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Wang Q, Chen Y, Shen K, Zhou X, Shen M, Lu F, Zhu D. Spatial mapping of corneal biomechanical properties using wave-based optical coherence elastography. JOURNAL OF BIOPHOTONICS 2024; 17:e202300534. [PMID: 38453148 DOI: 10.1002/jbio.202300534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 01/20/2024] [Accepted: 02/11/2024] [Indexed: 03/09/2024]
Abstract
Quantifying the mechanical properties of the cornea can provide valuable insights into the occurrence and progression of keratoconus, as well as the effectiveness of corneal crosslinking surgery. This study presents a non-contact and non-invasive wave-based optical coherence elastography system that utilizes air-pulse stimulation to create a two-dimensional map of corneal elasticity. Homogeneous and dual concentration phantoms were measured with the sampling of 25 × 25 points over a 6.6 × 6.6 mm2 area, to verify the measurement capability for elastic mapping and the spatial resolution (0.91 mm). The velocity of elastic waves distribution of porcine corneas before and after corneal crosslinking surgery were further mapped, showing a significant change in biomechanics in crosslinked region. This system features non-invasiveness and high resolution, holding great potential for application in ophthalmic clinics.
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Affiliation(s)
- Qingying Wang
- Eye Hospital and School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Yulei Chen
- Department of Ophthalmology, Dongguan Tungwah Hospital, Dongguan, China
| | - Kexin Shen
- Eye Hospital and School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Xingyu Zhou
- Eye Hospital and School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Meixiao Shen
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, Wenzhou, China
| | - Fan Lu
- State Key Laboratory of Ophthalmology, Optometry and Visual Science, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
| | - Dexi Zhu
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, Wenzhou, China
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2
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Abstract
Purpose: Presbyopia-the progressive loss of near focus with age-is primarily a result of changes in lens biomechanics. In particular, the shape of the ocular lens in the absence of zonular tension changes significantly throughout adulthood. Contributors to this change in shape are changes in lens biomechanical properties, continuous volumetric growth lens, and possibly remodeling of the lens capsule. Knowledge in this area is growing rapidly, so the purpose of this mini-review was to summarize and synthesize these gains.Methods: We review the recent literature in this field.Results: The mechanisms governing age-related changes in biomechanical properties remains unknown. We have recently shown that lens growth may be driven by zonular tension. The same mechanobiological mechanism driving lens growth may also lead to remodeling of the capsule, though this remains to be demonstrated.Conclusions: This mini-review focuses on identifying mechanisms which cause these age-related changes, suggesting future work which may elucidate these mechanisms, and briefly discusses ongoing efforts to develop a non-surgical approach for therapeutic management of presbyopia. We also propose a simple model linking lens growth and biomechanical properties.
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Affiliation(s)
- Wade Rich
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Matthew A Reilly
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA.,Department of Ophthalmology & Visual Sciences, The Ohio State University, Columbus, OH, USA
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3
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Zhang H, Asroui L, Randleman JB, Scarcelli G. Motion-tracking Brillouin microscopy for in-vivo corneal biomechanics mapping. BIOMEDICAL OPTICS EXPRESS 2022; 13:6196-6210. [PMID: 36589595 PMCID: PMC9774862 DOI: 10.1364/boe.472053] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 10/08/2022] [Accepted: 10/09/2022] [Indexed: 05/28/2023]
Abstract
Corneal biomechanics play a critical role in maintaining corneal shape and thereby directly influence visual acuity. However, direct corneal biomechanical measurement in-vivo with sufficient accuracy and a high spatial resolution remains an open need. Here, we developed a three-dimensional (3D) motion-tracking Brillouin microscope for in-vivo corneal biomechanics mapping. The axial tracking utilized optical coherence tomography, which provided a tracking accuracy better than 3 µm. Meanwhile, 10 µm lateral tracking was achieved by tracking pupils with digital image processing. The 3D tracking enabled reconstruction of depth-dependent Brillouin distribution with a high spatial resolution. This superior technical performance enabled the capture of high-quality mechanical mapping in vivo even while the subject was breathing normally. Importantly, we improved Brillouin spectral measurements to achieve relative accuracy better than 0.07% verified by rubidium absorption frequencies, with 0.12% stability over 2000 seconds. These specifications finally yield the Brillouin measurement sensitivity that is required to detect ophthalmology-relevant corneal biomechanical properties.
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Affiliation(s)
- Hongyuan Zhang
- Cole Eye Institute, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44195, USA
| | - Lara Asroui
- Cole Eye Institute, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44195, USA
| | - J. Bradley Randleman
- Cole Eye Institute, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44195, USA
- Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, 9501 Euclid Ave, Cleveland, OH 44195, USA
| | - Giuliano Scarcelli
- Fischell Department of Bioengineering, University of Maryland, 8278 Paint Branch Drive, College Park, MD 20742, USA
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4
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Amini R, Bhatnagar A, Schlüßler R, Möllmert S, Guck J, Norden C. Amoeboid-like migration ensures correct horizontal cell layer formation in the developing vertebrate retina. eLife 2022; 11:e76408. [PMID: 35639083 PMCID: PMC9208757 DOI: 10.7554/elife.76408] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 05/30/2022] [Indexed: 11/16/2022] Open
Abstract
Migration of cells in the developing brain is integral for the establishment of neural circuits and function of the central nervous system. While migration modes during which neurons employ predetermined directional guidance of either preexisting neuronal processes or underlying cells have been well explored, less is known about how cells featuring multipolar morphology migrate in the dense environment of the developing brain. To address this, we here investigated multipolar migration of horizontal cells in the zebrafish retina. We found that these cells feature several hallmarks of amoeboid-like migration that enable them to tailor their movements to the spatial constraints of the crowded retina. These hallmarks include cell and nuclear shape changes, as well as persistent rearward polarization of stable F-actin. Interference with the organization of the developing retina by changing nuclear properties or overall tissue architecture hampers efficient horizontal cell migration and layer formation showing that cell-tissue interplay is crucial for this process. In view of the high proportion of multipolar migration phenomena observed in brain development, the here uncovered amoeboid-like migration mode might be conserved in other areas of the developing nervous system.
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Affiliation(s)
- Rana Amini
- Max Planck Institute of Molecular Cell Biology and GeneticsDresdenGermany
| | - Archit Bhatnagar
- Max Planck Institute of Molecular Cell Biology and GeneticsDresdenGermany
| | - Raimund Schlüßler
- Biotechnology Center, Center for Molecular and Cellular Bioengineering, Technische Universität DresdenDresdenGermany
| | - Stephanie Möllmert
- Biotechnology Center, Center for Molecular and Cellular Bioengineering, Technische Universität DresdenDresdenGermany
- Max Planck Institute for the Science of Light and Max-Planck-Zentrum für Physik und MedizinErlangenGermany
| | - Jochen Guck
- Biotechnology Center, Center for Molecular and Cellular Bioengineering, Technische Universität DresdenDresdenGermany
- Max Planck Institute for the Science of Light and Max-Planck-Zentrum für Physik und MedizinErlangenGermany
- Physics of Life, Technische Universität DresdenDresdenGermany
| | - Caren Norden
- Max Planck Institute of Molecular Cell Biology and GeneticsDresdenGermany
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6OeirasPortugal
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5
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Abstract
PURPOSE OF REVIEW Biomechanics is an important aspect of the complex family of diseases known as the glaucomas. Here, we review recent studies of biomechanics in glaucoma. RECENT FINDINGS Several tissues have direct and/or indirect biomechanical roles in various forms of glaucoma, including the trabecular meshwork, cornea, peripapillary sclera, optic nerve head/sheath, and iris. Multiple mechanosensory mechanisms and signaling pathways continue to be identified in both the trabecular meshwork and optic nerve head. Further, the recent literature describes a variety of approaches for investigating the role of tissue biomechanics as a risk factor for glaucoma, including pathological stiffening of the trabecular meshwork, peripapillary scleral structural changes, and remodeling of the optic nerve head. Finally, there have been advances in incorporating biomechanical information in glaucoma prognoses, including corneal biomechanical parameters and iridial mechanical properties in angle-closure glaucoma. SUMMARY Biomechanics remains an active aspect of glaucoma research, with activity in both basic science and clinical translation. However, the role of biomechanics in glaucoma remains incompletely understood. Therefore, further studies are indicated to identify novel therapeutic approaches that leverage biomechanics. Importantly, clinical translation of appropriate assays of tissue biomechanical properties in glaucoma is also needed.
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Affiliation(s)
- Babak N. Safa
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta GA, USA
| | - Cydney A. Wong
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta GA, USA
| | - Jungmin Ha
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta GA, USA
| | - C. Ross Ethier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta GA, USA
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Baumann B, Merkle CW, Augustin M, Glösmann M, Garhöfer G. Pulsatile tissue deformation dynamics of the murine retina and choroid mapped by 4D optical coherence tomography. BIOMEDICAL OPTICS EXPRESS 2022; 13:647-661. [PMID: 35284183 PMCID: PMC8884196 DOI: 10.1364/boe.445093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 12/20/2021] [Accepted: 12/28/2021] [Indexed: 05/11/2023]
Abstract
Irregular ocular pulsatility and altered mechanical tissue properties are associated with some of the most sight-threatening eye diseases. Here we present 4D optical coherence tomography (OCT) for the quantitative assessment and depth-resolved mapping of pulsatile dynamics in the murine retina and choroid. Through a pixel-wise analysis of phase changes of the complex OCT signal, we reveal spatiotemporal displacement characteristics across repeated frame acquisitions. We demonstrate in vivo fundus elastography (FUEL) imaging in wildtype mouse retinas and in a mouse model of retinal neovascularization and uncover subtle structural deformations related to ocular pulsation. Our data in mouse eyes hold promise for a powerful retinal elastography technique that may enable a new paradigm of OCT-based measurements and image contrast.
