaller and leveled off quicker than ONH posterior displacement as IOP increased. Through-thickness compression was concentrated in the anterior ONH, which also experienced larger in-plane and shear strains than the posterior ONH. Within the anterior ONH, all three strains were significantly higher in the periphery compared with the center, with the shear strain exhibiting the greatest difference between the two regions. Conclusions High-resolution ultrasound speckle tracking revealed the full-thickness mechanical response of the posterior eye to IOP elevation. A mismatch in posterior displacement was found between the ONH and PPS, and regional analyses showed a concentration of strains within the periphery of the anterior porcine ONH. These deformation patterns may help in understanding IOP-associated optic nerve damage and glaucoma susceptibility.
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Affiliation(s)
- Elias Pavlatos
- Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, United States
| | - Yanhui Ma
- Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, United States
| | - Keyton Clayson
- Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, United States.,Biophysics Interdisciplinary Group, Ohio State University, Columbus, Ohio, United States
| | - Xueliang Pan
- Department of Biomedical Informatics, Ohio State University, Columbus, Ohio, United States
| | - Jun Liu
- Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, United States.,Biophysics Interdisciplinary Group, Ohio State University, Columbus, Ohio, United States.,Department of Ophthalmology and Visual Science, Ohio State University, Columbus, Ohio, United States
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36
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Huang L, Korhonen RK, Turunen MJ, Finnilä MAJ. Experimental mechanical strain measurement of tissues. PeerJ 2019; 7:e6545. [PMID: 30867989 PMCID: PMC6409087 DOI: 10.7717/peerj.6545] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 01/31/2019] [Indexed: 12/22/2022] Open
Abstract
Strain, an important biomechanical factor, occurs at different scales from molecules and cells to tissues and organs in physiological conditions. Under mechanical strain, the strength of tissues and their micro- and nanocomponents, the structure, proliferation, differentiation and apoptosis of cells and even the cytokines expressed by cells probably shift. Thus, the measurement of mechanical strain (i.e., relative displacement or deformation) is critical to understand functional changes in tissues, and to elucidate basic relationships between mechanical loading and tissue response. In the last decades, a great number of methods have been developed and applied to measure the deformations and mechanical strains in tissues comprising bone, tendon, ligament, muscle and brain as well as blood vessels. In this article, we have reviewed the mechanical strain measurement from six aspects: electro-based, light-based, ultrasound-based, magnetic resonance-based and computed tomography-based techniques, and the texture correlation-based image processing method. The review may help solving the problems of experimental and mechanical strain measurement of tissues under different measurement environments.
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Affiliation(s)
- Lingwei Huang
- Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
| | - Rami K Korhonen
- Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
| | - Mikael J Turunen
- Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
| | - Mikko A J Finnilä
- Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.,Research Unit of Medical Imaging, Physics and Technology, University of Oulu, Oulu, Finland.,Medical Research Center Oulu, Oulu University Hospital, Oulu, Finland
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37
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Qiu C, Chen M, Yao J, Sun X, Xu J, Zhang R, Wang X, Li G, Qian S. Mechanical Strain Induces Distinct Human Scleral Fibroblast Lineages: Differential Roles in Cell Proliferation, Apoptosis, Migration, and Differentiation. Invest Ophthalmol Vis Sci 2019; 59:2401-2410. [PMID: 29847646 DOI: 10.1167/iovs.18-23855] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose The purpose of this study was to explore the effect of mechanical strain on human scleral fibroblasts (HSFs) and compare cell behaviors of HSFs from distinct regions. Methods Primary HSFs were cultivated using a digestive protocol. Cells were seeded on collagen I-coated Bioflex plates, and a FX-5000 tension system was used to perform biaxial mechanical strain in vitro. We applied 10%, 0.5-Hz mechanical strain. Cell behaviors of peripapillary and periphery HSFs were compared after the strain. Edu imaging, Cell Counting Kit-8 assay, and cell cycle flow cytometry were conducted to analyze cell proliferation ability. For cell apoptosis, flow cytometry of Annexin V/propidium iodide, caspase 3 activity, and Western blot were performed. Immunofluorescence, real-time PCR, and Western blot were used to investigate cell differentiation. A migration assay was also performed. Results Under the mechanical strain of 10%, 0.5 Hz for 24 hours, the proliferation ability and cell apoptosis of peripapillary HSFs did not have a significant change. The expression of alpha-smooth muscle actin (α-SMA) slightly decreased. However, increased cell proliferation, attenuated cell apoptosis and more expression of α-SMA were shown in the periphery HSFs under the same condition. The migration rate was also increased for periphery HSFs, whereas it kept almost the same for peripapillary HSFs under 10%, 0.5-Hz strain for 8 hours. Conclusions Mechanical strain affected the cell behaviors of HSFs. The different performance of cells from distinct regions may suggest familial linages of HSFs, probably induced by mechanical strain.
