1
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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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2
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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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3
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Machiele R, Frankfort BJ, Killer HE, Fleischman D. Problems in CSF and Ophthalmic Disease Research. FRONTIERS IN OPHTHALMOLOGY 2022; 2:896680. [PMID: 38983539 PMCID: PMC11182282 DOI: 10.3389/fopht.2022.896680] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Accepted: 05/30/2022] [Indexed: 07/11/2024]
Abstract
There has been significant interest and progress in the understanding of cerebrospinal fluid pressure and its relationship to glaucoma and other ophthalmic diseases. However, just as every physiologic fluid pressure fluctuates, cerebrospinal fluid pressure (CSFP) is similarly dynamic. Coupling this with the difficulty in measuring the pressure, there are many obstacles in furthering this field of study. This review highlights some of the difficulties in CSFP research, including fluid compartmentalization, estimation equations, and pressure fluctuation. Keeping these limitations in mind will hopefully improve the quality and context of this burgeoning field.
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Affiliation(s)
- Ryan Machiele
- Department of Ophthalmology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | | | - Hanspeter Esriel Killer
- Department of Ophthalmology, Kantonsspital Aarau, Aarau, Switzerland
- Center for Biomedicine University of Basel, Basel, Switzerland
| | - David Fleischman
- Department of Ophthalmology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
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4
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Hearon CM, Dias KA, Babu G, Marshall JET, Leidner J, Peters K, Silva E, MacNamara JP, Campain J, Levine BD. Effect of Nightly Lower Body Negative Pressure on Choroid Engorgement in a Model of Spaceflight-Associated Neuro-ocular Syndrome: A Randomized Crossover Trial. JAMA Ophthalmol 2021; 140:59-65. [PMID: 34882176 DOI: 10.1001/jamaophthalmol.2021.5200] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Importance Astronauts returning from long-duration spaceflight experience ocular remodeling related to cephalad fluid shifts induced by microgravity. It is hypothesized that the absence of diurnal reductions in intracranial pressure in microgravity creates a low but persistent pressure gradient at the posterior aspect of the eye, which results in ocular remodeling and space-associated neuro-ocular syndrome (SANS) over many months. Objective To determine whether partial reintroduction of footward fluid shifts during simulated microgravity via lower body negative pressure (LBNP) during sleep attenuates choroid engorgement, an early marker of ocular remodeling related to SANS. Design, Setting, and Participants Between May 2019 and February 2020, participants with no major cardiovascular, kidney, or ophthalmic disease completed 3 days of supine (0°) bed rest with and 3 days without 8 hours of nightly LBNP in a randomized, crossover design. This single-center investigation took place at the UT Southwestern Medical Center. All analyses were conducted blinded to condition and time point. Interventions Eight hours of nightly LBNP (-20 mm Hg) vs no LBNP. Main Outcomes and Measures The primary outcome was the change in choroid area and volume after 3 days of bed rest measured by optical coherence tomography. Results Of 10 participants, 5 were female, the mean (SD) age was 29 (9) years, and the age range was 18 to 55 years. Central venous pressure increased from the seated to supine position (mean [SD], seated: -2.3 [2.0] vs supine: 6.9 [2.0] mm Hg; P < .001), leading to choroid engorgement over 3 days of bed rest (Δ area: +0.09 mm2 [95% CI, 0.04-0.13]; P = .001; Δ volume: +0.37 mm3 [95% CI, 0.19-0.55]; P = .001). Nightly LBNP caused a sustained reduction in supine central venous pressure (mean [SD], 5.7 [2.2] mm Hg to 1.2 [1.4 mm Hg]; P < .001) and attenuated the increase in choroid area (74%) (Δ: 0.02 mm2 [95% -0.02 to 0.06]; P = .01) and volume (53%) (Δ: 0.17 mm3 [95% CI, 0.01-0.34]; P = .05) compared with control. Conclusions and Relevance Nightly LBNP reinstated a footward fluid shift and mitigated the increase in choroid area and volume. LBNP during sleep may be an effective countermeasure for ocular remodeling and SANS during long-duration space missions.
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Affiliation(s)
- Christopher M Hearon
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas.,University of Texas Southwestern Medical Center, Dallas
| | - Katrin A Dias
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas.,University of Texas Southwestern Medical Center, Dallas
| | - Gautam Babu
- University of Texas Southwestern Medical Center, Dallas
| | | | - James Leidner
- Internal Medicine, Texas Health Presbyterian Hospital Dallas, Dallas
| | - Kirsten Peters
- University Medical Center, Radboud University, Nijmegen, the Netherlands
| | - Erika Silva
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas
| | - James P MacNamara
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas.,University of Texas Southwestern Medical Center, Dallas
| | | | - Benjamin D Levine
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas.,University of Texas Southwestern Medical Center, Dallas
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5
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Li S, Wang C, Wu Z. Dietary L-arginine supplementation of tilapia (Oreochromis niloticus) alters the microbial population and activates intestinal fatty acid oxidation. Amino Acids 2021; 54:339-351. [PMID: 34212252 DOI: 10.1007/s00726-021-03018-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Accepted: 06/08/2021] [Indexed: 12/15/2022]
Abstract
Currently, little is known about the function of L-arginine in the homeostasis of intestinal lipid metabolism. This study was conducted to test the hypothesis that dietary L-arginine supplementation may alter intestinal microbiota and lipid metabolism in tilapia. Tilapia were fed a basal diet (containing 16.9 g L-arginine per kilogram diets) or the basal diet supplemented with 1% or 2% L-arginine for 8 wks. In the present study, we found that dietary supplementation with 1% or 2% L-arginine induced a shift in the community structure of gut microbiota, as showed by increased (p < 0.05) α-diversity, altered (p < 0.05) β-diversity and function profile. This finding coincided with decreased lipid accretion in the intestine of tilapia, which was associated with an enhancement in mRNA levels for peroxisome proliferator-activated receptor α (Pparα), acyl-coenzyme a oxidase 1 (Acox1), and peroxisome proliferator-activated receptor γ coactivator-1α (Pgc-1α). Using intestinal epithelial cell culture, we demonstrated that the lipid-lowering effect of L-arginine was mainly mediated by activating the AMP-activated protein kinase (AMPK) signaling pathway, carnitine palmitoyltransferase 1 (CPT1), and PPARα, as well as mRNA levels for Acox1 and Acox2. Collectively, our results suggest that dietary L-arginine supplementation of tilapia changed the intestinal microbiota and activated intestinal fatty acid oxidation. However, future studies are warranted to determine the relationship between microbiota and lipid metabolism in the intestine.
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Affiliation(s)
- Senlin Li
- State Key Laboratory of Animal Nutrition, Department of Animal Nutrition and Feed Science, China Agricultural University, Beijing, 100193, China
| | - Chao Wang
- College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Zhenlong Wu
- State Key Laboratory of Animal Nutrition, Department of Animal Nutrition and Feed Science, China Agricultural University, Beijing, 100193, China. .,Beijing Advanced Innovation Center for Food Nutrition and Human Health, China Agricultural University, Beijing, 100193, China.
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6
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Willey JS, Britten RA, Blaber E, Tahimic CG, Chancellor J, Mortreux M, Sanford LD, Kubik AJ, Delp MD, Mao XW. The individual and combined effects of spaceflight radiation and microgravity on biologic systems and functional outcomes. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART C, TOXICOLOGY AND CARCINOGENESIS 2021; 39:129-179. [PMID: 33902391 PMCID: PMC8274610 DOI: 10.1080/26896583.2021.1885283] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Both microgravity and radiation exposure in the spaceflight environment have been identified as hazards to astronaut health and performance. Substantial study has been focused on understanding the biology and risks associated with prolonged exposure to microgravity, and the hazards presented by radiation from galactic cosmic rays (GCR) and solar particle events (SPEs) outside of low earth orbit (LEO). To date, the majority of the ground-based analogues (e.g., rodent or cell culture studies) that investigate the biology of and risks associated with spaceflight hazards will focus on an individual hazard in isolation. However, astronauts will face these challenges simultaneously Combined hazard studies are necessary for understanding the risks astronauts face as they travel outside of LEO, and are also critical for countermeasure development. The focus of this review is to describe biologic and functional outcomes from ground-based analogue models for microgravity and radiation, specifically highlighting the combined effects of radiation and reduced weight-bearing from rodent ground-based tail suspension via hind limb unloading (HLU) and partial weight-bearing (PWB) models, although in vitro and spaceflight results are discussed as appropriate. The review focuses on the skeletal, ocular, central nervous system (CNS), cardiovascular, and stem cells responses.