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Affiliation(s)
- Bernhard Baumann
- Center for Medical Physics and Biomedical
Engineering, Medical University of Vienna,
Währinger Gürtel 18-20, 1090 Vienna, Austria
| | - Conrad W. Merkle
- Center for Medical Physics and Biomedical
Engineering, Medical University of Vienna,
Währinger Gürtel 18-20, 1090 Vienna, Austria
| | - Marco Augustin
- Center for Medical Physics and Biomedical
Engineering, Medical University of Vienna,
Währinger Gürtel 18-20, 1090 Vienna, Austria
| | - Martin Glösmann
- Core Facility for Research and Technology,
University of Veterinary Medicine Vienna,
Veterinärplatz 1, 1210 Vienna, Austria
| | - Gerhard Garhöfer
- Department of Clinical Pharmacology,
Medical University of Vienna, Währinger
Gürtel 18-20, 1090 Vienna, Austria
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7
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Sun MG, Son T, Crutison J, Guaiquil V, Lin S, Nammari L, Klatt D, Yao X, Rosenblatt MI, Royston TJ. Optical coherence elastography for assessing the influence of intraocular pressure on elastic wave dispersion in the cornea. J Mech Behav Biomed Mater 2022; 128:105100. [PMID: 35121423 PMCID: PMC8904295 DOI: 10.1016/j.jmbbm.2022.105100] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 01/17/2022] [Accepted: 01/21/2022] [Indexed: 10/19/2022]
Abstract
The cornea is a highly specialized organ that relies on its mechanical stiffness to maintain its aspheric geometry and refractive power, and corneal diseases such as keratoconus have been linked to abnormal tissue stiffness and biomechanics. Dynamic optical coherence elastography (OCE) is a clinically promising non-contact and non-destructive imaging technique that can provide measurements of corneal tissue stiffness directly in vivo. The method relies on the concepts of elastography where shear waves are generated and imaged within a tissue to obtain mechanical properties such as tissue stiffness. The accuracy of OCE-based measurements is ultimately dependent on the mathematical theories used to model wave behavior in the tissue of interest. In the cornea, elastic waves propagate as guided wave modes which are highly dispersive and can be mathematically complex to model. While recent groups have developed detailed theories for estimating corneal tissue properties from guided wave behavior, the effects of intraocular pressure (IOP)-induced prestress have not yet been considered. It is known that prestress alone can strongly influence wave behavior, in addition to the associated non-linear changes in tissue properties. This present study shows that failure to account for the effects of prestress may result in overestimations of the corneal shear moduli, particularly at high IOPs. We first examined the potential effects of IOP and IOP-induced prestress using a combination of approximate mathematical theories describing wave behavior in thin plates with observations made from data published in the OCE literature. Through wave dispersion analysis, we deduce that IOP introduces a tensile hoop stress and may also influence an elastic foundational effect that were observable in the low-frequency components of the dispersion curves. These effects were incorporated into recently developed models of wave behavior in nearly incompressible, transversely isotropic (NITI) materials. Fitting of the modified NITI model with ex vivo porcine corneal data demonstrated that incorporation of the effects of IOP resulted in reduced estimates of corneal shear moduli. We believe this demonstrates that overestimation of corneal stiffness occurs if IOP is not taken into consideration. Our work may be helpful in separating inherent corneal stiffness properties that are independent of IOP; changes in these properties and in IOP are distinct, clinically relevant issues that affect the cornea health.
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8
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Karamichos D, Escandon P, Vasini B, Nicholas SE, Van L, Dang DH, Cunningham RL, Riaz KM. Anterior pituitary, sex hormones, and keratoconus: Beyond traditional targets. Prog Retin Eye Res 2021; 88:101016. [PMID: 34740824 PMCID: PMC9058044 DOI: 10.1016/j.preteyeres.2021.101016] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Revised: 10/15/2021] [Accepted: 10/18/2021] [Indexed: 12/13/2022]
Abstract
"The Diseases of the Horny-coat of The Eye", known today as keratoconus, is a progressive, multifactorial, non-inflammatory ectatic corneal disorder that is characterized by steepening (bulging) and thinning of the cornea, irregular astigmatism, myopia, and scarring that can cause devastating vision loss. The significant socioeconomic impact of the disease is immeasurable, as patients with keratoconus can have difficulties securing certain jobs or even joining the military. Despite the introduction of corneal crosslinking and improvements in scleral contact lens designs, corneal transplants remain the main surgical intervention for treating keratoconus refractory to medical therapy and visual rehabilitation. To-date, the etiology and pathogenesis of keratoconus remains unclear. Research studies have increased exponentially over the years, highlighting the clinical significance and international interest in this disease. Hormonal imbalances have been linked to keratoconus, both clinically and experimentally, with both sexes affected. However, it is unclear how (molecular/cellular signaling) or when (age/disease stage(s)) those hormones affect the keratoconic cornea. Previous studies have categorized the human cornea as an extragonadal tissue, showing modulation of the gonadotropins, specifically luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Studies herein provide new data (both in vitro and in vivo) to further delineate the role of hormones/gonadotropins in the keratoconus pathobiology, and propose the existence of a new axis named the Hypothalamic-Pituitary-Adrenal-Corneal (HPAC) axis.
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Affiliation(s)
- Dimitrios Karamichos
- North Texas Eye Research Institute, University of North Texas Health Science Center, 3430 Camp Bowie Blvd, Fort Worth, TX, 76107, USA; Department of Pharmaceutical Sciences, University of North Texas Health Science Center, 3500 Camp Bowie Blvd, Fort Worth, TX, 76107, USA; Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, 3500 Camp Bowie Blvd, Fort Worth, TX, 76107, USA.
| | - Paulina Escandon
- North Texas Eye Research Institute, University of North Texas Health Science Center, 3430 Camp Bowie Blvd, Fort Worth, TX, 76107, USA; Department of Pharmaceutical Sciences, University of North Texas Health Science Center, 3500 Camp Bowie Blvd, Fort Worth, TX, 76107, USA
| | - Brenda Vasini
- North Texas Eye Research Institute, University of North Texas Health Science Center, 3430 Camp Bowie Blvd, Fort Worth, TX, 76107, USA; Department of Pharmaceutical Sciences, University of North Texas Health Science Center, 3500 Camp Bowie Blvd, Fort Worth, TX, 76107, USA
| | - Sarah E Nicholas
- North Texas Eye Research Institute, University of North Texas Health Science Center, 3430 Camp Bowie Blvd, Fort Worth, TX, 76107, USA; Department of Pharmaceutical Sciences, University of North Texas Health Science Center, 3500 Camp Bowie Blvd, Fort Worth, TX, 76107, USA
| | - Lyly Van
- University of Oklahoma Health Sciences Center, 940 Stanton L Young, Oklahoma City, OK, USA; Department of Ophthalmology, Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Deanna H Dang
- College of Medicine, University of Oklahoma Health Sciences Center, 940 Stanton L Young, Oklahoma City, OK, USA
| | - Rebecca L Cunningham
- Department of Pharmaceutical Sciences, University of North Texas Health Science Center, 3500 Camp Bowie Blvd, Fort Worth, TX, 76107, USA
| | - Kamran M Riaz
- Department of Ophthalmology, Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
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9
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Zhu Z, Waxman S, Wang B, Wallace J, Schmitt SE, Tyler-Kabara E, Ishikawa H, Schuman JS, Smith MA, Wollstein G, Sigal IA. Interplay between intraocular and intracranial pressure effects on the optic nerve head in vivo. Exp Eye Res 2021; 213:108809. [PMID: 34736887 DOI: 10.1016/j.exer.2021.108809] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 10/19/2021] [Accepted: 10/25/2021] [Indexed: 12/19/2022]
Abstract
Intracranial pressure (ICP) has been proposed to play an important role in the sensitivity to intraocular pressure (IOP) and susceptibility to glaucoma. However, the in vivo effects of simultaneous, controlled, acute variations in ICP and IOP have not been directly measured. We quantified the deformations of the anterior lamina cribrosa (ALC) and scleral canal at Bruch's membrane opening (BMO) under acute elevation of IOP and/or ICP. Four eyes of three adult monkeys were imaged in vivo with OCT under four pressure conditions: IOP and ICP either at baseline or elevated. The BMO and ALC were reconstructed from manual delineations. From these, we determined canal area at the BMO (BMO area), BMO aspect ratio and planarity, and ALC median depth relative to the BMO plane. To better account for the pressure effects on the imaging, we also measured ALC visibility as a percent of the BMO area. Further, ALC depths were analyzed only in regions where the ALC was visible in all pressure conditions. Bootstrap sampling was used to obtain mean estimates and confidence intervals, which were then used to test for significant effects of IOP and ICP, independently and in interaction. Response to pressure manipulation was highly individualized between eyes, with significant changes detected in a majority of the parameters. Significant interactions between ICP and IOP occurred in all measures, except ALC visibility. On average, ICP elevation expanded BMO area by 0.17 mm2 at baseline IOP, and contracted BMO area by 0.02 mm2 at high IOP. ICP elevation decreased ALC depth by 10 μm at baseline IOP, but increased depth by 7 μm at high IOP. ALC visibility decreased as ICP increased, both at baseline (-10%) and high IOP (-17%). IOP elevation expanded BMO area by 0.04 mm2 at baseline ICP, and contracted BMO area by 0.09 mm2 at high ICP. On average, IOP elevation caused the ALC to displace 3.3 μm anteriorly at baseline ICP, and 22 μm posteriorly at high ICP. ALC visibility improved as IOP increased, both at baseline (5%) and high ICP (8%). In summary, changing IOP or ICP significantly deformed both the scleral canal and the lamina of the monkey ONH, regardless of the other pressure level. There were significant interactions between the effects of IOP and those of ICP on LC depth, BMO area, aspect ratio and planarity. On most eyes, elevating both pressures by the same amount did not cancel out the effects. Altogether our results show that ICP affects sensitivity to IOP, and thus that it can potentially also affect susceptibility to glaucoma.
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Affiliation(s)
- Ziyi Zhu
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
| | - Susannah Waxman
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Bo Wang
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA; Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Jacob Wallace
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Samantha E Schmitt
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA; Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Elizabeth Tyler-Kabara
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, PA, USA; Department of Neurosurgery, University of Texas-Austin, Austin, TX, USA
| | - Hiroshi Ishikawa
- Department of Ophthalmology, NYU School of Medicine, New York, NY, USA
| | - Joel S Schuman
- Department of Ophthalmology, NYU School of Medicine, New York, NY, USA
| | - Matthew A Smith
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA; Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Gadi Wollstein
- Department of Ophthalmology, NYU School of Medicine, New York, NY, USA
| | - Ian A Sigal
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA.
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10
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Bontzos G, Douglas VP, Douglas KAA, Kapsala Z, Drakonaki EE, Detorakis ET. Ultrasound Elastography in Ocular and Periocular Tissues: A Review. Curr Med Imaging 2021; 17:1041-1053. [PMID: 33319691 DOI: 10.2174/1573405616666201214123117] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Revised: 08/31/2020] [Accepted: 10/15/2020] [Indexed: 11/22/2022]
Abstract
Ultrasound elastography has become available in everyday practice, allowing direct measurement of tissue elasticity with important and expanding clinical applications. Several studies that have evaluated pathological and non-pathological tissues have demonstrated that ultrasound elastography can actually improve the diagnostic accuracy of the underlying disease process by detecting differences in their elasticity. Ocular and periocular tissues can also be characterized by their elastic properties. In this context, a comprehensive review of literature on ultrasound elastography as well as its current applications in Ophthalmology is presented.