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Affiliation(s)
- Chen Qiu
- Department of Ophthalmology, Eye and Ear, Nose, Throat Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,Key Laboratory of Myopia, Ministry of Health, Fudan University, Shanghai, China
| | - Minjie Chen
- Department of Ophthalmology, Eye and Ear, Nose, Throat Hospital, Shanghai Medical College, Fudan University, Shanghai, China
| | - Jing Yao
- Department of Ophthalmology, Eye and Ear, Nose, Throat Hospital, Shanghai Medical College, Fudan University, Shanghai, China
| | - Xinghuai Sun
- Department of Ophthalmology, Eye and Ear, Nose, Throat Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,Key Laboratory of Myopia, Ministry of Health, Fudan University, 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
| | - Jianjiang Xu
- Department of Ophthalmology, Eye and Ear, Nose, Throat Hospital, Shanghai Medical College, Fudan University, Shanghai, China
| | - Rong Zhang
- Department of Ophthalmology, Eye and Ear, Nose, Throat Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,Key Laboratory of Myopia, Ministry of Health, Fudan University, Shanghai, China
| | - Xin Wang
- Department of Ophthalmology, Eye and Ear, Nose, Throat Hospital, Shanghai Medical College, Fudan University, Shanghai, China
| | - Gang Li
- Department of Ophthalmology, Eye and Ear, Nose, Throat Hospital, Shanghai Medical College, Fudan University, Shanghai, China
| | - Shaohong Qian
- Department of Ophthalmology, Eye and Ear, Nose, Throat Hospital, Shanghai Medical College, Fudan University, Shanghai, China
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A finite element study of posterior eye biomechanics: The influence of intraocular and cerebrospinal pressure on the optic nerve head, peripapillary region, subarachnoid space and meninges. INFORMATICS IN MEDICINE UNLOCKED 2019. [DOI: 10.1016/j.imu.2019.100185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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39
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Umfress AC, Mawn LA, Joos KM. Short-term Optic Disc Cupping Reversal in a Patient With Mild Juvenile Open-angle Glaucoma Due to Early Idiopathic Intracranial Hypertension. J Glaucoma 2018; 28:e53-e57. [PMID: 30531192 DOI: 10.1097/ijg.0000000000001151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE The purpose of this study was to report a case of optic disc cupping reversal in an adult without significant intraocular pressure-lowering treatment. PATIENT A 20-year-old female with a history of mild juvenile open-angle glaucoma who developed subjective blurred vision and a decrease in cupping of her optic discs. RESULTS Dilated examination demonstrated decreased cup-to-disc ratios in both eyes with a slight blurring of the disc margin in the right eye. The appearance of both optic discs returned to baseline after weight loss therapy. CONCLUSIONS An unexplained reduction of optic nerve cup-to-disc ratio should prompt a workup for other etiologies, such as increased intracranial pressure. Baseline photographs not subjected to computerized scan obsolescence are extremely useful in monitoring the long-term appearance of asymmetric optic discs as an adjunct to the clinical examination.