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Affiliation(s)
| | | | - Elizabeth Blaber
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute
| | | | | | - Marie Mortreux
- Department of Neurology, Harvard Medical School, Beth Israel Deaconess Medical Center
| | - Larry D. Sanford
- Department of Radiation Oncology, Eastern Virginia Medical School
| | - Angela J. Kubik
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute
| | - Michael D. Delp
- Department of Nutrition, Food and Exercise Sciences, Florida State University
| | - Xiao Wen Mao
- Division of Biomedical Engineering Sciences (BMES), Department of Basic Sciences, Loma Linda University
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7
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Hansen AB, Lawley JS, Rickards CA, Howden EJ, Sarma S, Cornwell WK, Amin SB, Mugele H, Marume K, Possnig C, Whitworth LA, Williams MA, Levine BD. Reducing intracranial pressure by reducing central venous pressure: assessment of potential countermeasures to spaceflight-associated neuro-ocular syndrome. J Appl Physiol (1985) 2020; 130:283-289. [PMID: 33270516 DOI: 10.1152/japplphysiol.00786.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Spaceflight-associated neuro-ocular syndrome (SANS) involves unilateral or bilateral optic disc edema, widening of the optic nerve sheath, and posterior globe flattening. Owing to posterior globe flattening, it is hypothesized that microgravity causes a disproportionate change in intracranial pressure (ICP) relative to intraocular pressure. Countermeasures capable of reducing ICP include thigh cuffs and breathing against inspiratory resistance. Owing to the coupling of central venous pressure (CVP) and intracranial pressure, we hypothesized that both ICP and CVP will be reduced during both countermeasures. In four male participants (32 ± 13 yr) who were previously implanted with Ommaya reservoirs for treatment of unrelated clinical conditions, ICP was measured invasively through these ports. Subjects were healthy at the time of testing. CVP was measured invasively by a peripherally inserted central catheter. Participants breathed through an impedance threshold device (ITD, -7 cmH2O) to generate negative intrathoracic pressure for 5 min, and subsequently, wore bilateral thigh cuffs inflated to 30 mmHg for 2 min. Breathing through an ITD reduced both CVP (6 ± 2 vs. 3 ± 1 mmHg; P = 0.02) and ICP (16 ± 3 vs. 12 ± 1 mmHg; P = 0.04) compared to baseline, a result that was not observed during the free breathing condition (CVP, 6 ± 2 vs. 6 ± 2 mmHg, P = 0.87; ICP, 15 ± 3 vs. 15 ± 4 mmHg, P = 0.68). Inflation of the thigh cuffs to 30 mmHg caused no meaningful reduction in CVP in all four individuals (5 ± 4 vs. 5 ± 4 mmHg; P = 0.1), coincident with minimal reduction in ICP (15 ± 3 vs. 14 ± 4 mmHg; P = 0.13). The application of inspiratory resistance breathing resulted in reductions in both ICP and CVP, likely due to intrathoracic unloading.NEW & NOTEWORTHY Spaceflight causes pathological changes in the eye that may be due to the absence of gravitational unloading of intracranial pressure (ICP) under microgravity conditions commonly referred to as spaceflight-associated neuro-ocular syndrome (SANS), whereby countermeasures aimed at lowering ICP are necessary. These data show that impedance threshold breathing acutely reduces ICP via a reduction in central venous pressure (CVP). Whereas, acute thigh cuff inflation, a popular known spaceflight-associated countermeasure, had little effect on ICP and CVP.
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Affiliation(s)
- Alexander B Hansen
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Justin S Lawley
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria.,Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.,University of Texas Southwestern Medical Center, Dallas, Texas
| | - Caroline A Rickards
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, Texas
| | - Erin J Howden
- The Baker Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | - Satyam Sarma
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.,University of Texas Southwestern Medical Center, Dallas, Texas
| | - William K Cornwell
- Division of Cardiology, Department of Internal Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado
| | - Sachin B Amin
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Hendrik Mugele
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Kyohei Marume
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Carmen Possnig
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | | | - Michael A Williams
- Departments of Neurology and Neurological Surgery, University of Washington School of Medicine, Seattle, Washington
| | - Benjamin D Levine
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.,University of Texas Southwestern Medical Center, Dallas, Texas
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8
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Berdahl JP, Ferguson TJ, Samuelson TW. Periodic normalization of the translaminar pressure gradient prevents glaucomatous damage. Med Hypotheses 2020; 144:110258. [PMID: 33254565 DOI: 10.1016/j.mehy.2020.110258] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 08/30/2020] [Accepted: 09/05/2020] [Indexed: 01/02/2023]
Abstract
The 24-hour intraocular pressure (IOP) rhythm is of interest to clinicians but its overall impact on glaucomatous progression remains unclear. Recent evidence has implicated the translaminar pressure gradient (TLPG), or imbalance between IOP and intracranial pressure, in the development of glaucoma. Evidence suggests that retinal ganglion cell death occurs as a result of decreased axonal transport only after a sustained, elevated TLPG. We hypothesize that periodic normalization of the TLPG prevents glaucomatous damage by enabling temporary resumption of axonal transport. Temporary resumption of axonal transport allows for delivery of critical metabolic cargoes with concomitant removal of metabolic waste which prevents apoptosis of the retinal ganglion cell.
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9
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Lawley JS, Babu G, Janssen SLJE, Petersen LG, Hearon CM, Dias KA, Sarma S, Williams MA, Whitworth LA, Levine BD. Daily generation of a footward fluid shift attenuates ocular changes associated with head-down tilt bed rest. J Appl Physiol (1985) 2020; 129:1220-1231. [PMID: 32940563 DOI: 10.1152/japplphysiol.00250.2020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Astronauts have presented with a constellation of visual changes referred to as spaceflight-associated neuro-ocular syndrome (SANS). However, neither have early markers of microgravity-induced optic remodeling been fully identified nor have countermeasures been developed. To identify early markers of SANS, we studied 10 subjects with optical coherence tomography and ultrasonography when upright and supine and again after 24 h of 6° head-down tilt (HDT) bed rest. Upon acute transition from the upright to the supine position, choroid area (2.24 ± 0.53 to 2.28 ± 0.52 mm2, P = 0.001) and volume (9.51 ± 2.08 to 9.73 ± 2.08 mm3, P = 0.002) increased. After 24 h of HDT bed rest, subfoveal choroidal thickness (372 ± 93 to 381 ± 95 µm, P = 0.02), choroid area (2.25 ± 0.52 to 2.33 ± 0.54 mm2, P = 0.08), and volume (9.64 ± 2.03 to 9.82 ± 2.08 mm3, P = 0.08) increased relative to the supine position. Subsequently, seven subjects spent 3 days in -6°HDT bed rest to assess whether low-level lower body negative pressure (LBNP) could prevent the observed choroidal engorgement during bed rest. Maintaining the -6° HDT position for 3 days caused choroid area (Δ0.11 mm2, P = 0.05) and volume (Δ0.45 mm3, P = 0.003) to increase. When participants also spent 8 h daily under -20 mmHg LBNP, choroid volume still increased, but substantially (40%) less than in the control trial (Δ0.27 mm3, P = 0.05). Moreover, the increase in choroid area was diminished (Δ0.03 mm2, P = 0.13), indicating that low-level LBNP attenuates the choroid expansion associated with 3 days of -6° HDT bed rest. These data suggest that low-level LBNP may be an effective countermeasure for SANS.NEW & NOTEWORTHY Choroid measurements appear to be sensitive to changes in gravitational gradients, as well as periods of head-down tilt (HDT) bed rest, suggesting that they are potential indicators of early ocular remodeling and could serve to evaluate the efficacy of countermeasures for SANS. Eight hours of lower body negative pressure (LBNP) daily attenuates the choroid expansion associated with 3 days of strict -6° HDT bed rest, indicating that LBNP may be an effective countermeasure for SANS.