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Affiliation(s)
- Georgios Bontzos
- Department of Ophthalmology, University Hospital of Heraklion, Crete, Greece
| | | | | | - Zoi Kapsala
- Department of Ophthalmology, University Hospital of Heraklion, Crete, Greece
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11
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Rojananuangnit K. Corneal Hysteresis in Thais and Variation of Corneal Hysteresis in Glaucoma. CLINICAL OPTOMETRY 2021; 13:287-299. [PMID: 34629920 PMCID: PMC8493478 DOI: 10.2147/opto.s324187] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 09/16/2021] [Indexed: 06/13/2023]
Abstract
PURPOSE To collect the normal value data of corneal hysteresis in Thais and study the variation of corneal hysteresis in glaucomatous eyes. METHODS Retrospective cross-sectional study of corneal hysteresis (CH) in healthy non-glaucomatous and glaucomatous eyes. Demographic data, type and staging of glaucoma, Goldmann applanation tonometry (GAT) and ocular response analyzer parameters; CH, corneal-compensated intraocular pressure (IOPcc) and Goldmann-correlated intraocular pressure (IOPg) were collected. RESULTS Data from one eye of 465 normal participants were included for the normal value data of CH. Mean CH, IOPcc and IOPg were 10.18 ± 1.48, 15.01 ± 3.04 and 14.16 ± 3.06 mmHg, respectively. Average age was 57.21 ± 14.4 years. CH at the fifth percentile was 8.0 mmHg. Women had significantly higher CH than men (10.29 ± 1.46 vs 9.90 ± 1.49 mmHg, p=0.009). Moderate negative correlation was found between age and CH, r = -0.338, p<0.001. There were 695 glaucomatous eyes from 429 patients including primary-open angle glaucoma (POAG), primary close-angle glaucoma (PACG), normal tension glaucoma (NTG) and ocular hypertension (OHT). CH in each glaucoma type and severity stage (early, moderate and severe) were as follows: POAG: 8.74 ± 1.52 mmHg (9.22 ± 1.47, 8.74 ± 1.23 and 7.92 ± 1.40 mmHg, p<0.001), PACG: 9.09 ± 1.72 mmHg (9.85 ± 1.45, 9.04 ± 1.68 and 8.45 ± 1.74 mmHg, p= 0.004), NTG: 9.55 ± 1.67 mmHg (9.47 ± 1.38, 9.75 ± 2.42 and 9.77 ± 1.34 mmHg, p 0.525) and OHT: 10.10 ± 1.40 mmHg. CONCLUSION Compared with normal value data of corneal hysteresis, CH in glaucomatous eyes was lower. The more advanced glaucoma stage was associated with lower CH. Arising from normal value data, a low percentile of CH could be applied as the deviation value from normal and this dynamic property of CH could represent a glaucoma predictor in an effort to improve glaucoma care.
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Affiliation(s)
- Kulawan Rojananuangnit
- Glaucoma Unit, Ophthalmology Department, Mettapracharak (Wat Rai Khing) Hospital, Nakhon Pathom, Thailand
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12
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Kim J, Gardiner SK, Ramazzotti A, Karuppanan U, Bruno L, Girkin CA, Downs JC, Fazio MA. Strain by virtual extensometers and video-imaging optical coherence tomography as a repeatable metric for IOP-Induced optic nerve head deformations. Exp Eye Res 2021; 211:108724. [PMID: 34375590 PMCID: PMC8511063 DOI: 10.1016/j.exer.2021.108724] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 07/27/2021] [Accepted: 08/06/2021] [Indexed: 11/20/2022]
Abstract
PURPOSE To determine if in vivo strain response of the Optic Nerve Head (ONH) to IOP elevation visualized using Optical Coherence Tomography (OCT) video imaging and quantified using novel virtual extensometers was able to be provided repeatable measurements of tissue specific deformations. METHODS The ONHs of 5 eyes from 5 non-human primates (NHPs) were imaged by Spectralis OCT. A vertical and a horizontal B-scan of the ONH were continuously recorded for 60 s at 6 Hz (video imaging mode) during IOP elevation from 10 to 30 mmHg. Imaging was repeated over three imaging sessions. The 2D normal strain was computed by template-matching digital image correlation using virtual extensometers. ANOVA F-test (F) was used to compare inter-eye, inter-session, and inter-tissue variability for the prelaminar, Bruch's membrane opening (BMO), lamina cribrosa (LC) and choroidal regions (against variance the error term). F-test of the ratio between inter-eye to inter-session variability was used to test for strain repeatability across imaging sessions (FIS). RESULTS Variability of strain across imaging session (F = 0.7263, p = 0.4855) and scan orientation was not significant (F = 1.053, p = 0.3066). Inter session variability of strain was significantly lower than inter-eye variability (FIS = 22.63, p = 0.0428) and inter-tissue variability (FIS = 99.33 p = 0.00998). After IOP elevation, strain was highest in the choroid (-18.11%, p < 0.001), followed by prelaminar tissue (-11.0%, p < 0.001), LC (-3.79%, p < 0.001), and relative change in BMO diameter (-0.57%, p = 0.704). CONCLUSIONS Virtual extensometers applied to video-OCT were sensitive to the eye-specific and tissue-specific mechanical response of the ONH to IOP and were repeatable across imaging sessions.
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Affiliation(s)
- Jihee Kim
- Biomedical Engineering, University of Alabama at Birmingham, Birmingham, AL, USA
| | | | - Andrea Ramazzotti
- Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Udayakumar Karuppanan
- Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Luigi Bruno
- Department of Mechanical, Energy and Management Engineering, University of Calabria, Rende, CS, Italy
| | - Christopher A Girkin
- Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, USA
| | - J Crawford Downs
- Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Massimo A Fazio
- Biomedical Engineering, University of Alabama at Birmingham, Birmingham, AL, USA; Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, USA; The Viterbi Family Department of Ophthalmology, UC San Diego, La Jolla, CA, USA.
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13
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Kirby MA, Pitre JJ, Liou HC, Li DS, Wang RK, Pelivanov I, O’Donnell M, Shen TT. Delineating Corneal Elastic Anisotropy in a Porcine Model Using Noncontact OCT Elastography and Ex Vivo Mechanical Tests. OPHTHALMOLOGY SCIENCE 2021; 1:100058. [PMID: 36246948 PMCID: PMC9560544 DOI: 10.1016/j.xops.2021.100058] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Revised: 09/14/2021] [Accepted: 09/15/2021] [Indexed: 11/30/2022]
Abstract
Purpose To compare noncontact acoustic microtapping (AμT) OCT elastography (OCE) with destructive mechanical tests to confirm corneal elastic anisotropy. Design Ex vivo laboratory study with noncontact AμT-OCE followed by mechanical rheometry and extensometry. Participants Inflated cornea of whole-globe porcine eyes (n = 9). Methods A noncontact AμT transducer was used to launch propagating mechanical waves in the cornea that were imaged with phase-sensitive OCT at physiologically relevant controlled pressures. Reconstruction of both Young's modulus (E) and out-of-plane shear modulus (G) in the cornea from experimental data was performed using a nearly incompressible transversely isotropic (NITI) medium material model assuming spatial isotropy of corneal tensile properties. Corneal samples were excised and parallel plate rheometry was performed to measure shear modulus, G. Corneal samples were then subjected to strip extensometry to measure the Young's modulus, E. Main Outcome Measures Strong corneal anisotropy was confirmed with both AμT-OCE and mechanical tests, with the Young's (E) and shear (G) moduli differing by more than an order of magnitude. These results show that AμT-OCE can quantify both moduli simultaneously with a noncontact, noninvasive, clinically translatable technique. Results Mean of the OCE measured moduli were E = 12 ± 5 MPa and G = 31 ± 11 kPa at 5 mmHg and E = 20 ± 9 MPa and G = 61 ± 29 kPa at 20 mmHg. Tensile testing yielded a mean Young's modulus of 1 MPa - 20 MPa over a strain range of 1% to 7%. Shear storage and loss modulus (G'/G'') measured with rheometry was approximately 82/13 ± 12/4 kPa at 0.2 Hz and 133/29 ± 16/3 kPa at 16 Hz (0.1% strain). Conclusions The cornea is confirmed to be a strongly anisotropic elastic material that cannot be characterized with a single elastic modulus. The NITI model is the simplest one that accounts for the cornea's incompressibility and in-plane distribution of lamellae. AμT-OCE has been shown to be the only reported noncontact, noninvasive method to measure both elastic moduli. Submillimeter spatial resolution and near real-time operation can be achieved. Quantifying corneal elasticity in vivo will enable significant innovation in ophthalmology, helping to develop personalized biomechanical models of the eye that can predict response to ophthalmic interventions.
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Affiliation(s)
- Mitchell A. Kirby
- Department of Bioengineering, University of Washington, Seattle, Washington
| | - John J. Pitre
- Department of Bioengineering, University of Washington, Seattle, Washington
| | - Hong-Cin Liou
- Department of Bioengineering, University of Washington, Seattle, Washington
| | - David S. Li
- Department of Bioengineering, University of Washington, Seattle, Washington
| | - Ruikang K. Wang
- Department of Bioengineering, University of Washington, Seattle, Washington,Department of Ophthalmology, University of Washington, Seattle, Washington
| | - Ivan Pelivanov
- Department of Bioengineering, University of Washington, Seattle, Washington
| | - Matthew O’Donnell
- Department of Bioengineering, University of Washington, Seattle, Washington
| | - Tueng T. Shen
- Department of Bioengineering, University of Washington, Seattle, Washington,Department of Ophthalmology, University of Washington, Seattle, Washington,Correspondence: Tueng T. Shen, MD, PhD, Department of Bioengineering, University of Washington, 3720 15th Ave NE, Seattle, WA 98105.
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14
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Rioboó RJJ, Gontán N, Sanderson D, Desco M, Gómez-Gaviro MV. Brillouin Spectroscopy: From Biomedical Research to New Generation Pathology Diagnosis. Int J Mol Sci 2021; 22:8055. [PMID: 34360822 PMCID: PMC8347166 DOI: 10.3390/ijms22158055] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Revised: 07/11/2021] [Accepted: 07/23/2021] [Indexed: 01/06/2023] Open
Abstract
Brillouin spectroscopy has recently gained considerable interest within the biomedical field as an innovative tool to study mechanical properties in biology. The Brillouin effect is based on the inelastic scattering of photons caused by their interaction with thermodynamically driven acoustic modes or phonons and it is highly dependent on the material's elasticity. Therefore, Brillouin is a contactless, label-free optic approach to elastic and viscoelastic analysis that has enabled unprecedented analysis of ex vivo and in vivo mechanical behavior of several tissues with a micrometric resolution, paving the way to a promising future in clinical diagnosis. Here, we comprehensively review the different studies of this fast-moving field that have been performed up to date to provide a quick guide of the current literature. In addition, we offer a general view of Brillouin's biomedical potential to encourage its further development to reach its implementation as a feasible, cost-effective pathology diagnostic tool.
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Affiliation(s)
- Rafael J. Jiménez Rioboó
- Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC), C/Sor Juana Inés de la Cruz, 3, 28049 Madrid, Spain;
| | - Nuria Gontán
- Instituto de Investigación Sanitaria Gregorio Marañón, 28007 Madrid, Spain; (N.G.); (D.S.)
- Departamento de Bioingeniería e Ingeniería Aeroespacial, Universidad Carlos III, 28911 Madrid, Spain
| | - Daniel Sanderson
- Instituto de Investigación Sanitaria Gregorio Marañón, 28007 Madrid, Spain; (N.G.); (D.S.)
- Departamento de Bioingeniería e Ingeniería Aeroespacial, Universidad Carlos III, 28911 Madrid, Spain
| | - Manuel Desco
- Instituto de Investigación Sanitaria Gregorio Marañón, 28007 Madrid, Spain; (N.G.); (D.S.)