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Affiliation(s)
- Allison C Umfress
- Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, TN
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40
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Enlarged Optic Nerve Axons and Reduced Visual Function in Mice with Defective Microfibrils. eNeuro 2018; 5:eN-NWR-0260-18. [PMID: 30406200 PMCID: PMC6220594 DOI: 10.1523/eneuro.0260-18.2018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Accepted: 10/13/2018] [Indexed: 01/13/2023] Open
Abstract
Glaucoma is a leading cause of irreversible vision loss due to retinal ganglion cell (RGC) degeneration that develops slowly with age. Elevated intraocular pressure (IOP) is a significant risk factor, although many patients develop glaucoma with IOP in the normal range. Mutations in microfibril-associated genes cause glaucoma in animal models, suggesting the hypothesis that microfibril defects contribute to glaucoma. To test this hypothesis, we investigated IOP and functional/structural correlates of RGC degeneration in mice of either sex with abnormal microfibrils due to heterozygous Tsk mutation of the fibrilin-1 gene (Fbn1Tsk/+). Although IOP was not affected, Fbn1Tsk/+ mice developed functional deficits at advanced age consistent with glaucoma, including reduced RGC responses in electroretinogram (ERG) experiments. While RGC density in the retina was not affected, the density of RGC axons in the optic nerve was significantly reduced in Fbn1Tsk/+ mice. However, reduced axon density correlated with expanded optic nerves, resulting in similar numbers of axons in Fbn1Tsk/+ and control nerves. Axons in the optic nerves of Fbn1Tsk/+ mice were significantly enlarged and axon diameter was strongly correlated with optic nerve area, as has been reported in early pathogenesis of the DBA/2J mouse model of glaucoma. Our results suggest that microfibril abnormalities can lead to phenotypes found in early-stage glaucomatous neurodegeneration. Thinning of the elastic fiber-rich pia mater was found in Fbn1Tsk/+ mice, suggesting mechanisms allowing for optic nerve expansion and a possible biomechanical contribution to determination of axon caliber.
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In vivo optic nerve head mechanical response to intraocular and cerebrospinal fluid pressure: imaging protocol and quantification method. Sci Rep 2018; 8:12639. [PMID: 30140057 PMCID: PMC6107503 DOI: 10.1038/s41598-018-31052-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 08/09/2018] [Indexed: 01/22/2023] Open
Abstract
This study presents a quantification method for the assessment of the optic nerve head (ONH) deformations of the living human eye under acute intraocular pressure (IOP) elevation and change of cerebrospinal fluid pressure (CSFP) with body position. One eye from a brain-dead organ donor with open-angle glaucoma was imaged by optical coherence tomography angiography during an acute IOP and CSFP elevation test. Volumetric 3D strain was computed by digital volume correlation. With increase in IOP the shear strain consistently increased in both sitting and supine position (p < 0.001). When CSFP was increased at constant IOP by changing body position, a global reduction in the ONH strain was observed (−0.14% p = 0.0264). Strain in the vasculature was significantly higher than in the structural tissue (+0.90%, p = 0.0002). Retinal nerve fiber layer (RNFL) thickness strongly associated (ρ = −0.847, p = 0.008) with strain in the peripapillary sclera (ppScl) but not in the retina (p = 0.433) and lamina (p = 0.611). These initial results show that: CSFP independently to IOP modulates strain in the human ONH; ppScl strains are greater than strains in lamina and retina; strain in the retinal vasculature was higher than in the structural tissue; In this glaucoma eye, higher ppScl strain associated with lower RNFL thickness.
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42
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Chuangsuwanich T, Moothanchery M, Tsz Chung Yan A, Schmetterer L, Girard MJA, Pramanik M. Photoacoustic imaging of lamina cribrosa microcapillaries in porcine eyes. APPLIED OPTICS 2018; 57:4865-4871. [PMID: 30118104 DOI: 10.1364/ao.57.004865] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Accepted: 05/17/2018] [Indexed: 05/18/2023]
Abstract
Due to the embedded nature of the lamina cribrosa (LC) microcapillary network, conventional imaging techniques have failed to obtain the high-resolution images needed to assess the perfusion state of the LC. In this study, both optical resolution (OR) and acoustic resolution (AR) photoacoustic microscopy (PAM) techniques were used to obtain static and dynamic information about LC perfusion in ex vivo porcine eyes. The OR-PAM system could resolve a perfused LC microcapillary network with a lateral resolution of 4.2 μm and also provided good depth information (33 μm axial resolution) to visualize through-thickness vascular variations. The AR-PAM system was capable of detecting time-dependent perfusion variations. This study represents the first step towards using an emerging imaging modality (PAM) to study the LC's perfusion, which could be a basis for further investigation of the hemodynamic aspects of glaucomatous optic neuropathy.