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Affiliation(s)
- Justin S Lawley
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.,University of Texas Southwestern Medical Center, Dallas, Texas.,Division of Physiology, Department of Sports Science, University of Innsbruck, Innsbruck, Austria
| | - Gautam Babu
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.,University of Texas Southwestern Medical Center, Dallas, Texas
| | | | - Lonnie G Petersen
- Department of Orthopedic Surgery, University of California San Diego, California
| | - Christopher M Hearon
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.,University of Texas Southwestern Medical Center, Dallas, Texas
| | - Katrin A Dias
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.,University of Texas Southwestern Medical Center, Dallas, Texas
| | - Satyam Sarma
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.,University of Texas Southwestern Medical Center, Dallas, Texas
| | - Michael A Williams
- Department of Neurology, University of Washington School of Medicine, Seattle, Washington.,Department of Neurological Surgery, University of Washington School of Medicine, Seattle, Washington
| | | | - Benjamin D Levine
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.,University of Texas Southwestern Medical Center, Dallas, Texas
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10
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Andersen MS, Pedersen CB, Poulsen FR. A new novel method for assessing intracranial pressure using non-invasive fundus images: a pilot study. Sci Rep 2020; 10:13062. [PMID: 32747697 PMCID: PMC7400759 DOI: 10.1038/s41598-020-70084-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 06/25/2020] [Indexed: 12/22/2022] Open
Abstract
Arteriole and venule diameter ratio (A/V-ratio) can be measured using fundus photography. In this pilot study, we correlated changes in the intracranial pressure with the diameter of vessels of the retina. We investigated whether increased intracranial pressure (ICP) was reflected in a measurable and quantifiable distention of the venule diameter, leading to a decreased A/V-ratio. This was demonstrated by assessment of the A/V-ratio in patients already undergoing conventional ICP monitoring with a cerebral intraparenchymal pressure monitor. Our method shows a correlation between A/V ratio and ICP and suggests an easily obtainable and usable point-of-care (POC), non-invasive method to estimate the intracranial pressure without the necessity of mydriatic drugs. Furthermore, the sensitivity/specificity analysis with a cut-off of < 0.8015 A/V-ratio, showed a sensitivity of 94% [85-98%] and a specificity of 50% [34-66%] with a positive likelihood ratio of 9.0. This means that in a clinical setting there is a 94% chance of correctly identifying individuals with ICP ≥ 20 mmHg.
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Affiliation(s)
- Mikkel Schou Andersen
- Department of Neurosurgery, Odense University Hospital, 5000, Odense, Denmark. .,Clinical Institute, University of Southern Denmark, Odense, Denmark. .,BRIDGE (Brain Research - Inter Disciplinary Guided Excellence), University of Southern Denmark, Odense, Denmark.
| | - Christian Bonde Pedersen
- Department of Neurosurgery, Odense University Hospital, 5000, Odense, Denmark.,Clinical Institute, University of Southern Denmark, Odense, Denmark.,BRIDGE (Brain Research - Inter Disciplinary Guided Excellence), University of Southern Denmark, Odense, Denmark
| | - Frantz Rom Poulsen
- Department of Neurosurgery, Odense University Hospital, 5000, Odense, Denmark.,Clinical Institute, University of Southern Denmark, Odense, Denmark.,BRIDGE (Brain Research - Inter Disciplinary Guided Excellence), University of Southern Denmark, Odense, Denmark
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11
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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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12
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Zhao Z, Yu X, Yang X, Zhang J, Zhang D, Sun N, Fan Z. Elevated intraocular pressure causes cellular and molecular retinal injuries, advocating a more moderate intraocular pressure setting during phacoemulsification surgery. Int Ophthalmol 2020; 40:3323-3336. [PMID: 32725401 DOI: 10.1007/s10792-020-01519-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2020] [Accepted: 07/17/2020] [Indexed: 01/04/2023]
Abstract
PURPOSE To evaluate the cellular and molecular retinal injuries induced by various intraocular pressure (IOP) settings in a mouse model of acute ocular hypertension (AOH), and to advise using a more moderate target IOP during phacoemulsification (phaco) surgery. METHODS A mouse model of AOH that mimics a transient IOP elevation during phacoemulsification cataract surgery was established. Six groups with various settings of target IOP were included. Retinal tissues were assessed with terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate nick end-labeling (TUNEL) staining for neuron loss, immunofluorescence with Iba1 for microglia activation, and quantitative real-time polymerase chain reaction analysis with tight junction proteins (claudin-3 and claudin-5) or classic inflammation markers (IL-1β and eNOS) for impairment of the blood-retinal barrier (BRB) and inflammatory injury. RESULTS Compared with those in the 45-mmHg IOP group, significantly increased number of neurons loss and increased microglia activation were observed in 90-mmHg IOP group. In addition, the expression of claudin-3 and claudin-5 was significantly decreased, while the expression of IL1-β and eNOS was up-regulated, indicating impairment of the BRB and inflammatory injury in the retina. Furthermore, these findings of neuron loss, microglia activation, and inflammation in the 90-mmHg groups were exacerbated when an IOP-induced retinal injury was established 5 days earlier, while those in the 45-mmHg groups remained almost unchanged. CONCLUSIONS In conclusion, these results showed that a relatively commonly used high IOP setting (90 mmHg) could induce significantly more serious retinal injury. An IOP setting around 45 mmHg is relatively safe and might be recommended in phaco surgery, especially in patients with advanced glaucoma, previous acute angle closure crisis, or other diseases with fragile retina and optic nerve.
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Affiliation(s)
- Zhenni Zhao
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Jinsui Road NO.7, Guangzhou, 510060, Guangdong, China
| | - Xiaowei Yu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Jinsui Road NO.7, Guangzhou, 510060, Guangdong, China
| | - Xue Yang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Jinsui Road NO.7, Guangzhou, 510060, Guangdong, China
| | - Jiamin Zhang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Jinsui Road NO.7, Guangzhou, 510060, Guangdong, China
| | - Dandan Zhang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Jinsui Road NO.7, Guangzhou, 510060, Guangdong, China
| | - Nannan Sun
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Jinsui Road NO.7, Guangzhou, 510060, Guangdong, China.
| | - Zhigang Fan
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Jinsui Road NO.7, Guangzhou, 510060, Guangdong, China.
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13
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Long-term follow-up of optic neuropathy in chronic low cerebrospinal fluid pressure monkeys: the Beijing Intracranial and Intraocular Pressure (iCOP) Study. SCIENCE CHINA-LIFE SCIENCES 2020; 63:1762-1765. [PMID: 32567001 DOI: 10.1007/s11427-018-1626-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 12/20/2019] [Indexed: 10/24/2022]
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14
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Zhao D, He Z, Wang L, Fortune B, Lim JKH, Wong VHY, Nguyen CTO, Bui BV. Response of the Trilaminar Retinal Vessel Network to Intraocular Pressure Elevation in Rat Eyes. Invest Ophthalmol Vis Sci 2020; 61:2. [PMID: 32031574 PMCID: PMC7325622 DOI: 10.1167/iovs.61.2.2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Purpose The purpose of this study was to test the hypothesis that the superficial, intermediate, and deep retinal vascular plexus show different responses to intraocular pressure (IOP) elevation. Methods Anesthetized adult Long Evans rats (n = 14) were imaged using optical coherence tomography angiography (OCTA; Spectralis) at baseline (IOP 10 mm Hg) and in follow-up mode to examine the vasculature during IOP elevation (10 to 110 mm Hg, 10 mm Hg steps, each step 3 minutes). A 20° × 10° field was imaged. Vessel density within a 2D projection image was determined (%) for the superficial vascular complex (SVC), intermediate capillary plexus (ICP), and deep capillary plexus (DCP). Comparisons were made between layers using 2-way repeated measures ANOVA (layer versus IOP) following normalization to baseline (% relative to 10 mm Hg). Results The three vascular layers responded differently to IOP elevation. For IOPs between 40 and 60 mm Hg, DCP and ICP capillaries were significantly more resistant to IOP elevation than those in the SVC. When IOP was elevated above 70 mm Hg, all layers showed reduced vessel density. IOP induced change in SVC vessel density closely followed reductions in thickness of the inner retinal layers (nerve fiber, ganglion cell, and inner plexiform layer). This close relationship between reductions in tissue thickness and vessel density was less apparent for the ICP and DCP. Conclusions These data show that the intermediate and deep vascular plexus in the rat retina have a greater capacity for autoregulation against mild IOP elevation but are more affected at high IOP.