- Departamento de Bioingeniería e Ingeniería Aeroespacial, Universidad Carlos III, 28911 Madrid, Spain
- Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), 28029 Madrid, Spain
- Centro Nacional de Investigaciones Cardiovasculares Carlos III, 28029 Madrid, Spain
| | - Maria Victoria Gómez-Gaviro
- Instituto de Investigación Sanitaria Gregorio Marañón, 28007 Madrid, Spain; (N.G.); (D.S.)
- Departamento de Bioingeniería e Ingeniería Aeroespacial, Universidad Carlos III, 28911 Madrid, Spain
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15
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Puyo L, David C, Saad R, Saad S, Gautier J, Sahel JA, Borderie V, Paques M, Atlan M. Laser Doppler holography of the anterior segment for blood flow imaging, eye tracking, and transparency assessment. BIOMEDICAL OPTICS EXPRESS 2021; 12:4478-4495. [PMID: 34457427 PMCID: PMC8367265 DOI: 10.1364/boe.425272] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 05/28/2021] [Accepted: 05/30/2021] [Indexed: 05/04/2023]
Abstract
Laser Doppler holography (LDH) is a full-field blood flow imaging technique able to reveal human retinal and choroidal blood flow with high temporal resolution. We here report on using LDH in the anterior segment of the eye without making changes to the instrument. Blood flow in the bulbar conjunctiva and episclera as well as in corneal neovascularization can be effectively imaged. We additionally demonstrate simultaneous holographic imaging of the anterior and posterior segments by simply adapting the numerical propagation distance to the plane of interest. We used this feature to track the movements of the retina and pupil with high temporal resolution. Finally, we show that the light backscattered by the retina can be used for retro-illumination of the anterior segment. Hence digital holography can reveal opacities caused by absorption or diffusion in the cornea and eye lens.
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Affiliation(s)
- Léo Puyo
- Centre Hospitalier National d’Ophtalmologie des Quinze-Vingts, INSERM-DHOS CIC 1423, 28 rue de Charenton, 75012 Paris, France
- Paris Eye Imaging, France
- Institute of Biomedical Optics, University of Lübeck. Peter-Monnik-Weg 4, 23562 Lübeck, Germany
| | - Clémentine David
- Centre Hospitalier National d’Ophtalmologie des Quinze-Vingts, INSERM-DHOS CIC 1423, 28 rue de Charenton, 75012 Paris, France
| | - Rana Saad
- Centre Hospitalier National d’Ophtalmologie des Quinze-Vingts, INSERM-DHOS CIC 1423, 28 rue de Charenton, 75012 Paris, France
- Paris Eye Imaging, France
| | - Sami Saad
- Centre Hospitalier National d’Ophtalmologie des Quinze-Vingts, INSERM-DHOS CIC 1423, 28 rue de Charenton, 75012 Paris, France
| | - Josselin Gautier
- Centre Hospitalier National d’Ophtalmologie des Quinze-Vingts, INSERM-DHOS CIC 1423, 28 rue de Charenton, 75012 Paris, France
- Paris Eye Imaging, France
| | - José Alain Sahel
- Centre Hospitalier National d’Ophtalmologie des Quinze-Vingts, INSERM-DHOS CIC 1423, 28 rue de Charenton, 75012 Paris, France
- Paris Eye Imaging, France
- Department of Ophthalmology, The University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
- Institut de la Vision, Sorbonne Université, INSERM, CNRS, 17 Rue Moreau, 75012 Paris, France
| | - Vincent Borderie
- Centre Hospitalier National d’Ophtalmologie des Quinze-Vingts, INSERM-DHOS CIC 1423, 28 rue de Charenton, 75012 Paris, France
| | - Michel Paques
- Centre Hospitalier National d’Ophtalmologie des Quinze-Vingts, INSERM-DHOS CIC 1423, 28 rue de Charenton, 75012 Paris, France
- Paris Eye Imaging, France
- Institut de la Vision, Sorbonne Université, INSERM, CNRS, 17 Rue Moreau, 75012 Paris, France
| | - Michael Atlan
- Paris Eye Imaging, France
- Institut Langevin, CNRS, PSL University, ESPCI Paris, 1 rue Jussieu, 75005 Paris, France
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16
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Song Y, Fang L, Zhu Q, Du R, Guo B, Gong J, Huang J. Biomechanical responses of the cornea after small incision lenticule extraction (SMILE) refractive surgery based on a finite element model of the human eye. MATHEMATICAL BIOSCIENCES AND ENGINEERING : MBE 2021; 18:4212-4225. [PMID: 34198433 DOI: 10.3934/mbe.2021211] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
PURPOSE To investigate the biomechanical responses of the human cornea after small incision lenticule extraction (SMILE) procedures, especially their effects of SMILE surgery on stress and strain. METHODS Based on finite element analysis, a three-dimensional (3D) model of the human eye was established to simulate SMILE refractive surgery procedures. Stress and strain values were calculated by inputting the intraocular pressure (IOP). RESULTS After SMILE refractive surgery procedures, the stress and strain of the anterior and posterior corneal surfaces were significantly increased. The equivalent stress and strain on the anterior and posterior corneal surfaces increased with increasing diopter and were concentrated in the central area, whereas the values of stress and strain at the incision site on the anterior surface of the cornea were approximately 0. Compared with the anterior corneal surface, the stress and strain of the posterior surface were larger. Increasing IOP caused an approximately linear change in stress and a nonlinear increase in corneal strain. In addition, we found that the incision sizes and direction had less of an influence on stress and strain. In summary, SMILE surgery increased the equivalent stress and strain on the human cornea. CONCLUSIONS The equivalent stress and strain of the anterior and posterior human corneal surfaces increased after SMILE refractive surgery; these increases were particularly noticeable on the posterior surface of the cornea.
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Affiliation(s)
- Yinyu Song
- Key Laboratory of Nondestructive Test (Ministry of Education), Nanchang Hangkong University, Nanchang 330063, China
| | - Lihua Fang
- Key Laboratory of Nondestructive Test (Ministry of Education), Nanchang Hangkong University, Nanchang 330063, China
| | - Qinyue Zhu
- Key Laboratory of Nondestructive Test (Ministry of Education), Nanchang Hangkong University, Nanchang 330063, China
| | - Ruirui Du
- Key Laboratory of Nondestructive Test (Ministry of Education), Nanchang Hangkong University, Nanchang 330063, China
| | - Binhui Guo
- Key Laboratory of Nondestructive Test (Ministry of Education), Nanchang Hangkong University, Nanchang 330063, China
| | - Jiahui Gong
- Key Laboratory of Nondestructive Test (Ministry of Education), Nanchang Hangkong University, Nanchang 330063, China
| | - Jixia Huang
- Key Laboratory of Nondestructive Test (Ministry of Education), Nanchang Hangkong University, Nanchang 330063, China
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17
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Brazile BL, Yang B, Waxman S, Lam P, Voorhees AP, Hua Y, Loewen RT, Loewen NA, Rizzo JF, Jakobs T, Sigal IA. Lamina Cribrosa Capillaries Straighten as Intraocular Pressure Increases. Invest Ophthalmol Vis Sci 2021; 61:2. [PMID: 33001158 PMCID: PMC7545063 DOI: 10.1167/iovs.61.12.2] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Purpose The purpose of this study was to visualize the lamina cribrosa (LC) capillaries and collagenous beams, measure capillary tortuosity (path length over straight end-to-end length), and determine if capillary tortuosity changes when intraocular pressure (IOP) increases. Methods Within 8 hours of sacrifice, 3 pig heads were cannulated via the external ophthalmic artery, perfused with PBS to remove blood, and then perfused with a fluorescent dye to label the capillaries. The posterior pole of each eye was mounted in a custom-made inflation chamber for control of IOP with simultaneous imaging. Capillaries and collagen beams were visualized with structured light illumination enhanced imaging at IOPs from 5 to 50 mm Hg at each 5 mm Hg increment. Capillary tortuosity was measured from the images and paired two-sample t-tests were used to assess for significant changes in relation to changes in IOP. Results Capillaries were highly tortuous at 15 mm Hg (up to 1.45). In all but one eye, tortuosity decreased significantly as IOP increased from 15 to 25 mm Hg (P < 0.01), and tortuosity decreased significantly in every eye as IOP increased from 15 to 40 mm Hg (P < 0.01). In only 16% of capillaries, tortuosity increased with elevated IOP. Capillaries had a surprisingly different topology from the collagen beams. Conclusions Although high capillary tortuosity is sometimes regarded as potentially problematic because it can reduce blood flow, LC capillary tortuosity may provide slack that mitigates against reduced flow and structural damage caused by excessive stretch under elevated IOP. We speculate that low capillary tortuosity could be a risk factor for damage under high IOP.
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Affiliation(s)
- Bryn L Brazile
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh Pennsylvania, United States
| | - Bin Yang
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh Pennsylvania, United States.,Department of Engineering, Duquesne University, Pittsburgh Pennsylvania, United States
| | - Susannah Waxman
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh Pennsylvania, United States
| | - Po Lam
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh Pennsylvania, United States
| | - Andrew P Voorhees
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh Pennsylvania, United States
| | - Yi Hua
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh Pennsylvania, United States
| | - Ralitsa T Loewen
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh Pennsylvania, United States
| | - Nils A Loewen
- Department of Ophthalmology, University of Würzburg, Würzburg, Germany
| | - Joseph F Rizzo
- Neuro-Ophthalmology Service, Department of Ophthalmology, Massachusetts Eye and Ear and Harvard Medical School, Boston, Massachusetts, United States
| | - Tatjana Jakobs
- Department of Ophthalmology, Harvard Medical School, Boston Massachusetts, United States
| | - Ian A Sigal
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh Pennsylvania, United States.,Department of Bioengineering, University of Pittsburgh, Pittsburgh Pennsylvania, United States
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18
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Ferrara M, Lugano G, Sandinha MT, Kearns VR, Geraghty B, Steel DHW. Biomechanical properties of retina and choroid: a comprehensive review of techniques and translational relevance. Eye (Lond) 2021; 35:1818-1832. [PMID: 33649576 PMCID: PMC8225810 DOI: 10.1038/s41433-021-01437-w] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 12/06/2020] [Accepted: 01/26/2021] [Indexed: 02/06/2023] Open
Abstract
Studying the biomechanical properties of biological tissue is crucial to improve our understanding of disease pathogenesis. The biomechanical characteristics of the cornea, sclera and the optic nerve head have been well addressed with an extensive literature and an in-depth understanding of their significance whilst, in comparison, knowledge of the retina and choroid is relatively limited. Knowledge of these tissues is important not only to clarify the underlying pathogenesis of a wide variety of retinal and vitreoretinal diseases, including age-related macular degeneration, hereditary retinal dystrophies and vitreoretinal interface diseases but also to optimise the surgical handling of retinal tissues and, potentially, the design and properties of implantable retinal prostheses and subretinal therapies. Our aim with this article is to comprehensively review existing knowledge of the biomechanical properties of retina, internal limiting membrane (ILM) and the Bruch’s membrane–choroidal complex (BMCC), highlighting the potential implications for clinical and surgical practice. Prior to this we review the testing methodologies that have been used both in vitro, and those starting to be used in vivo to aid understanding of their results and significance.