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Jóhannesson G, Eklund A, Lindén C. Intracranial and Intraocular Pressure at the Lamina Cribrosa: Gradient Effects. Curr Neurol Neurosci Rep 2018; 18:25. [PMID: 29651628 PMCID: PMC5897485 DOI: 10.1007/s11910-018-0831-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
PURPOSE OF REVIEW A pressure difference between the intraocular and intracranial compartments at the site of the lamina cribrosa has been hypothesized to have a pathophysiological role in several optic nerve head diseases. This paper reviews the current literature on the translamina cribrosa pressure difference (TLCPD), the associated pressure gradient, and its potential pathophysiological role, as well as the methodology to assess TLCPD. RECENT FINDINGS For normal-tension glaucoma (NTG), initial studies indicated low intracranial pressure (ICP) while recent findings indicate that a reduced ICP is not mandatory. Data from studies on the elevated TLCPD as a pathophysiological factor of NTG are equivocal. From the identification of potential postural effects on the cerebrospinal fluid (CSF) communication between the intracranial and retrolaminar space, we hypothesize that the missing link could be a dysfunction of an occlusion mechanism of the optic nerve sheath around the optic nerve. In upright posture, this could cause an elevated TLCPD even with normal ICP and we suggest that this should be investigated as a pathophysiological component in NTG patients.
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Affiliation(s)
- Gauti Jóhannesson
- Department of Clinical Sciences, Ophthalmology, Umeå University, Umeå, Sweden. .,Wallenberg Centre for Molecular Medicine, Umeå University, Umeå, Sweden.
| | - Anders Eklund
- Department of Radiation Sciences, Biomedical Engineering, Umeå University, Umeå, Sweden
| | - Christina Lindén
- Department of Clinical Sciences, Ophthalmology, Umeå University, Umeå, Sweden
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Zhao D, Nguyen CTO, He Z, Wong VHY, van Koeverden AK, Vingrys AJ, Bui BV. Age-related changes in the response of retinal structure, function and blood flow to pressure modification in rats. Sci Rep 2018; 8:2947. [PMID: 29440700 PMCID: PMC5811482 DOI: 10.1038/s41598-018-21203-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 01/29/2018] [Indexed: 12/11/2022] Open
Abstract
Age-related changes to the balance between the pressure inside the eye (intraocular pressure, IOP) and the pressure inside the brain (intracranial pressure, ICP) can modify the risk of glaucoma. In this study, we consider whether the optic nerve in older rat eyes is more susceptible to acute IOP and ICP modification. We systematically manipulate both ICP and IOP and quantify their effects on ganglion cell function (electroretinography, ERG), optic nerve structure (optical coherence tomography, OCT) and retinal blood flow (Doppler OCT). We show that ganglion cell function in older eyes was more susceptible to a higher optic nerve pressure difference (ONPD = IOP - ICP). This age-related susceptibility could not be explained by poorer blood flow with elevated ONPD. Rather, as ONPD increased the retinal nerve fibre layer showed greater compression, and the retinal surface showed less deformation in older eyes. Our data suggest that age-related changes to connective tissues in and around the rat optic nerve make it less flexible, which may result in greater strain on ganglion cell axons. This may account for greater functional susceptibility to higher optic nerve pressure differences in older rat eyes. Further studies in a species with a well-developed lamina cribrosa are needed to determine the clinical importance of these observations.
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Affiliation(s)
- Da Zhao
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Christine T O Nguyen
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Zheng He
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Vickie H Y Wong
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Anna K van Koeverden
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Algis J Vingrys
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Bang V Bui
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, 3010, Victoria, Australia.
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Lindén C, Qvarlander S, Jóhannesson G, Johansson E, Östlund F, Malm J, Eklund A. Normal-Tension Glaucoma Has Normal Intracranial Pressure: A Prospective Study of Intracranial Pressure and Intraocular Pressure in Different Body Positions. Ophthalmology 2017; 125:361-368. [PMID: 29096996 DOI: 10.1016/j.ophtha.2017.09.022] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Revised: 09/14/2017] [Accepted: 09/19/2017] [Indexed: 11/18/2022] Open
Abstract
PURPOSE To test the hypothesis that normal-tension glaucoma (NTG) is caused by an increased pressure difference across the lamina cribrosa (LC) related to a low intracranial pressure (ICP). DESIGN Prospective case-control study. PARTICIPANTS Thirteen NTG patients (9 women; median 71 [range: 56-83] years) were recruited for investigation with the same protocol as 11 healthy volunteers (8 women; 47 [30-59] years). A larger control group (n = 51; 30 women; 68 [30-81] years) was used only for ICP comparison in supine position. METHODS ICP and intraocular pressure (IOP) were simultaneously measured in supine, sitting, and 9° head-down tilt (HDT) positions. Trans-lamina cribrosa pressure difference (TLCPD) was calculated using ICP and IOP together with geometric distances estimated from magnetic resonance imaging to adjust for hydrostatic effects. MAIN OUTCOME MEASURES ICP, IOP, and TLCPD in different body positions. RESULTS Between NTG patients and healthy volunteers, there were no differences in ICP, IOP, or TLCPD in supine, sitting, or HDT (P ≥ 0.11), except for IOP in HDT (P = 0.04). There was no correlation between visual field defect and TLCPD, IOP, or ICP and in any body position (P ≥ 0.39). Mean ICP in supine was 10.3 mmHg (SD = 2.7) in the NTG group (n = 13) and 11.3 (2.2) mmHg in the larger control group (n = 51) (P = 0.24). CONCLUSIONS There was no evidence of reduced ICP in NTG patients as compared with healthy controls, either in supine or in upright position. Consequently, the hypothesis that NTG is caused by an elevated TLCPD from low ICP was not supported.