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15
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Zhao D, Wong VHY, Nguyen CTO, Jobling AI, Fletcher EL, Vingrys AJ, Bui BV. Reversibility of Retinal Ganglion Cell Dysfunction From Chronic IOP Elevation. Invest Ophthalmol Vis Sci 2020; 60:3878-3886. [PMID: 31529082 DOI: 10.1167/iovs.19-27113] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To test the hypothesis that the capacity for retinal ganglion cells to functionally recover from chronic IOP elevation is dependent on the duration of IOP elevation. Methods IOP elevation was induced in one eye in anesthetized (isoflurane) adult C57BL6/J mice using a circumlimbal suture. Sutures were left in place for 8 and 16 weeks (n = 30 and 28). In two other groups the suture was cut after 8 and 12 weeks (n = 30 and 28), and ganglion cell function (electroretinography) and retinal structure (optical coherence tomography) were assessed 4 weeks later. Ganglion cell density was quantified by counting RBPMS (RNA-binding protein with multiple splicing)-stained cells. Results With IOP elevation (∼10 mm Hg above baseline), ganglion cell function declined to 75% ± 8% at 8 weeks and 59% ± 4% at 16 weeks relative to contralateral control eyes. The retinal nerve fiber layer was thinner at 8 (84% ± 4%) and 16 weeks (83% ± 3%), without a significant difference in total retinal thickness. Ganglion cell function recovered with IOP normalization (suture removal) at week 8 (97% ± 7%), but not at week 12 (73% ± 6%). Ganglion cell loss was found in all groups (-8% to -13%). Conclusions In the mouse circumlimbal suture model, 12 weeks of IOP elevation resulted in irreversible ganglion cell dysfunction, whereas retinal dysfunction was fully reversible after 8 weeks of IOP elevation.
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Affiliation(s)
- Da Zhao
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Victoria, Australia
| | - Vickie H Y Wong
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Victoria, Australia
| | - Christine T O Nguyen
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Victoria, Australia
| | - Andrew I Jobling
- Department of Anatomy and Neuroscience, University of Melbourne, Parkville, Victoria, Australia
| | - Erica L Fletcher
- Department of Anatomy and Neuroscience, University of Melbourne, Parkville, Victoria, Australia
| | - Algis J Vingrys
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Victoria, Australia
| | - Bang V Bui
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Victoria, Australia
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16
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Ficarrotta KR, Passaglia CL. Intracranial pressure modulates aqueous humour dynamics of the eye. J Physiol 2020; 598:403-413. [PMID: 31769030 DOI: 10.1113/jp278768] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Accepted: 11/22/2019] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS An elevation in intracranial pressure (ICP) lowers conventional outflow facility (increases aqueous outflow resistance) of rat eyes. The reduction in outflow facility correlates with an increase in intraocular pressure (IOP). The effect of ICP elevation on outflow facility and IOP is blocked by TTX. The results indicate that aqueous humour dynamics is modulated by ICP-driven neural feedback from the brain. This feedback mechanism may act to stabilize translaminar pressure across the optic nerve head and may provide a new avenue for glaucoma therapy. ABSTRACT While intraocular pressure (IOP) is a well-known risk factor for glaucoma, intracranial pressure (ICP) is attracting heightened interest because of its influence on optic nerve head biomechanics. Studies have shown that ICP can have marked impacts on posterior eye health by modifying the translaminar pressure gradient across the optic nerve. There is also growing evidence that IOP and ICP may be interconnected, although the mechanism of their putative interaction is unknown. We sought to test the hypothesis that ICP modulates IOP by altering aqueous humour dynamics. The anterior chamber and lateral ventricle of anaesthetized Brown-Norway rats were cannulated with fine-gauge needles connected to a programmable pump and saline reservoir, respectively. ICP was manipulated by varying reservoir height, and eye outflow facility (C) was determined from the pump flow rate required to hold IOP at different levels. C was 22 ± 4 nl/min/mmHg at resting ICP and 13 ± 3 nl/min/mmHg when ICP was raised 15 mmHg, a reduction of 41 ± 13% (n = 18). The decrease in outflow facility was independent of blood pressure, reversible, scaled with ICP elevation and correlated with increases in resting IOP. It was physiological in origin because C returned to baseline values after the rats were killed and corneal application of TTX though ICP remained elevated. These results indicate that a neural feedback mechanism driven by ICP regulates conventional outflow facility in rats. The mechanism may protect the eye from translaminar pressure swings and may offer a new target for glaucoma treatment.
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Affiliation(s)
- Kayla R Ficarrotta
- Medical Engineering Department, University of South Florida, Tampa, FL, 33620, USA
| | - Christopher L Passaglia
- Medical Engineering Department, University of South Florida, Tampa, FL, 33620, USA.,Ophthalmology Department, University of South Florida, Tampa, FL, 33620, USA
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17
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Baneke AJ, Aubry J, Viswanathan AC, Plant GT. The role of intracranial pressure in glaucoma and therapeutic implications. Eye (Lond) 2020; 34:178-191. [PMID: 31776450 PMCID: PMC7002772 DOI: 10.1038/s41433-019-0681-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Accepted: 10/21/2019] [Indexed: 11/09/2022] Open
Abstract
Despite glaucoma being the second leading cause of blindness globally, its pathogenesis remains incompletely understood. Although intraocular pressure (IOP) contributes to glaucoma, and reducing IOP slows progress of the disease, some patients progress despite normal IOP (NTG). Glaucomatous damage causes characteristic cupping of the optic nerve where it passes through the lamina cribrosa. There is evidence that cerebrospinal fluid (CSF) within the optic nerve sheath has a different composition from CSF surrounding the brain. Furthermore, fluctuations in CSF flow into the optic nerve sheath may be reduced by trabeculae within the sheath, and on standing intracranial pressure (ICP) within the sheath is stabilised at around 3 mmHg due to orbital pressure. Blood pressure has been linked both to glaucoma and ICP. These facts have led some to conclude that ICP does not play a role in glaucoma. However, according to stress formulae and Laplace's Law, stress within the lamina cribrosa is dependent on the forces on either side of it, (IOP and ICP), and its thickness. On lying flat at night, ICP between the brain and optic nerve sheath should equalise. Most evidence suggests ICP is lower in glaucoma than in control groups, and that the lamina cribrosa is thinner and more posteriorly displaced in glaucoma. Subjects who have had ICP reduced have developed signs of glaucoma. This review finds most evidence supports a role for low ICP in the pathogenesis of glaucoma. Caffeine, theophylline and vitamin A may increase ICP, and could be new candidates for an oral treatment.