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Affiliation(s)
| | - Gaia Lugano
- Department of Eye and Vision Science, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK
| | | | - Victoria R Kearns
- Department of Eye and Vision Science, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK
| | - Brendan Geraghty
- Musculoskeletal and Ageing Science, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK.
| | - David H W Steel
- Sunderland Eye Infirmary, Sunderland, UK. .,Bioscience Institute, Newcastle University, Newcastle Upon Tyne, UK.
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19
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Zhu Y, Zhang Y, Shi G, Xue Q, Han X, Ai S, Shi J, Xie C, He X. Quantification of iris elasticity using acoustic radiation force optical coherence elastography. APPLIED OPTICS 2020; 59:10739-10745. [PMID: 33361893 DOI: 10.1364/ao.406190] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Accepted: 10/19/2020] [Indexed: 06/12/2023]
Abstract
Careful quantification of the changes in biomechanical properties of the iris can offer insight into the pathophysiology of some ocular diseases. However, to date there has not been much information available regarding this subject because clinical detection for iris elasticity remains challenging. To overcome this limitation, we explore, for the first time to our knowledge, the potential of measuring iris elasticity using acoustic radiation force optical coherence elastography (ARF-OCE). The resulting images and shear wave propagation, as well as the corresponding shear modulus and Young's modulus from ex vivo and in vivo rabbit models confirmed the feasibility of this method. With features of noninvasive imaging, micrometer-scale resolution, high acquisition speed and real-time processing, ARF-OCE is a promising method for reconstruction of iris elasticity and may have great potential to be applied in clinical ophthalmology with further refinement.
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20
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Curatolo A, Birkenfeld JS, Martinez-Enriquez E, Germann JA, Muralidharan G, Palací J, Pascual D, Eliasy A, Abass A, Solarski J, Karnowski K, Wojtkowski M, Elsheikh A, Marcos S. Multi-meridian corneal imaging of air-puff induced deformation for improved detection of biomechanical abnormalities. BIOMEDICAL OPTICS EXPRESS 2020; 11:6337-6355. [PMID: 33282494 PMCID: PMC7687933 DOI: 10.1364/boe.402402] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 09/07/2020] [Accepted: 09/13/2020] [Indexed: 05/18/2023]
Abstract
Corneal biomechanics play a fundamental role in the genesis and progression of corneal pathologies, such as keratoconus; in corneal remodeling after corneal surgery; and in affecting the measurement accuracy of glaucoma biomarkers, such as the intraocular pressure (IOP). Air-puff induced corneal deformation imaging reveals information highlighting normal and pathological corneal response to a non-contact mechanical excitation. However, current commercial systems are limited to monitoring corneal deformation only on one corneal meridian. Here, we present a novel custom-developed swept-source optical coherence tomography (SSOCT) system, coupled with a collinear air-puff excitation, capable of acquiring dynamic corneal deformation on multiple meridians. Backed by numerical simulations of corneal deformations, we propose two different scan patterns, aided by low coil impedance galvanometric scan mirrors that permit an appropriate compromise between temporal and spatial sampling of the corneal deformation profiles. We customized the air-puff module to provide an unobstructed SSOCT field of view and different peak pressures, air-puff durations, and distances to the eye. We acquired multi-meridian corneal deformation profiles (a) in healthy human eyes in vivo, (b) in porcine eyes ex vivo under varying controlled IOP, and (c) in a keratoconus-mimicking porcine eye ex vivo. We detected deformation asymmetries, as predicted by numerical simulations, otherwise missed on a single meridian that will substantially aid in corneal biomechanics diagnostics and pathology screening.
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Affiliation(s)
- Andrea Curatolo
- Instituto de Óptica “Daza de Valdés”,
Consejo Superior de Investigaciones Científicas (IO, CSIC), Madrid,
Spain
| | - Judith S. Birkenfeld
- Instituto de Óptica “Daza de Valdés”,
Consejo Superior de Investigaciones Científicas (IO, CSIC), Madrid,
Spain
| | - Eduardo Martinez-Enriquez
- Instituto de Óptica “Daza de Valdés”,
Consejo Superior de Investigaciones Científicas (IO, CSIC), Madrid,
Spain
| | - James A. Germann
- Instituto de Óptica “Daza de Valdés”,
Consejo Superior de Investigaciones Científicas (IO, CSIC), Madrid,
Spain
| | - Geethika Muralidharan
- Instituto de Óptica “Daza de Valdés”,
Consejo Superior de Investigaciones Científicas (IO, CSIC), Madrid,
Spain
| | | | - Daniel Pascual
- Instituto de Óptica “Daza de Valdés”,
Consejo Superior de Investigaciones Científicas (IO, CSIC), Madrid,
Spain
| | - Ashkan Eliasy
- Biomechanical Engineering Group, University
of Liverpool, Liverpool, United
Kingdom
| | - Ahmed Abass
- Biomechanical Engineering Group, University
of Liverpool, Liverpool, United
Kingdom
| | - Jędrzej Solarski
- Physical Optics and Biophotonics Group,
Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw,
Poland
| | - Karol Karnowski
- Physical Optics and Biophotonics Group,
Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw,
Poland
| | - Maciej Wojtkowski
- Physical Optics and Biophotonics Group,
Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw,
Poland
| | - Ahmed Elsheikh
- Biomechanical Engineering Group, University
of Liverpool, Liverpool, United
Kingdom
- Beijing Advanced Innovation Centre for
Biomedical Engineering, Beihang University, Beijing, China
- NIHR Biomedical Research Centre for
Ophthalmology, Moorfields Eye Hospital, NHS Foundation Trust, and UCL
Institute of Ophthalmology, United
Kingdom
| | - Susana Marcos
- Instituto de Óptica “Daza de Valdés”,
Consejo Superior de Investigaciones Científicas (IO, CSIC), Madrid,
Spain
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21
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Masiwa LE, Moodley V. A review of corneal imaging methods for the early diagnosis of pre-clinical Keratoconus. JOURNAL OF OPTOMETRY 2020; 13:269-275. [PMID: 31917136 PMCID: PMC7520528 DOI: 10.1016/j.optom.2019.11.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 10/22/2019] [Accepted: 11/09/2019] [Indexed: 05/15/2023]
Abstract
BACKGROUND Keratoconus (KC) is a corneal ectasia characterised by steepening corneal curvature, changes in refractive error and corneal thickness that result in visual impairment. Early signs of KC include displacement of the thinnest part of the cornea from the central position, changes in the corneal epithelial layer cell distribution, variations in the anterior corneal astigmatism/posterior corneal astigmatism relationship and a variation in corneal thickness. It is important that we review the corneal imaging methods for the diagnosis of preclinical KC. METHOD An online literature search was carried out on PubMed. Only publications detailing corneal assessment procedures were considered for this review and any publication on instruments that did not generate KC predictability indices were also excluded from the review. The 308 publications were reviewed. DISCUSSION Corneal assessment techniques, with the ability to characterise both the anterior and posterior corneal surfaces, are invaluable in the diagnosis of pre-clinical KC. Reflection based and elevation based corneal imaging systems should be used in conjunction with other assessments such as higher order aberration measuring systems to improve sensitivity and reliability in the diagnosis of pre-clinical KC. Ultra high resolution ultrasound can detect pre-clinical KC. The ability to asses both the epithelium and endothelium makes anterior surface optical coherence tomography a superior technique for pre-clinical KC diagnosis. There is a positive correlation between central corneal thickness and corneal hysteresis. Corneal biomechanics should be considered in conjunction with other corneal assessments in the diagnosis of pre-clinical KC.
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Affiliation(s)
- Lynett Erita Masiwa
- Department of Ophthalmology, University of Zimbabwe, College of Health Sciences, P. O. Box A178, Avondale, Harare, Zimbabwe.
| | - Vanessa Moodley
- School of Health Sciences, Department of Optometry, University of Kwazulu Natal, Durban, South Africa
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Nair A, Singh M, Aglyamov SR, Larin KV. Heartbeat OCE: corneal biomechanical response to simulated heartbeat pulsation measured by optical coherence elastography. JOURNAL OF BIOMEDICAL OPTICS 2020; 25:1-9. [PMID: 32372574 PMCID: PMC7199791 DOI: 10.1117/1.jbo.25.5.055001] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Accepted: 04/24/2020] [Indexed: 05/04/2023]
Abstract
SIGNIFICANCE It is generally agreed that the corneal mechanical properties are strongly linked to many eye diseases and could be used to assess disease progression and response to therapies. Elastography is the most notable method of assessing corneal mechanical properties, but it generally requires some type of external excitation to induce a measurable displacement in the tissue. AIM We present Heartbeat Optical Coherence Elastography (Hb-OCE), a truly passive method that can measure the elasticity of the cornea based on intrinsic corneal displacements induced by the heartbeat. APPROACH Hb-OCE measurements were performed in untreated and UV-A/riboflavin cross-linked porcine corneas ex vivo, and a distinct difference in strain was detected. Furthermore, a partially cross-linked cornea was also assessed, and the treated and untreated areas were similarly distinguished. RESULTS Our results suggest that Hb-OCE can spatially map displacements in the cornea induced by small fluctuations in intraocular pressure, similar to what is induced by the heartbeat. CONCLUSIONS The described technique opens the possibility for completely passive and noncontact in vivo assessment of corneal stiffness.
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Affiliation(s)
- Achuth Nair
- University of Houston, Department of Biomedical Engineering, Houston, Texas, United States
| | - Manmohan Singh
- University of Houston, Department of Biomedical Engineering, Houston, Texas, United States
| | - Salavat R. Aglyamov
- University of Houston, Department of Mechanical Engineering, Houston, Texas, United States
| | - Kirill V. Larin
- University of Houston, Department of Biomedical Engineering, Houston, Texas, United States
- Address all correspondence to Kirill V. Larin, E-mail:
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Corneal pulsation and biomechanics during induced ocular pulse. An ex-vivo pilot study. PLoS One 2020; 15:e0228920. [PMID: 32053692 PMCID: PMC7018024 DOI: 10.1371/journal.pone.0228920] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Accepted: 01/15/2020] [Indexed: 01/16/2023] Open
Abstract
The purpose of this study was to ascertain the relationships between the amplitude of the corneal pulse (CP) signal and the parameters of corneal biomechanics during ex-vivo intraocular pressure (IOP) elevation experiments on porcine eyes with artificially induced ocular pulse cycles. Two experiments were carried out using porcine eyes. In the first one, a selected eye globe was subjected to three IOP levels (15, 30 and 45 mmHg), where changes in physical ocular pulse amplitude were controlled by infusion/withdrawal volumes (ΔV). In the second experiment, six eyes were subjected to IOP from 15 mmHg to 45 mmHg in steps of 5 mmHg with a constant ΔV, where corneal deformation parameters were measured using Corvis ST. In both experiments, at each IOP, the CP and IOP signals were acquired synchronically using a non-contact ultrasonic distance sensor and a pressure transmitter, respectively. Based on the amplitudes of the CP and IOP signals ocular pulse based corneal rigidity index (OPCRI) was calculated. Results indicate positive correlations between ΔV and the physical ocular pulse amplitude, and between ΔV and the corneal pulse amplitude (both p < 0.001). OPCRI was found to increase with elevated IOP. Furthermore, IOP statistically significantly differentiated changes in OPCRI, the amplitudes of CP and IOP signals and in most of the corneal deformation parameters (p < 0.05). The partial correlation analysis, with IOP as a control variable, revealed a significant correlation between the length of the flattened cornea during the first applanation (A1L) and the corneal pulse amplitude (p = 0.002), and between A1L and OPCRI (p = 0.003). In conclusion, this study proved that natural corneal pulsations, detected with a non-contact ultrasonic technique, reflect pressure-volume dynamics and can potentially be utilized to assess stiffness of the cornea. The proposed new rigidity index could be a simple approach to estimating corneal rigidity.
