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Lu Y, Hua Y, Wang B, Zhong F, Theophanous A, Tahir S, Lee PY, Sigal IA. The Robust Lamina Cribrosa Vasculature: Perfusion and Oxygenation Under Elevated Intraocular Pressure. Invest Ophthalmol Vis Sci 2024; 65:1. [PMID: 38691092 PMCID: PMC11077910 DOI: 10.1167/iovs.65.5.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Accepted: 03/21/2024] [Indexed: 05/03/2024] Open
Abstract
Purpose Elevated intraocular pressure (IOP) is thought to cause lamina cribrosa (LC) blood vessel distortions and potentially collapse, adversely affecting LC hemodynamics, reducing oxygenation, and triggering, or contributing to, glaucomatous neuropathy. We assessed the robustness of LC perfusion and oxygenation to vessel collapses. Methods From histology, we reconstructed three-dimensional eye-specific LC vessel networks of two healthy monkey eyes. We used numerical simulations to estimate LC perfusion and from this the oxygenation. We then evaluated the effects of collapsing a fraction of LC vessels (0%-36%). The collapsed vessels were selected through three scenarios: stochastic (collapse randomly), systematic (collapse strictly by the magnitude of local experimentally determined IOP-induced compression), and mixed (a combination of stochastic and systematic). Results LC blood flow decreased linearly as vessels collapsed-faster for stochastic and mixed scenarios and slower for the systematic one. LC regions suffering severe hypoxia (oxygen <8 mm Hg) increased proportionally to the collapsed vessels in the systematic scenario. For the stochastic and mixed scenarios, severe hypoxia did not occur until 15% of vessels collapsed. Some LC regions had higher perfusion and oxygenation as vessels collapsed elsewhere. Some severely hypoxic regions maintained normal blood flow. Results were equivalent for both networks and patterns of experimental IOP-induced compression. Conclusions LC blood flow was sensitive to distributed vessel collapses (stochastic and mixed) and moderately vulnerable to clustered collapses (systematic). Conversely, LC oxygenation was robust to distributed vessel collapses and sensitive to clustered collapses. Locally normal flow does not imply adequate oxygenation. The actual nature of IOP-induced vessel collapse remains unknown.
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Affiliation(s)
- Yuankai Lu
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Yi Hua
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Department of Biomedical Engineering, University of Mississippi, Mississippi, United States
- Department of Mechanical Engineering, University of Mississippi, Mississippi, United States
| | - Bingrui Wang
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Fuqiang Zhong
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Andrew Theophanous
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Shaharoz Tahir
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Po-Yi Lee
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Ian A. Sigal
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
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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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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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Voorhees AP, Hua Y, Brazile BL, Wang B, Waxman S, Schuman JS, Sigal IA. So-Called Lamina Cribrosa Defects May Mitigate IOP-Induced Neural Tissue Insult. Invest Ophthalmol Vis Sci 2021; 61:15. [PMID: 33165501 PMCID: PMC7671862 DOI: 10.1167/iovs.61.13.15] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Purpose The prevailing theory about the function of lamina cribrosa (LC) connective tissues is that they provide structural support to adjacent neural tissues. Missing connective tissues would compromise this support and therefore are regarded as “LC defects”, despite scarce actual evidence of their role. We examined how so-called LC defects alter IOP-related mechanical insult to the LC neural tissues. Methods We built numerical models incorporating LC microstructure from polarized light microscopy images. To simulate LC defects of varying sizes, individual beams were progressively removed. We then compared intraocular pressure (IOP)-induced neural tissue deformations between models with and without defects. To better understand the consequences of defect development, we also compared neural tissue deformations between models with partial and complete loss of a beam. Results The maximum stretch of neural tissues decreased non-monotonically with defect size. Maximum stretch in the model with the largest defect decreased by 40% in comparison to the model with no defects. Partial loss of a beam increased the maximum stretch of neural tissues in its adjacent pores by 162%, compared with 63% in the model with complete loss of a beam. Conclusions Missing LC connective tissues can mitigate IOP-induced neural tissue insult, suggesting that the role of the LC connective tissues is more complex than simply fortifying against IOP. The numerical models further predict that partial loss of a beam is biomechanically considerably worse than complete loss of a beam, perhaps explaining why defects have been reported clinically but partial beams have not.