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Affiliation(s)
- Alex J Baneke
- Moorfields Eye Hospital NHS Foundation Trust, London, UK.
| | - James Aubry
- General Electric Oil and Gas, Florence, Italy
| | - Ananth C Viswanathan
- NIHR Biomedical Research Centre for Ophthalmology at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK
| | - Gordon T Plant
- Institute of Neurology, University College London, London, UK
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18
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宋 红, 李 琦, 王 宁, 王 文, 龙 晓, 刘 志. [Review of studies on the application of biomechanical factors in the evaluation of glaucoma]. SHENG WU YI XUE GONG CHENG XUE ZA ZHI = JOURNAL OF BIOMEDICAL ENGINEERING = SHENGWU YIXUE GONGCHENGXUE ZAZHI 2019; 36:315-319. [PMID: 31016950 PMCID: PMC9929904 DOI: 10.7507/1001-5515.201809058] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Indexed: 11/03/2022]
Abstract
There are so many biomechanical risk factors related with glaucoma and their relationship is much complex. This paper reviewed the state-of-the-art research works on glaucoma related mechanical effects. With regards to the development perspectives of studies on glaucoma biomechanics, a completely novel biomechanical evaluation factor -- Fractional Flow Reserve (FPR) for glaucoma was proposed, and developing clinical application oriented glaucoma risk assessment algorithm and application system by using the new techniques such as artificial intelligence and machine learning were suggested.
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Affiliation(s)
- 红芳 宋
- 临床生物力学应用基础研究北京市重点实验室(北京 100069)Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Beijing 100069, P.R.China
- 首都医科大学 生物医学工程学院(北京 100069)School of Biomedical Engineering, Capital Medical University, Beijing 100069, P.R.China
| | - 琦 李
- 临床生物力学应用基础研究北京市重点实验室(北京 100069)Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Beijing 100069, P.R.China
- 首都医科大学 生物医学工程学院(北京 100069)School of Biomedical Engineering, Capital Medical University, Beijing 100069, P.R.China
| | - 宁利 王
- 临床生物力学应用基础研究北京市重点实验室(北京 100069)Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Beijing 100069, P.R.China
| | - 文佳 王
- 临床生物力学应用基础研究北京市重点实验室(北京 100069)Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Beijing 100069, P.R.China
- 首都医科大学 生物医学工程学院(北京 100069)School of Biomedical Engineering, Capital Medical University, Beijing 100069, P.R.China
| | - 晓雪 龙
- 临床生物力学应用基础研究北京市重点实验室(北京 100069)Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Beijing 100069, P.R.China
- 首都医科大学 生物医学工程学院(北京 100069)School of Biomedical Engineering, Capital Medical University, Beijing 100069, P.R.China
| | - 志成 刘
- 临床生物力学应用基础研究北京市重点实验室(北京 100069)Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Beijing 100069, P.R.China
- 首都医科大学 生物医学工程学院(北京 100069)School of Biomedical Engineering, Capital Medical University, Beijing 100069, P.R.China
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19
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Li XX, Zhang Z, Zeng HY, Wu S, Liu L, Zhang JX, Liu Q, Yang DY, Wang NL. Selective Early Glial Reactivity in the Visual Pathway Precedes Axonal Loss, Following Short-Term Cerebrospinal Fluid Pressure Reduction. Invest Ophthalmol Vis Sci 2019; 59:3394-3404. [PMID: 30025070 DOI: 10.1167/iovs.17-22232] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To examine the early glial reactivity and neuron damage in response to short-term cerebrospinal fluid pressure (CSFp) reduction, as compared with intraocular pressure (IOP) elevation. Methods The experiment included 54 male Sprague-Dawley rats with elevated translaminar cribrosa pressure difference (TLPD), defined as IOP minus CSFp. These rats underwent either continuous CSF drainage for 6 hours (n = 18), or unilateral IOP elevation to 40 mm Hg for 6 hours (n = 18). For control, 18 normal rats were anesthetized for 6 hours. Orthograde axonal transport was examined by intravitreal injection of 3% rhodamine-β-isothiocyanate. We also used transmission electron microscopy to display the ultrastructural features of retinal ganglion cell axons in the optic nerve head. Early glial reactivity in the retina, lateral geniculate nucleus (LGN), and superior colliculus (SC) was detected by immunostaining and Western blot for the glial fibrillary acidic protein (GFAP) and glutamine synthetase (GS). We also observed the glial reactivity in the inferior colliculus and hippocampus to rule out possible influences of CSF dynamics and composition. Results Anterograde staining with 3% rhodamine-β-isothiocyanate revealed decreased fluorescence intensity of the SC and LGN projected from both lower CSFp and higher IOP eyes. Transmission electron microscopy showed loss of axons from the optic nerve head in the high-IOP group, but not in the low-CSFp group. Compared with the anesthesia control group, GFAP expression was significantly increased in the retina, LGN, and SC, whereas GS expression was only increased in the retina following CSFp reduction. However, their expressions were not significantly elevated in the inferior colliculus and hippocampus. In the high-IOP group, expressions of GFAP and GS were significantly increased in the retina, LGN, and SC. Conclusions Visual system neurons may be much more sensitive than other nervous tissues. Following short-term CSFp reduction, early glial reactivity may precede axonal loss. Changes of translaminar cribrosa pressure difference in both experimental low-CSFp and high-IOP groups induce selective early glial reactivity. The neuron damage from abnormally low CSFp may be pathogenetically similar to high IOP.
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Affiliation(s)
- Xiao Xia Li
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China.,Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, China.,Beijing Institute of Ophthalmology, Beijing, China
| | - Zheng Zhang
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China.,Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, China
| | - Hui Yang Zeng
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China.,Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, China.,Beijing Institute of Ophthalmology, Beijing, China
| | - Shen Wu
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China.,Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, China.,Beijing Institute of Ophthalmology, Beijing, China
| | - Lu Liu
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China.,Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, China.,Beijing Institute of Ophthalmology, Beijing, China
| | - Jing Xue Zhang
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China.,Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, China.,Beijing Institute of Ophthalmology, Beijing, China
| | - Qian Liu
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China.,Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, China.,Beijing Institute of Ophthalmology, Beijing, China
| | - Di Ya Yang
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China.,Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, China
| | - Ning Li Wang
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China.,Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, China.,Beijing Institute of Ophthalmology, Beijing, China
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20
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Mao XW, Boerma M, Rodriguez D, Campbell-Beachler M, Jones T, Stanbouly S, Sridharan V, Nishiyama NC, Wroe A, Nelson GA. Combined Effects of Low-Dose Proton Radiation and Simulated Microgravity on the Mouse Retina and the Hematopoietic System. Radiat Res 2018; 192:241-250. [PMID: 30430917 DOI: 10.1667/rr15219.1] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The purpose of the current study was to characterize the effects of simulated microgravity and radiation-induced changes in retina and retinal vasculature, and to assess the accompanying early changes in immune cells and hematological parameters. To better understand the effects of spaceflight, we used a combination of treatments designed to simulate both the radiation and low-gravity aspects of space conditions. To simulate the broad energy spectrum of a large solar particle event (SPE) and galactic cosmic ray (GCR) radiation, male C57BL/6J mice were exposed to whole-body irradiation using fully modulated beams of 150-MeV protons containing particles of energy from 0 to 150 MeV and a uniform dose-vs.-depth profile. The mice were also hindlimb-unloaded (HLU) by tail suspension. Mice were unloaded for 7 days, exposed to 50 cGy, unloaded for an additional 7 days and then sacrificed for tissue isolation at days 4 and 30 after the combined treatments. Increases in the number of apoptotic cells were observed in the endothelial cells of mice that received radiation alone or with HLU compared to controls at both days 4 and 30 (P < 0.05). Endothelial nitric oxide synthase (eNOS) levels were significantly elevated in the retina after irradiation only or combined with HLU compared to controls at the 30-day time point (P < 0.05). The most robust changes were observed in the combination group, suggesting a synergistic response to radiation and unloading. For hematopoietic parameters, our analysis indicated the main effects for time and radiation at day 4 after treatments (day 11 postirradiation) (P < 0.05), but a smaller influence of HLU for both white blood cell and lymphocyte counts. The group treated with both radiation and HLU showed greater than 50% reduction in lymphocyte counts compared to controls. Radiation-dependent differences were also noted in specific lymphocyte subpopulations (T, B, natural killer cells). This study shows indications of an early effect of low-dose radiation and spaceflight conditions on retina and immune populations.