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24
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Pye DC. A clinical method for estimating the modulus of elasticity of the human cornea in vivo. PLoS One 2020; 15:e0224824. [PMID: 31914133 PMCID: PMC6948750 DOI: 10.1371/journal.pone.0224824] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Accepted: 10/22/2019] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND To develop a method, using current clinical instrumentation, to estimate the Young's modulus of the human cornea in vivo. METHODS Central corneal curvature (CCC), central corneal thickness(CCT), intraocular pressure (IOP) was measured with the Goldmann tonometer (IOPG) and the Pascal Dynamic Corneal Tonometer(PDCT) in one eye of 100 normal young human subjects (21.07 ± 2.94 years) in vivo. The Orssengo and Pye algorithm was used to calculate the Young's modulus of the corneas of these subjects. RESULTS The Young's modulus(E) of the corneas of the subjects using the PDCT and IOPG results (Ecalc) was 0.25 ± 0.10MPa, and without the PDCT results (Eiopg) was 0.29 ± 0.06MPa. The difference in these results is due to the difference in tonometry results between the two instruments, as the mean PDCT result for the subjects was 16.89 ± 2.49mmHg and the IOPG result 15.06 ± 2.71mmHg. E was affected by the CCC of the subjects but more particularly by the CCT and IOP measurements. Corneal stiffness results are also presented. CONCLUSION Two methods have been developed to estimate the Young's modulus of the human cornea in vivo using current clinical instrumentation. One method (Ecalc) is applicable to the general corneal condition, and Eiopg to the normal cornea, and these results can be used to calculate corneal stiffness.
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Affiliation(s)
- David C. Pye
- School of Optometry and Vision Science, University of New South Wales, Sydney, Australia
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25
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Nguyen BA, Reilly MA, Roberts CJ. Biomechanical contribution of the sclera to dynamic corneal response in air-puff induced deformation in human donor eyes. Exp Eye Res 2019; 191:107904. [PMID: 31883460 DOI: 10.1016/j.exer.2019.107904] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 12/18/2019] [Accepted: 12/24/2019] [Indexed: 02/01/2023]
Abstract
This study was conducted to evaluate the impact of varying scleral material properties on the biomechanical response of the cornea under air-puff induced deformation. Twenty pairs of human donor eyes were obtained for this study. One eye from each pair had its sclera stiffened using 4% glutaraldehyde, while the fellow eye served as control for uniaxial strip testing. The whole globes were mounted in a rigid holder and intraocular pressure (IOP) was set using a saline column. Dynamic corneal response parameters were measured before and after scleral stiffening using the CorVis ST, a dynamic Scheimpflug analyzer. IOP was set to 10, 20, 30, and 40 mmHg, with at least 3 examinations performed at each pressure step. Uniaxial tensile testing data were fit to a neo-Hookean model to estimate the Young's modulus of treated and untreated sclera. Scleral Young's modulus was found to be significantly correlated with several response parameters, including Highest Concavity Deformation Amplitude, Peak Distance, Highest Concavity Radius, and Stiffness Parameter-Highest Concavity (SP-HC). There were significant increases in SP-HC after scleral stiffening at multiple levels of IOP, while no significant difference was observed in the corneal Stiffness Parameter - Applanation 1 (SP-A1) at any level of IOP. Scleral mechanical properties significantly influenced the corneal deformation response to an air-puff. The stiffer the sclera, the greater the constraining effect on corneal deformation resulting in lower displaced amplitude. This may have important clinical implications and suggests that both corneal and scleral material properties contribute to the observed corneal response in air-puff induced deformation.
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Affiliation(s)
- B Audrey Nguyen
- Department of Biomedical Engineering, 1080 Carmack Rd, 270 Bevis Hall, The Ohio State University, Columbus, OH, USA
| | - Matthew A Reilly
- Department of Biomedical Engineering, 1080 Carmack Rd, 270 Bevis Hall, The Ohio State University, Columbus, OH, USA; Department of Ophthalmology & Visual Science, William H. Havener Eye Institute, 915 Olentangy River Rd, Suite, 5000, The Ohio State University, Columbus, OH, USA
| | - Cynthia J Roberts
- Department of Biomedical Engineering, 1080 Carmack Rd, 270 Bevis Hall, The Ohio State University, Columbus, OH, USA; Department of Ophthalmology & Visual Science, William H. Havener Eye Institute, 915 Olentangy River Rd, Suite, 5000, The Ohio State University, Columbus, OH, USA.
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26
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Kirby MA, Zhou K, Pitre JJ, Gao L, Li D, Pelivanov I, Song S, Li C, Huang Z, Shen T, Wang R, O’Donnell M. Spatial resolution in dynamic optical coherence elastography. JOURNAL OF BIOMEDICAL OPTICS 2019; 24:1-16. [PMID: 31535538 PMCID: PMC6749618 DOI: 10.1117/1.jbo.24.9.096006] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2019] [Accepted: 08/26/2019] [Indexed: 05/03/2023]
Abstract
Dynamic optical coherence elastography (OCE) tracks elastic wave propagation speed within tissue, enabling quantitative three-dimensional imaging of the elastic modulus. We show that propagating mechanical waves are mode converted at interfaces, creating a finite region on the order of an acoustic wavelength where there is not a simple one-to-one correspondence between wave speed and elastic modulus. Depending on the details of a boundary’s geometry and elasticity contrast, highly complex propagating fields produced near the boundary can substantially affect both the spatial resolution and contrast of the elasticity image. We demonstrate boundary effects on Rayleigh waves incident on a vertical boundary between media of different shear moduli. Lateral resolution is defined by the width of the transition zone between two media and is the limit at which a physical inclusion can be detected with full contrast. We experimentally demonstrate results using a spectral-domain OCT system on tissue-mimicking phantoms, which are replicated using numerical simulations. It is shown that the spatial resolution in dynamic OCE is determined by the temporal and spatial characteristics (i.e., bandwidth and spatial pulse width) of the propagating mechanical wave. Thus, mechanical resolution in dynamic OCE inherently differs from the optical resolution of the OCT imaging system.
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Affiliation(s)
- Mitchell A. Kirby
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - Kanheng Zhou
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
- University of Dundee, School of Science and Engineering, Dundee, United Kingdom
| | - John J. Pitre
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - Liang Gao
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - David Li
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
- University of Washington, Department of Chemical Engineering, Seattle, Washington, United States
| | - Ivan Pelivanov
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
- Address all correspondence to Ivan Pelivanov, E-mail:
| | - Shaozhen Song
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - Chunhui Li
- University of Dundee, School of Science and Engineering, Dundee, United Kingdom
| | - Zhihong Huang
- University of Dundee, School of Science and Engineering, Dundee, United Kingdom
| | - Tueng Shen
- University of Washington, Department of Ophthalmology, Seattle, Washington, United States
| | - Ruikang Wang
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
- University of Washington, Department of Ophthalmology, Seattle, Washington, United States
| | - Matthew O’Donnell
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
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27
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Consejo A, Glawdecka K, Karnowski K, Solarski J, Rozema JJ, Wojtkowski M, Iskander DR. Corneal Properties of Keratoconus Based on Scheimpflug Light Intensity Distribution. ACTA ACUST UNITED AC 2019; 60:3197-3203. [DOI: 10.1167/iovs.19-26963] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- Alejandra Consejo
- Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland
| | - Karolina Glawdecka
- Department of Biomedical Engineering, Wroclaw University of Science and Technology, Wroclaw, Poland
| | - Karol Karnowski
- Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland
- School of Electrical, Electronic and Computer Engineering, The University of Western Australia, Perth, Australia
| | - Jedrzej Solarski
- Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland
| | - Jos J. Rozema
- Department of Ophthalmology, Antwerp University Hospital, Edegem, Belgium
- Department of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium
| | - Maciej Wojtkowski
- Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland
| | - D. Robert Iskander
- Department of Biomedical Engineering, Wroclaw University of Science and Technology, Wroclaw, Poland
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28
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Shao P, Eltony AM, Seiler TG, Tavakol B, Pineda R, Koller T, Seiler T, Yun SH. Spatially-resolved Brillouin spectroscopy reveals biomechanical abnormalities in mild to advanced keratoconus in vivo. Sci Rep 2019; 9:7467. [PMID: 31097778 PMCID: PMC6522517 DOI: 10.1038/s41598-019-43811-5] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 04/27/2019] [Indexed: 12/27/2022] Open
Abstract
Mounting evidence connects the biomechanical properties of tissues to the development of eye diseases such as keratoconus, a disease in which the cornea thins and bulges into a conical shape. However, measuring biomechanical changes in vivo with sufficient sensitivity for disease detection has proven challenging. Here, we demonstrate the diagnostic potential of Brillouin light-scattering microscopy, a modality that measures longitudinal mechanical modulus in tissues with high measurement sensitivity and spatial resolution. We have performed a study of 85 human subjects (93 eyes), consisting of 47 healthy volunteers and 38 keratoconus patients at differing stages of disease, ranging from stage I to stage IV. The Brillouin data in vivo reveal increasing biomechanical inhomogeneity in the cornea with keratoconus progression and biomechanical asymmetry between the left and right eyes at the onset of keratoconus. The receiver operating characteristic analysis of the stage-I patient data indicates that mean Brillouin shift of the cone performs better than corneal thickness and maximum curvature respectively. In conjunction with morphological patterns, Brillouin microscopy may add value for diagnosis of keratoconus and potentially for screening subjects at risk of complications prior to laser eye surgeries.
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Affiliation(s)
- Peng Shao
- Harvard Medical School and Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA, 02114, USA
| | - Amira M Eltony
- Harvard Medical School and Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA, 02114, USA
| | - Theo G Seiler
- Harvard Medical School and Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA, 02114, USA.,Institute for Refractive and Ophthalmic Surgery (IROC), Zürich, 8002, Switzerland.,Universitätsklinik für Augenheilkunde, Inselspital, Bern, 3010, Switzerland
| | - Behrouz Tavakol
- Harvard Medical School and Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA, 02114, USA
| | - Roberto Pineda
- Massachusetts Eye and Ear Infirmary, Boston, MA, 02114, USA
| | - Tobias Koller
- Institute for Refractive and Ophthalmic Surgery (IROC), Zürich, 8002, Switzerland
| | - Theo Seiler
- Institute for Refractive and Ophthalmic Surgery (IROC), Zürich, 8002, Switzerland.
| | - Seok-Hyun Yun
- Harvard Medical School and Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA, 02114, USA. .,Harvard-MIT Health Sciences and Technology, Cambridge, MA, 02139, USA.