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Affiliation(s)
- Andrew P Voorhees
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Yi Hua
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Bryn L Brazile
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Bingrui Wang
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States.,School of Mechanical Engineering, Southwest Jiaotong University, Chengdu, Sichuan, China
| | - Susannah Waxman
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Joel S Schuman
- Department of Ophthalmology, NYU Langone Health, New York University Grossman School of Medicine, New York, New York, United States.,Center for Neural Science, New York University, New York, New York, United States.,Department of Biomedical Engineering, New York University Tandon School of Engineering, Brooklyn, New York, United States.,Department of Physiology and Neuroscience, Neuroscience Institute, NYU Langone Health, New York University Grossman School of Medicine, New York, New York, United States
| | - Ian A Sigal
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States.,Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States.,McGowan Institute for Regenerative Medicine, University of Pittsburgh Medical Center and University of Pittsburgh, Pittsburgh, Pennsylvania, United States.,Louis J. Fox Center for Vision Restoration, University of Pittsburgh Medical Center and University of Pittsburgh, Pittsburgh, Pennsylvania, United States
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Fazio MA, Gardiner SK, Bruno L, Hubbard M, Bianco G, Karuppanan U, Kim J, El Hamdaoui M, Grytz R, Downs JC, Girkin CA. Histologic validation of optical coherence tomography-based three-dimensional morphometric measurements of the human optic nerve head: Methodology and preliminary results. Exp Eye Res 2021; 205:108475. [PMID: 33516762 PMCID: PMC8044038 DOI: 10.1016/j.exer.2021.108475] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 01/12/2021] [Accepted: 01/22/2021] [Indexed: 11/16/2022]
Abstract
PURPOSE To compare the three-dimensional (3D) morphology of the deep load-bearing structures of the human optic nerve head (ONH) as revealed in vivo by spectral domain optical coherence tomography (SDOCT) with ex vivo quantitative 3D histology. METHODS SDOCT imaging of the ONH was performed in six eyes from three brain-dead organ donors on life-support equipment awaiting organ procurement (in vivo conditions). Following organ procurement (ex vivo conditions), the eyes were enucleated and underwent a pars plana vitrectomy followed by pressurization to physiologic IOP and immersion fixation. Ex vivo ONH morphology was obtained from high-fidelity episcopic fluorescent 3D reconstruction. Morphologic parameters of the observed ONH canal geometry and peripapillary choroid, as well as the shape, visibility and depth of the lamina cribrosa were compared between ex vivo and in vivo measurements using custom software to align, scale, and manually delineate the different regions of the ONH. RESULTS There was significant correspondence between in vivo and ex vivo measurements of the depth and shape of the lamina cribrosa, along with the size and shape of Bruch's membrane opening (BMO) and anterior scleral canal opening (ASCO). Weaker correspondence was observed for choroidal thickness; as expected, a thinner choroid was seen ex vivo due to loss of blood volume upon enucleation (-79.9%, p < 0.001). In addition, the lamina was shallower (-32.3%, p = 0.0019) and BMO was smaller ex vivo (-3.38%, p = 0.026), suggesting post mortem shrinkage of the fixed tissue. On average, while highly variable, only 31% of the anterior laminar surface was visible in vivo with SDOCT (p < 0.001). CONCLUSIONS Morphologic parameters by SDOCT imaging of the deep ONH showed promising correspondence to histology metrics. Small but significant shrinkage artifact, along with large effects of exsanguination of the choroid, was seen in the ex vivo reconstructions of fixed tissues that may impact the quantification of ex vivo histoarchitecture, and this should be considered when developing models and biomarkers based on ex vivo imaging of fixed tissue. Lack of visibly of most of the lamina surface in SDOCT images is an important limitation to metrics and biomarkers based on in vivo images of the ONH deep tissues.
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Affiliation(s)
- Massimo A Fazio
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, United States; Department of Biomedical Engineering, The University of Alabama at Birmingham, Birmingham, AL, United States; The Viterbi Family Department of Ophthalmology, University of California, San Diego, San Diego, CA, United States.
| | - Stuart K Gardiner
- Devers Eye Institute, Discoveries in Sight, Legacy Health, Portland, OR, United States
| | - Luigi Bruno
- Department of Mechanical, Energy and Management Engineering, University of Calabria, Rende, CS, Italy
| | - Meredith Hubbard
- Department of Neurobiology, The University of Alabama at Birmingham, Birmingham, AL, United States
| | - Gianfranco Bianco
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Udayakumar Karuppanan
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Jihee Kim
- Department of Biomedical Engineering, The University of Alabama at Birmingham, Birmingham, AL, United States
| | - Mustapha El Hamdaoui
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Rafael Grytz
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, United States
| | - J Crawford Downs
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Christopher A Girkin
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, United States
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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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