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Affiliation(s)
- X W Mao
- Department of Basic Sciences, Division of Radiation Research, Loma Linda University School of Medicine and Medical Center, Loma Linda, California
| | - M Boerma
- Division of Radiation Health, Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - D Rodriguez
- Department of Basic Sciences, Division of Radiation Research, Loma Linda University School of Medicine and Medical Center, Loma Linda, California
| | - M Campbell-Beachler
- Department of Basic Sciences, Division of Radiation Research, Loma Linda University School of Medicine and Medical Center, Loma Linda, California
| | - T Jones
- Department of Basic Sciences, Division of Radiation Research, Loma Linda University School of Medicine and Medical Center, Loma Linda, California
| | - S Stanbouly
- Department of Basic Sciences, Division of Radiation Research, Loma Linda University School of Medicine and Medical Center, Loma Linda, California
| | - V Sridharan
- Division of Radiation Health, Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - N C Nishiyama
- Department of Basic Sciences, Division of Radiation Research, Loma Linda University School of Medicine and Medical Center, Loma Linda, California
| | - A Wroe
- Department of Radiation Medicine, Loma Linda University School of Medicine and Medical Center, Loma Linda, California
| | - G A Nelson
- Department of Basic Sciences, Division of Radiation Research, Loma Linda University School of Medicine and Medical Center, Loma Linda, California
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21
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Liu L, Li X, Killer HE, Cao K, Li J, Wang N. Changes in retinal and choroidal morphology after cerebrospinal fluid pressure reduction: a Beijing iCOP study. SCIENCE CHINA-LIFE SCIENCES 2018; 62:268-271. [PMID: 30229377 DOI: 10.1007/s11427-018-9332-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 05/01/2018] [Indexed: 10/28/2022]
Affiliation(s)
- Lu Liu
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, 100730, China.,Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, 100730, China.,Beijing institute of Ophthalmology, Beijing, 100730, China
| | - Xiaoxia Li
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, 100730, China.,Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, 100730, China.,Beijing institute of Ophthalmology, Beijing, 100730, China
| | - Hanspeter E Killer
- Department of Ophthalmology, Kantonsspital Aarau, Aarau, CH-5001, Switzerland.,Eye Institute, University of Basel, Aarau, CH-5001, Switzerland
| | - Kai Cao
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, 100730, China.,Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, 100730, China.,Beijing institute of Ophthalmology, Beijing, 100730, China
| | - Jing Li
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, 100730, China.,Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, 100730, China.,Beijing institute of Ophthalmology, Beijing, 100730, China
| | - Ningli Wang
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, 100730, China. .,Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, 100730, China. .,Beijing institute of Ophthalmology, Beijing, 100730, China.
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22
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Esler TB, Maturana MI, Kerr RR, Grayden DB, Burkitt AN, Meffin H. Biophysical basis of the linear electrical receptive fields of retinal ganglion cells. J Neural Eng 2018; 15:055001. [PMID: 29889051 DOI: 10.1088/1741-2552/aacbaa] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Responses of retinal ganglion cells to direct electrical stimulation have been shown experimentally to be well described by linear-nonlinear models. These models rely on the simplifying assumption that retinal ganglion cell responses to stimulation with an array of electrodes are driven by a simple linear weighted sum of stimulus current amplitudes from each electrode, known as the 'electrical receptive field'. OBJECTIVE This paper aims to demonstrate the biophysical basis of the linear-nonlinear model and the electrical receptive field to facilitate the development of improved stimulation strategies for retinal implants. APPROACH We compare the linear-nonlinear model of subretinal electrical stimulation with a multi-layered, biophysical, volume conductor model of retinal stimulation. MAIN RESULTS Our results show that the linear electrical receptive field of the linear-nonlinear model matches the transmembrane currents induced by electrodes (the activating function) at the site of the high-density sodium channel band with only minor discrepancies. The discrepancies are mostly eliminated by including axial current flow originating from adjacent cell compartments. Furthermore, for cells where a single linear electrical receptive field is insufficient, we show that cell responses are likely driven by multiple sites of action potential initiation with multiple distinct receptive fields, each of which can be accurately described by the activating function. SIGNIFICANCE This result establishes that the biophysical basis of the electrical receptive field of the linear-nonlinear model is the superposition of transmembrane currents induced by different electrodes at and near the site of action potential initiation. Together with existing experimental support for linear-nonlinear models of electrical stimulation, this provides a firm basis for using this much simplified model to generate more optimal stimulation patterns for retinal implants.
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Affiliation(s)
- Timothy B Esler
- NeuroEngineering Laboratory, Department of Biomedical Engineering, The University of Melbourne, Australia
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23
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Tan B, MacLellan B, Mason E, Bizheva K. Structural, functional and blood perfusion changes in the rat retina associated with elevated intraocular pressure, measured simultaneously with a combined OCT+ERG system. PLoS One 2018; 13:e0193592. [PMID: 29509807 PMCID: PMC5839563 DOI: 10.1371/journal.pone.0193592] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Accepted: 02/14/2018] [Indexed: 02/07/2023] Open
Abstract
Acute elevation of intraocular pressure (IOP) to ischemic and non-ischemic levels can cause temporary or permanent changes in the retinal morphology, function and blood flow/blood perfusion. Previously, such changes in the retina were assessed separately with different methods in clinical studies and animal models. In this study, we used a combined OCT+ ERG system in combination with Doppler OCT and OCT angiography (OCTA) imaging protocols, in order to evaluate simultaneously and correlate changes in the retinal morphology, the retinal functional response to visual stimulation, and the retinal blood flow/blood perfusion, associated with IOP elevation to ischemic and non-ischemic levels in rats. Results from this study suggest that the inner retina responds faster to IOP elevation to levels greater than 30 mmHg with significant reduction of the total retinal blood flow (TRBF), decrease of the capillaries’ perfusion and reduction of the ON bipolar cells contribution to the ERG traces. Furthermore, this study showed that ischemic levels of IOP elevation cause an additional significant decrease in the ERG photoreceptor response in the posterior retina. Thirty minutes after IOP normalization, retinal morphology, blood flow and blood perfusion recovered to baseline values, while retinal function did not recover completely.
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Affiliation(s)
- Bingyao Tan
- Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, Canada
| | - Benjamin MacLellan
- Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, Canada
| | - Erik Mason
- Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, Canada
| | - Kostadinka Bizheva
- Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, Canada
- School of Optometry and Vision Science, University of Waterloo, Waterloo, Ontario, Canada
- Department of System Design Engineering, University of Waterloo, Waterloo, Ontario, Canada
- * E-mail:
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24
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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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25
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Shen G, Link S, Kumar S, Nusbaum DM, Tse DY, Fu Y, Wu SM, Frankfort BJ. Characterization of Retinal Ganglion Cell and Optic Nerve Phenotypes Caused by Sustained Intracranial Pressure Elevation in Mice. Sci Rep 2018; 8:2856. [PMID: 29434244 PMCID: PMC5809383 DOI: 10.1038/s41598-018-21254-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 01/31/2018] [Indexed: 12/16/2022] Open
Abstract
Elevated intracranial pressure (ICP) can result in multiple neurologic sequelae including vision loss. Inducible models of ICP elevation are lacking in model organisms, which limits our understanding of the mechanism by which increased ICP impacts the visual system. We adapted a mouse model for the sustained elevation of ICP and tested the hypothesis that elevated ICP impacts the optic nerve and retinal ganglion cells (RGCs). ICP was elevated and maintained for 2 weeks, and resulted in multiple anatomic changes that are consistent with human disease including papilledema, loss of physiologic cupping, and engorgement of the optic nerve head. Elevated ICP caused a loss of RGC somas in the retina and RGC axons within the optic nerve, as well as a reduction in both RGC electrical function and contrast sensitivity. Elevated ICP also caused increased hypoxia-inducible factor (HIF)-1 alpha expression in the ganglion cell layer. These experiments confirm that sustained ICP elevation can be achieved in mice and causes phenotypes that preferentially impact RGCs and are similar to those seen in human disease. With this model, it is possible to model human diseases of elevated ICP such as Idiopathic Intracranial Hypertension and Spaceflight Associated Neuro-ocular Syndrome.