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29
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Vroemen PAMM, Gorgels TGMF, Webers CAB, de Boer J. Modeling the Mechanical Parameters of Glaucoma. TISSUE ENGINEERING PART B-REVIEWS 2019; 25:412-428. [PMID: 31088331 DOI: 10.1089/ten.teb.2019.0044] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Glaucoma is a major eye disease characterized by a progressive loss of retinal ganglion cells (RGCs). Biomechanical forces as a result of hydrostatic pressure and strain play a role in this disease. Decreasing intraocular pressure is the only available therapy so far, but is not always effective and does not prevent blindness in many cases. There is a need for drugs that protect RGCs from dying in glaucoma; to develop these, we need valid glaucoma and drug screening models. Since in vivo models are unsuitable for screening purposes, we focus on in vitro and ex vivo models in this review. Many groups have studied pressure and strain model systems to mimic glaucoma, to investigate the molecular and cellular events leading to mechanically induced RGC death. Therefore, the focus of this review is on the different mechanical model systems used to mimic the biomechanical forces in glaucoma. Most models use either cell or tissue strain, or fluid- or gas-controlled hydrostatic pressure application and apply it to the relevant cell types such as trabecular meshwork cells, optic nerve head astrocytes, and RGCs, but also to entire eyes. New model systems are warranted to study concepts and test experimental compounds for the development of new drugs to protect vision in glaucoma patients. Impact Statement The outcome of currently developed models to investigate mechanically induced retinal ganglion cell death by applying different mechanical strains varies widely. This suggests that a robust glaucoma model has not been developed yet. However, a comprehensive overview of current developments is not available. In this review, we have therefore assessed what has been done before and summarized the available knowledge in the field, which can be used to develop improved models for glaucoma research.
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Affiliation(s)
- Pascal A M M Vroemen
- University Eye Clinic Maastricht UMC+, Maastricht University Medical Centre+, Maastricht, The Netherlands.,Department of Complex Tissue Regeneration (CTR), MERLN Institute for Technology-Inspired Regenerative Medicine, Maastricht University, Maastricht, The Netherlands.,Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - Theo G M F Gorgels
- University Eye Clinic Maastricht UMC+, Maastricht University Medical Centre+, Maastricht, The Netherlands.,Netherlands Institute for Neuroscience, Amsterdam, The Netherlands
| | - Carroll A B Webers
- University Eye Clinic Maastricht UMC+, Maastricht University Medical Centre+, Maastricht, The Netherlands
| | - Jan de Boer
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.,Institute for Complex Molecular Structures, Eindhoven University of Technology, Eindhoven, The Netherlands
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30
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Coppola S, Schmidt T, Ruocco G, Antonacci G. Quantifying cellular forces and biomechanical properties by correlative micropillar traction force and Brillouin microscopy. BIOMEDICAL OPTICS EXPRESS 2019; 10:2202-2212. [PMID: 31149370 PMCID: PMC6524592 DOI: 10.1364/boe.10.002202] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 02/18/2019] [Accepted: 02/19/2019] [Indexed: 06/09/2023]
Abstract
Cells sense and respond to external physical forces and substrate rigidity by regulating their cell shape, internal cytoskeletal tension, and stiffness. Here we show that the combination of micropillar traction force and noncontact Brillouin microscopy provides access to cell-generated forces and intracellular mechanical properties at optical resolution. Actin-rich cytoplasmic domains of 3T3 fibroblasts showed significantly higher Brillouin shifts, indicating a potential increase in stiffness when adhering on fibronectin-coated glass compared to soft PDMS micropillars. Our findings demonstrate the complementarity of micropillar traction force and Brillouin microscopy to better understand the relation between cell force generation and the intracellular mechanical properties.
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Affiliation(s)
- Stefano Coppola
- Physics of Life Processes - Kamerlingh Onnes-Huygens Laboratory, Leiden Institute of Physics, Leiden University, Leiden,
The Netherlands
| | - Thomas Schmidt
- Physics of Life Processes - Kamerlingh Onnes-Huygens Laboratory, Leiden Institute of Physics, Leiden University, Leiden,
The Netherlands
| | - Giancarlo Ruocco
- Center for Life Nano Science @Sapienza, Istituto Italiano di Tecnologia, Rome,
Italy
| | - Giuseppe Antonacci
- Center for Life Nano Science @Sapienza, Istituto Italiano di Tecnologia, Rome,
Italy
- Photonics Research Group, Ghent University - imec, Ghent,
Belgium
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31
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Brazile BL, Hua Y, Jan NJ, Wallace J, Gogola A, Sigal IA. Thin Lamina Cribrosa Beams Have Different Collagen Microstructure Than Thick Beams. Invest Ophthalmol Vis Sci 2019; 59:4653-4661. [PMID: 30372734 PMCID: PMC6149225 DOI: 10.1167/iovs.18-24763] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Purpose To compare the collagen microstructural crimp characteristics between thin and thick lamina cribrosa (LC) beams. Methods Seven eyes from four sheep were fixed at 5 mm Hg IOP in 10% formalin. For each eye, one to three coronal cryosections through the LC were imaged with polarized light microscopy and analyzed to visualize the LC and determine collagen fiber microstructure. For every beam, we measured its width and three characteristics of the crimp of its collagen fibers: waviness, tortuosity, and amplitude. Linear mixed effects models were used to test whether crimp characteristics were associated with the LC beam width. Results For each eye and over all the eyes, LC beam width was positively associated with crimp waviness and tortuosity, and negatively associated with crimp amplitude (P's < 0.0001). Thin beams, average width 13.11 μm, had average (SD) waviness, tortuosity, and amplitude of 0.27 (0.17) radians, 1.017 (0.028) and 1.88 (1.41) μm, respectively. For thick beams, average width 26.10 μm, these characteristics were 0.33 (0.18) radians, 1.025 (0.037) and 1.58 (1.36) μm, respectively. Conclusions Our results suggest heterogeneity in LC beam mechanical properties. Thin beams were less wavy than their thicker counterparts, suggesting that thin beams may stiffen at lower IOP than thick beams. This difference may allow thin beams to support similar amounts of IOP-induced force as thicker beams, thus providing a similar level of structural support to the axons at physiologic IOP, despite the differences in width. Measurements of beam-level mechanical properties are needed to confirm these predictions.
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Affiliation(s)
- Bryn L Brazile
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
| | - Yi Hua
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
| | - Ning-Jiun Jan
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States.,Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Jacob Wallace
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
| | - Alexandra Gogola
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
| | - Ian A Sigal
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States.,Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States.,McGowan Institute for Regenerative Medicine, University of Pittsburgh School of Medicine and University of Pittsburgh, Pittsburgh, Pennsylvania, United States.,The Louis J. Fox Center for Vision Restoration of UPMC and the University of Pittsburgh, Pittsburgh, Pennsylvania, United States
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32
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Duan XJ, Jefferys JL, Quigley HA. Evaluation of Automated Segmentation Algorithms for Optic Nerve Head Structures in Optical Coherence Tomography Images. Invest Ophthalmol Vis Sci 2019; 59:3816-3826. [PMID: 30073355 DOI: 10.1167/iovs.18-24469] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To compare the identification of optic nerve head (ONH) structures in optical coherence tomography images by observers and automated algorithms. Methods ONH images in 24 radial scan sets by optical coherence tomography were obtained in 51 eyes of 29 glaucoma patients and suspects. Masked intraobserver and interobserver comparisons were made of marked endpoints of Bruch's membrane opening (BMO) and the anterior lamina cribrosa (LC). BMO and LC positional markings were compared between observer and automated algorithm. Repeated analysis on 20 eyes by the algorithm was compared. Regional ONH data were derived from the algorithms. Results Intraobserver difference in BMO width was not significantly different from zero (P ≥ 0.32) and the difference in LC position was less than 1% different (P = 0.04). Interobserver were slightly larger than intraobserver differences, but interobserver BMO width difference was 0.36% (P = 0.63). Mean interobserver difference in LC position was 14.74 μm (P = 0.004), 3% of the typical anterior lamina depth (ALD). Between observer and algorithm, BMO width differed by 1.85% (P = 0.23) and mean LC position was not significantly different (3.77 μm, P = 0.77). Repeat algorithmic analysis had a mean difference in BMO area of 0.38% (P = 0.47) and mean ALD difference of 0.54 ± 0.72%. Regional ALD had greater variability in the horizontal ONH regions. Some individual outlier images were not validly marked by either observers or algorithm. Conclusions Automated identification of ONH structures is comparable to observer markings for BMO and anterior LC position, making BMO a practical reference plane for algorithmic analysis.
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Affiliation(s)
- Xiangyun J Duan
- The Glaucoma Center of Excellence, Wilmer Ophthalmological Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - Joan L Jefferys
- The Glaucoma Center of Excellence, Wilmer Ophthalmological Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - Harry A Quigley
- The Glaucoma Center of Excellence, Wilmer Ophthalmological Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
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33
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Momeni-Moghaddam H, Hashemi H, Zarei-Ghanavati S, Ostadimoghaddam H, Yekta A, Aghamirsalim M, Khabazkhoob M. Four-year changes in corneal biomechanical properties in children. Clin Exp Optom 2019; 102:489-495. [PMID: 30887574 DOI: 10.1111/cxo.12890] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Revised: 12/26/2018] [Accepted: 02/05/2019] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND To determine four-year changes of corneal biomechanical parameters in Iranian children aged seven to eleven years and their correlation with optical components. METHODS In this four-year prospective cohort study, 468 children aged seven to eleven years who were initially evaluated in 2012 were re-evaluated in 2016-2017. Multi-stage stratified cluster sampling was applied. Cycloplegic refraction, biometry using LENSTAR/BioGraph, and corneal biomechanical assessment using Ocular Response Analyzer (ORA) were undertaken for each participant. The corneal biomechanical parameters assessed were corneal hysteresis (CH), corneal resistance factor (CRF), areas under the peaks 1 and 2 (p1 and p2 areas) and irregularity indices (A and B indices). RESULTS All biomechanical parameters except A index decreased in phase 2. The mean changes of CH and CRF were 0.68 ± 0.16 mmHg (for both parameters) during four years. The mean difference in CH and CRF was 0.23 ± 0.23 and 0.24 ± 0.23 mmHg in females and 1.03 ± 0.23 and 0.96 ± 0.23 mmHg in males, respectively. Different age groups showed varying amounts of decrease in all parameters except for A index. The age group 'ten years' experienced the smallest decrease in CH (0.02 ± 0.48 mmHg) and CRF (0.20 ± 0.47 mmHg) and the age group 'eleven years' showed the greatest decrease in CH (1.41 ± 0.35 mmHg) and CRF (0.99 ± 0.34 mmHg). According to linear regression analysis, CH and CRF had a significant direct relationship with corneal power and an inverse relationship with axial length (p < 0.001). CONCLUSION Age and sex are influencing factors on the ORA parameters. Older age is associated with reduced biomechanical parameters and reductions are more significant in males than females. Axial elongation and corneal flattening decrease CH and CRF.