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Affiliation(s)
- Christina Lindén
- Department of Clinical Sciences, Ophthalmology, Umeå University, Umeå, Sweden.
| | - Sara Qvarlander
- Department of Radiation Sciences, Biomedical Engineering, Umeå University, Umeå, Sweden
| | - Gauti Jóhannesson
- Department of Clinical Sciences, Ophthalmology, Umeå University, Umeå, Sweden
| | - Elias Johansson
- Department of Pharmacology and Clinical Neuroscience, Neurology, Umeå University, Umeå, Sweden
| | - Fanny Östlund
- Department of Clinical Sciences, Ophthalmology, Umeå University, Umeå, Sweden
| | - Jan Malm
- Department of Pharmacology and Clinical Neuroscience, Neurology, Umeå University, Umeå, Sweden
| | - Anders Eklund
- Department of Radiation Sciences, Biomedical Engineering, Umeå University, Umeå, Sweden; Umeå Center for Functional Brain Imaging, Umeå University, Umeå, Sweden
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Marshall-Goebel K, Terlević R, Gerlach DA, Kuehn S, Mulder E, Rittweger J. Lower body negative pressure reduces optic nerve sheath diameter during head-down tilt. J Appl Physiol (1985) 2017; 123:1139-1144. [PMID: 28818998 DOI: 10.1152/japplphysiol.00256.2017] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 08/14/2017] [Accepted: 08/14/2017] [Indexed: 01/06/2023] Open
Abstract
The microgravity ocular syndrome (MOS) results in significant structural and functional ophthalmic changes during 6-mo spaceflight missions consistent with an increase in cerebrospinal fluid (CSF) pressure compared with the preflight upright position. A ground-based study was performed to assess two of the major hypothesized contributors to MOS, headward fluid shifting and increased ambient CO2, on intracranial and periorbital CSF. In addition, lower body negative pressure (LBNP) was assessed as a countermeasure to headward fluid shifting. Nine healthy male subjects participated in a crossover design study with five head-down tilt (HDT) conditions: -6, -12, and -18° HDT, -12° HDT with -20 mmHg LBNP, and -12° HDT with a 1% CO2 environment, each for 5 h total. A three-dimensional volumetric scan of the cranium and transverse slices of the orbita were collected with MRI, and intracranial CSF volume and optic nerve sheath diameter (ONSD) were measured after 4.5 h HDT. ONSD increased during -6° (P < 0.001), -12° (P < 0.001), and -18° HDT (P < 0.001) and intracranial CSF increased during -12° HDT (P = 0.01) compared with supine baseline. Notably, LBNP was able to reduce the increases in ONSD and intracranial CSF during HDT. The addition of 1% CO2 during HDT, however, had no further effect on ONSD, but rather ONSD increased from baseline in a similar magnitude to -12° HDT with ambient air (P = 0.001). These findings demonstrate the ability of LBNP, a technique that targets fluid distribution in the lower limbs, to directly influence CSF and may be a promising countermeasure to help reduce increases in CSF.NEW & NOTEWORTHY This is the first study to demonstrate the ability of lower body negative pressure to directly influence cerebrospinal fluid surrounding the optic nerve, indicating potential use as a countermeasure for increased cerebrospinal fluid on Earth or in space.
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Affiliation(s)
- Karina Marshall-Goebel
- Neural Systems Group, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts; .,Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
| | - Robert Terlević
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany.,International Space University, Illkirch-Graffenstaden, France; and
| | - Darius A Gerlach
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
| | - Simone Kuehn
- University Clinic Hamburg-Eppendorf, Clinic for Psychiatry and Psychotherapy, Hamburg, Germany
| | - Edwin Mulder
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
| | - Jörn Rittweger
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
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