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Affiliation(s)
- Guofu Shen
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX, USA
| | - Schuyler Link
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX, USA
| | - Sandeep Kumar
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX, USA
| | - Derek M Nusbaum
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX, USA.,Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Dennis Y Tse
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX, USA.,School of Optometry, The Hong Kong Polytechnic University, Hong Kong, Hong Kong
| | - Yingbin Fu
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX, USA.,Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Samuel M Wu
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX, USA.,Department of Neuroscience, 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.
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26
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Nelson ES, Mulugeta L, Feola A, Raykin J, Myers JG, Samuels BC, Ethier CR. The impact of ocular hemodynamics and intracranial pressure on intraocular pressure during acute gravitational changes. J Appl Physiol (1985) 2017; 123:352-363. [PMID: 28495842 DOI: 10.1152/japplphysiol.00102.2017] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 05/04/2017] [Accepted: 05/04/2017] [Indexed: 11/22/2022] Open
Abstract
Exposure to microgravity causes a bulk fluid shift toward the head, with concomitant changes in blood volume/pressure, and intraocular pressure (IOP). These and other factors, such as intracranial pressure (ICP) changes, are suspected to be involved in the degradation of visual function and ocular anatomical changes exhibited by some astronauts. This is a significant health concern. Here, we describe a lumped-parameter numerical model to simulate volume/pressure alterations in the eye during gravitational changes. The model includes the effects of blood and aqueous humor dynamics, ICP, and IOP-dependent ocular compliance. It is formulated as a series of coupled differential equations and was validated against four existing data sets on parabolic flight, body inversion, and head-down tilt (HDT). The model accurately predicted acute IOP changes in parabolic flight and HDT, and was satisfactory for the more extreme case of inversion. The short-term response to the changing gravitational field was dominated by ocular blood pressures and compliance, while longer-term responses were more dependent on aqueous humor dynamics. ICP had a negligible effect on acute IOP changes. This relatively simple numerical model shows promising predictive capability. To extend the model to more chronic conditions, additional data on longer-term autoregulation of blood and aqueous humor dynamics are needed.NEW & NOTEWORTHY A significant percentage of astronauts present anatomical changes in the posterior eye tissues after spaceflight. Hypothesized increases in ocular blood volume and intracranial pressure (ICP) in space have been considered to be likely factors. In this work, we provide a novel numerical model of the eye that incorporates ocular hemodynamics, gravitational forces, and ICP changes. We find that changes in ocular hemodynamics govern the response of intraocular pressure during acute gravitational change.
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Affiliation(s)
- Emily S Nelson
- National Aeronautic and Space Administration, Glenn Research Center, Cleveland, Ohio
| | | | - Andrew Feola
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia; and
| | - Julia Raykin
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia; and
| | - Jerry G Myers
- National Aeronautic and Space Administration, Glenn Research Center, Cleveland, Ohio
| | - Brian C Samuels
- Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama
| | - C Ross Ethier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia; and
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27
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Tran H, Grimm J, Wang B, Smith MA, Gogola A, Nelson S, Tyler-Kabara E, Schuman J, Wollstein G, Sigal IA. Mapping in-vivo optic nerve head strains caused by intraocular and intracranial pressures. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2017; 10067. [PMID: 29618852 DOI: 10.1117/12.2257360] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Although it is well documented that abnormal levels of either intraocular (IOP) or intracranial pressure (ICP) can lead to potentially blinding conditions, such as glaucoma and papilledema, little is known about how the pressures actually affect the eye. Even less is known about potential interplay between their effects, namely how the level of one pressure might alter the effects of the other. Our goal was to measure in-vivo the pressure-induced stretch and compression of the lamina cribrosa due to acute changes of IOP and ICP. The lamina cribrosa is a structure within the optic nerve head, in the back of the eye. It is important because it is in the lamina cribrosa that the pressure-induced deformations are believed to initiate damage to neural tissues leading to blindness. An eye of a rhesus macaque monkey was imaged in-vivo with optical coherence tomography while IOP and ICP were controlled through cannulas in the anterior chamber and lateral ventricle, respectively. The image volumes were analyzed with a newly developed digital image correlation technique. The effects of both pressures were highly localized, nonlinear and non-monotonic, with strong interactions. Pressure variations from the baseline normal levels caused substantial stretch and compression of the neural tissues in the posterior pole, sometimes exceeding 20%. Chronic exposure to such high levels of biomechanical insult would likely lead to neural tissue damage and loss of vision. Our results demonstrate the power of digital image correlation technique based on non-invasive imaging technologies to help understand how pressures induce biomechanical insults and lead to vision problems.
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Affiliation(s)
- H Tran
- Department of Ophthalmology, University of Pittsburgh, 203 Lothrop St., Pittsburgh, PA, USA 15213.,Department of Bioengineering, University of Pittsburgh, 3700 O'Hara St., Pittsburgh, PA, USA 15213
| | - J Grimm
- Department of Ophthalmology, University of Pittsburgh, 203 Lothrop St., Pittsburgh, PA, USA 15213
| | - B Wang
- Department of Ophthalmology, University of Pittsburgh, 203 Lothrop St., Pittsburgh, PA, USA 15213.,Department of Bioengineering, University of Pittsburgh, 3700 O'Hara St., Pittsburgh, PA, USA 15213
| | - M A Smith
- Department of Ophthalmology, University of Pittsburgh, 203 Lothrop St., Pittsburgh, PA, USA 15213.,Department of Bioengineering, University of Pittsburgh, 3700 O'Hara St., Pittsburgh, PA, USA 15213
| | - A Gogola
- Department of Ophthalmology, University of Pittsburgh, 203 Lothrop St., Pittsburgh, PA, USA 15213
| | - S Nelson
- Department of Ophthalmology, University of Pittsburgh, 203 Lothrop St., Pittsburgh, PA, USA 15213
| | - E Tyler-Kabara
- Department of Neurosurgery, University of Pittsburgh, 200 Lothrop St, Pittsburgh PA, USA 15213
| | - J Schuman
- NYU Langone Eye Center, NYU School of Medicine, 240 East 38 St., New York, NY, USA 10016
| | - G Wollstein
- NYU Langone Eye Center, NYU School of Medicine, 240 East 38 St., New York, NY, USA 10016
| | - I A Sigal
- Department of Ophthalmology, University of Pittsburgh, 203 Lothrop St., Pittsburgh, PA, USA 15213.,Department of Bioengineering, University of Pittsburgh, 3700 O'Hara St., Pittsburgh, PA, USA 15213
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28
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Lawley JS, Petersen LG, Howden EJ, Sarma S, Cornwell WK, Zhang R, Whitworth LA, Williams MA, Levine BD. Effect of gravity and microgravity on intracranial pressure. J Physiol 2017; 595:2115-2127. [PMID: 28092926 DOI: 10.1113/jp273557] [Citation(s) in RCA: 160] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2016] [Accepted: 12/19/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Astronauts have recently been discovered to have impaired vision, with a presentation that resembles syndromes of elevated intracranial pressure on Earth. Gravity has a profound effect on fluid distribution and pressure within the human circulation. In contrast to prevailing theory, we observed that microgravity reduces central venous and intracranial pressure. This being said, intracranial pressure is not reduced to the levels observed in the 90 deg seated upright posture on Earth. Thus, over 24 h in zero gravity, pressure in the brain is slightly above that observed on Earth, which may explain remodelling of the eye in astronauts. ABSTRACT Astronauts have recently been discovered to have impaired vision, with a presentation that resembles syndromes of elevated intracranial pressure (ICP). This syndrome is considered the most mission-critical medical problem identified in the past decade of manned spaceflight. We recruited five men and three women who had an Ommaya reservoir inserted for the delivery of prophylactic CNS chemotherapy, but were free of their malignant disease for at least 1 year. ICP was assessed by placing a fluid-filled 25 gauge butterfly needle into the Ommaya reservoir. Subjects were studied in the upright and supine position, during acute zero gravity (parabolic flight) and prolonged simulated microgravity (6 deg head-down tilt bedrest). ICP was lower when seated in the 90 deg upright posture compared to lying supine (seated, 4 ± 1 vs. supine, 15 ± 2 mmHg). Whilst lying in the supine posture, central venous pressure (supine, 7 ± 3 vs. microgravity, 4 ± 2 mmHg) and ICP (supine, 17 ± 2 vs. microgravity, 13 ± 2 mmHg) were reduced in acute zero gravity, although not to the levels observed in the 90 deg seated upright posture on Earth. Prolonged periods of simulated microgravity did not cause progressive elevations in ICP (supine, 15 ± 2 vs. 24 h head-down tilt, 15 ± 4 mmHg). Complete removal of gravity does not pathologically elevate ICP but does prevent the normal lowering of ICP when upright. These findings suggest the human brain is protected by the daily circadian cycles in regional ICPs, without which pathology may occur.
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Affiliation(s)
- Justin S Lawley
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, TX, USA.,University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Lonnie G Petersen
- Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, Denmark
| | - Erin J Howden
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, TX, USA.,University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Satyam Sarma
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, TX, USA.,University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - William K Cornwell
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, TX, USA.,University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Rong Zhang
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, TX, USA.,University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Louis A Whitworth
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, TX, USA
| | - Michael A Williams
- Departments of Neurology and Neurological Surgery, University of Washington School of Medicine, Seattle, WA, USA
| | - Benjamin D Levine
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, TX, USA.,University of Texas Southwestern Medical Center, Dallas, TX, USA
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29
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Tian J, Liu J, Liu X, Xiao Y, Tang L. Intravitreal infusion: A novel approach for intraocular drug delivery. Sci Rep 2016; 6:37676. [PMID: 27886224 PMCID: PMC5122875 DOI: 10.1038/srep37676] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Accepted: 11/01/2016] [Indexed: 11/09/2022] Open
Abstract
Intraocular injection has become an increasingly important intervention in the treatment of posterior segment diseases. However, an acute intraocular pressure (IOP) elevation after intravitreal injection is a common concern. This study aimed to evaluate the efficacy of intravitreal infusion in maintaining stable IOP in a rabbit model. Trypan blue (TB) 0.06% with an external pump was used to evaluate intravitreal infusion in rabbit eyes. Groups A (50 μL), B (100 μL), C (150 μL), and D (200 μL) were slowly infused over 30 minutes with TB. As a control, Group E underwent conventional intravitreal injection of 100 μL of TB. Group F received a bolus infusion of 100 μL of TB within 1 minute. The mean increases in IOP during infusion for each group were: Group A (7.93 ± 3.80 mmHg), B (13.97 ± 3.17 mmHg), C (19.91 ± 6.06 mmHg) and D (29.38 ± 8.97 mmHg). Immediately post-injection in group E the mean increase in IOP amounted to 34.33 ± 6.57 mmHg. The mean increase in IOP of group F after bolus infusion was 49.89 ± 1.71 mmHg. Intravitreal infusion maintains a stable IOP and provides a controlled infusion speed compared with intravitreal injection.
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Affiliation(s)
- Jiao Tian
- Department of Ophthalmology and Centre of Eye Research, The Second Xiangya Hospital, Central South University, Changsha, China
| | - Jia Liu
- Department of Ophthalmology and Centre of Eye Research, The Second Xiangya Hospital, Central South University, Changsha, China
| | - Xiao Liu
- Department of Ophthalmology and Centre of Eye Research, The Second Xiangya Hospital, Central South University, Changsha, China
| | - Yangyan Xiao
- Department of Ophthalmology and Centre of Eye Research, The Second Xiangya Hospital, Central South University, Changsha, China
| | - Luosheng Tang
- Department of Ophthalmology and Centre of Eye Research, The Second Xiangya Hospital, Central South University, Changsha, China
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30
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Dibas A, Yorio T. Glucocorticoid therapy and ocular hypertension. Eur J Pharmacol 2016; 787:57-71. [PMID: 27388141 PMCID: PMC5014726 DOI: 10.1016/j.ejphar.2016.06.018] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Revised: 06/06/2016] [Accepted: 06/13/2016] [Indexed: 12/31/2022]
Abstract
The projected number of people who will develop age-related macular degeneration in estimated at 2020 is 196 million and is expected to reach 288 million in 2040. Also, the number of people with Diabetic retinopathy will grow from 126.6 million in 2010 to 191.0 million by 2030. In addition, it is estimated that there are 2.3 million people suffering from uveitis worldwide. Because of the anti-inflammatory properties of glucocorticoids (GCs), they are often used topically and/or intravitreally to treat ocular inflammation conditions or edema associated with macular degeneration and diabetic retinopathy. Unfortunately, ocular GC therapy can lead to severe side effects. Serious and sometimes irreversible eye damage can occur as a result of the development of GC-induced ocular hypertension causing secondary open-angle glaucoma. According to the world health organization, glaucoma is the second leading cause of blindness in the world and it is estimated that 80 million will suffer from glaucoma by 2020. In the current review, mechanisms of GC-induced damage in ocular tissue, GC-resistance, and enhancing GC therapy will be discussed.
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Affiliation(s)
- Adnan Dibas
- North Texas Eye Research Institute, UNT Health Science Center, Fort Worth, TX, USA.
| | - Thomas Yorio
- North Texas Eye Research Institute, UNT Health Science Center, Fort Worth, TX, USA
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31
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Choh V, Gurdita A, Tan B, Prasad RC, Bizheva K, Joos KM. Short-Term Moderately Elevated Intraocular Pressure Is Associated With Elevated Scotopic Electroretinogram Responses. Invest Ophthalmol Vis Sci 2016; 57:2140-51. [PMID: 27100161 PMCID: PMC4849866 DOI: 10.1167/iovs.15-18770] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Purpose Moderately elevated intraocular pressure (IOP) is a risk factor for open-angle glaucoma. Some patients suffer glaucoma despite clinically measured normal IOPs. Fluctuations in IOP may have a significant role since IOPs are higher during sleep and inversion activities. Controlled transient elevations of IOPs in rats over time lead to optic nerve structural changes that are similar to the early changes observed in constant chronic models of glaucoma. Because early intervention decreases glaucoma progression, this study was done to determine if early physiological changes to the retina could be detected with noninvasive electrophysiological and optical imaging tests during moderately elevated IOP. Methods Intraocular pressures were raised to moderately high levels (35 mm Hg) in one eye of Sprague-Dawley rats while the other (control) eye was untreated. One group of rats underwent scotopic threshold response (STR) and electroretinogram (ERG) testing, while another 3 groups underwent optical coherence tomography (OCT) imaging, Western blot, or histologic evaluation. Results The amplitudes of the STR and ERG responses in eyes with moderately elevated IOPs were enhanced compared to the values before IOP elevation, and compared to untreated contralateral eyes. Structural changes to the optic nerve also occurred during IOP elevation. Conclusions Although ischemic IOP elevations are well-known to globally reduce components of the scotopic ERG, acute elevation in rats to levels often observed in untreated glaucoma patients caused an increase in these parameters. Further exploration of these phenomena may be helpful in better understanding the mechanisms mediating early retinal changes during fluctuating or chronically elevated IOP.
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Affiliation(s)
- Vivian Choh
- School of Optometry and Vision Science University of Waterloo, Waterloo, Ontario, Canada
| | - Akshay Gurdita
- Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, Canada
| | - Bingyao Tan
- Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, Canada
| | - Ratna C Prasad
- Vanderbilt Eye Institute, Vanderbilt University, Nashville, Tennessee, United States
| | - Kostadinka Bizheva
- School of Optometry and Vision Science University of Waterloo, Waterloo, Ontario, Canada 2Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, Canada
| | - Karen M Joos
- Vanderbilt Eye Institute, Vanderbilt University, Nashville, Tennessee, United States
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