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Affiliation(s)
- Hamed Momeni-Moghaddam
- Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Hassan Hashemi
- Noor Research Center for Ophthalmic Epidemiology, Noor Eye Hospital, Tehran, Iran
| | | | - Hadi Ostadimoghaddam
- Refractive Errors Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Abbasali Yekta
- Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | | | - Mehdi Khabazkhoob
- Department of Medical Surgical Nursing, School of Nursing and Midwifery, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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Shao P, Seiler TG, Eltony AM, Ramier A, Kwok SJJ, Scarcelli G, Ii RP, Yun SH. Effects of Corneal Hydration on Brillouin Microscopy In Vivo. Invest Ophthalmol Vis Sci 2019; 59:3020-3027. [PMID: 30025137 PMCID: PMC5995485 DOI: 10.1167/iovs.18-24228] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Purpose To investigate how corneal hydration affects the Brillouin frequency of corneal stroma. Methods From a simple analytical model considering the volume fraction of water in corneal stroma, we derived the dependence of Brillouin frequency on hydration and hydration-induced corneal thickness variation. The Brillouin frequencies of fresh ex vivo porcine corneas were measured as their hydration was varied in dextran solution and water. Healthy volunteers (8 eyes) were scanned in vivo repeatedly over the course of 9 hours, and the diurnal variations of Brillouin frequency and central corneal thickness (CCT) were measured. Results The measured dependence of Brillouin frequency on hydration, both ex vivo and in vivo, agreed well with the theoretical prediction. The Brillouin frequencies of human corneas scanned immediately after waking were on average ∼25 MHz lower than their daytime average values. For stabilized corneas, the typical variation of Brillouin frequency was ± 7.2 MHz. With respect to CCT increase or swelling, the Brillouin frequency decreased with a slope of −1.06 MHz/μm in vivo. Conclusions The ex vivo and in vivo data agree with our theoretical model and support that the effect of corneal hydration on Brillouin frequency comes predominantly from the dependence of the tissue compressibility on the water. Corneal hydration correlates negatively with the Brillouin frequency. During daytime activities, the influence of physiological hydration changes in human corneas is < ± 10 MHz. The sensitivity to hydration may potentially be useful in detecting abnormal hydration change in patients with endothelial disorders.
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Affiliation(s)
- Peng Shao
- Wellman Center for Photomedicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States
| | - Theo G Seiler
- Wellman Center for Photomedicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States.,Institut für Refraktive und Ophthalmo-Chirurgie (IROC), Zürich, Switzerland.,Universitätsklinik für Augenheilkunde, Inselspital, Bern, Switzerland
| | - Amira M Eltony
- Wellman Center for Photomedicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States
| | - Antoine Ramier
- Wellman Center for Photomedicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States.,Harvard-MIT Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
| | - Sheldon J J Kwok
- Wellman Center for Photomedicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States.,Harvard-MIT Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
| | - Giuliano Scarcelli
- Wellman Center for Photomedicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States.,Fischell Department of Bioengineering, University of Maryland, College Park, Maryland, United States
| | - Roberto Pineda Ii
- Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, United States
| | - Seok-Hyun Yun
- Wellman Center for Photomedicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States.,Harvard-MIT Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States.,Department of Dermatology, Harvard Medical School, Boston, Massachusetts, United States
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Nguyen BA, Roberts CJ, Reilly MA. Biomechanical Impact of the Sclera on Corneal Deformation Response to an Air-Puff: A Finite-Element Study. Front Bioeng Biotechnol 2019; 6:210. [PMID: 30687701 PMCID: PMC6335394 DOI: 10.3389/fbioe.2018.00210] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Accepted: 12/18/2018] [Indexed: 01/18/2023] Open
Abstract
Aim or Purpose: To describe the effect of varying scleral stiffness on the biomechanical deformation response of the cornea under air-puff loading via a finite-element (FE) model. Methods: A two-dimensional axisymmetric stationary FE model of the whole human eye was used to examine the effects varying scleral stiffness and intraocular pressure (IOP) on the maximum apical displacement of the cornea. The model was comprised of the cornea, sclera, vitreous, and surrounding air region. The velocity and pressure profiles of an air-puff from a dynamic Scheimpflug analyzer were replicated in the FE model, and the resultant profile was applied to deform the cornea in a multiphysics study (where the air-puff was first simulated before being applied to the corneal surface). IOP was simulated as a uniform pressure on the globe interior. The simulation results were compared to data from ex vivo scleral stiffening experiments with human donor globes. Results: The FE model predicted decreased maximum apical displacement with increased IOP and increased ratio of scleral-to-corneal Young's moduli. These predictions were in good agreement (within one standard deviation) with findings from ex vivo scleral stiffening experiments using human donor eyes. These findings demonstrate the importance of scleral material properties on the biomechanical deformation response of the cornea in air-puff induced deformation. Conclusion: The results of an air-puff induced deformation are often considered to be solely due to IOP and corneal properties. The current study showed that the stiffer the sclera, the greater will be the limitation on corneal deformation, separately from IOP. This may have important clinical implications to interpreting the response of the cornea under air-puff loading in pathologic conditions.
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Affiliation(s)
- B. Audrey Nguyen
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States
| | - Cynthia J. Roberts
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States
- Department of Ophthalmology & Visual Science, The Ohio State University, Columbus, OH, United States
| | - Matthew A. Reilly
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States
- Department of Ophthalmology & Visual Science, The Ohio State University, Columbus, OH, United States
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Lin X, Naidu RK, Dai J, Zhou X, Qu X, Zhou H. Scleral Cross-Linking Using Glyceraldehyde for the Prevention of Axial Elongation in the Rabbit: Blocked Axial Elongation and Altered Scleral Microstructure. Curr Eye Res 2018; 44:162-171. [PMID: 30222005 DOI: 10.1080/02713683.2018.1522647] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
BACKGROUND This study aims to assess the efficacy of the scleral collagen cross-linking method using glyceraldehyde solution for prevention of lens-induced axial elongation in New Zealand rabbits and investigate the biochemical and microstructural changes that occur. METHODS The right eyes of New Zealand rabbits aged seven weeks were randomly divided into three groups: the cross-linking group (n = 6), non-crosslinking group (n = 5), and untreated control group (n = 5). Eyes in cross-linking and non-crosslinking groups were treated with a -8.00 Diopter spherical lens over the course of two weeks. The cross-linking effects were achieved by a sub-Tenon's injection of 0.15 ml 0.5 M glyceraldehyde to eyes in the CL group. Ocular parameters were measured on the 1st, 7th, and 14th days. Biomechanical testing, light and electronic microscopy were used. RESULTS Following the cross-linking treatment, eyes in the cross-linking group had a shorter axial length compared to those in the non-crosslinking group (p = 0.006). Collagen fibrils larger than 240 nm were observed in the scleral stroma of cross-linking group, which were absent in the scleral stroma of the non-crosslinking and untreated control group. The mean ultimate stress and Young's modulus was significantly greater in the cross-linking group compared to those in the non-crosslinking and untreated control group (p < 0.05). No histological damage observed in the retina or choroid. CONCLUSIONS This study demonstrates that lens-induced axial elongation in rabbits can be effectively blocked by cross-linking using glyceraldehyde, with anatomical and mechanical modification and no deleterious effects.
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Affiliation(s)
- Xiao Lin
- a Department of Ophthalmology & Visual Science , Fudan University Eye Ear Nose and Throat Hospital, Shanghai Medical College, Fudan University , Shanghai , China.,b Key Laboratory of Myopia, Ministry of Health , Fudan University , Shanghai , China.,c Shanghai Key Laboratory of Visual Impairment and Restoration , Fudan University , Shanghai , China
| | - Rajeev K Naidu
- d Concord Repatriation General Hospital , The University of Sydney , Camperdown , Australia
| | - Jinhui Dai
- a Department of Ophthalmology & Visual Science , Fudan University Eye Ear Nose and Throat Hospital, Shanghai Medical College, Fudan University , Shanghai , China.,b Key Laboratory of Myopia, Ministry of Health , Fudan University , Shanghai , China.,c Shanghai Key Laboratory of Visual Impairment and Restoration , Fudan University , Shanghai , China
| | - Xingtao Zhou
- a Department of Ophthalmology & Visual Science , Fudan University Eye Ear Nose and Throat Hospital, Shanghai Medical College, Fudan University , Shanghai , China.,b Key Laboratory of Myopia, Ministry of Health , Fudan University , Shanghai , China.,c Shanghai Key Laboratory of Visual Impairment and Restoration , Fudan University , Shanghai , China
| | - Xiaomei Qu
- a Department of Ophthalmology & Visual Science , Fudan University Eye Ear Nose and Throat Hospital, Shanghai Medical College, Fudan University , Shanghai , China.,b Key Laboratory of Myopia, Ministry of Health , Fudan University , Shanghai , China.,c Shanghai Key Laboratory of Visual Impairment and Restoration , Fudan University , Shanghai , China
| | - Hao Zhou
- a Department of Ophthalmology & Visual Science , Fudan University Eye Ear Nose and Throat Hospital, Shanghai Medical College, Fudan University , Shanghai , China.,b Key Laboratory of Myopia, Ministry of Health , Fudan University , Shanghai , China.,c Shanghai Key Laboratory of Visual Impairment and Restoration , Fudan University , Shanghai , China
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The Effect of Strabismus Muscle Surgery on Corneal Biomechanics. J Ophthalmol 2018; 2018:8072140. [PMID: 30305960 PMCID: PMC6165609 DOI: 10.1155/2018/8072140] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Accepted: 08/27/2018] [Indexed: 11/22/2022] Open
Abstract
Purpose Studying the early effect of different extraocular muscle (EOM) surgeries on corneal biomechanics. Subjects and methods This is a prospective, nonrandomized, interventional study, in which 42 eyes of 29 candidates for EOM surgery for strabismus correction at Cairo university hospitals, aged 14–37 years, were recruited. All participants had measuring of the visual acuity, refraction (spherical equivalent (SE)), assessment of the EOM motility and muscle balance, sensory evaluation, fundus examination, and assessing the ocular biomechanics using the Ocular response analyzer (ORA, Reichert, INC., Depew, NY) noting the corneal hysteresis (CH) and corneal resistance factor (CRF) preoperatively. Same patients were reassessed using ORA 4 weeks postoperatively following a different standard EOM surgery (recti weakening/strengthening and inferior oblique weakening either (graded recession) according to the surgical indication, and ∆CH and ∆CRF were calculated, each is the preoperative − the postoperative value. Results ∆CH and ∆CRF = −0.78 ± 1.56 and −0.72 ± 2.15, respectively, and a highly significant difference was found between each of the pre- and postoperative CH and CRF (p < 0.001). 18 eyes had single EOM surgery, while 24 had multiple (2 or 3) EOM surgery; ∆CH in the single group = −1.28 ± 1.5, and ∆CH in the multiple group = 0.4 ± 1.49 (p=0.07). 23 eyes had EOM weakening surgery, while 18 had combined weakening and strengthening EOM surgery: ∆CH in the weakening group = −1.24 ± 1.77 and ∆CH in combined group = −0.26 ± 1.07 (p=0.04). A nonsignificant difference was found for ∆CRF (p=0.53). Conclusion A different EOM surgery has an early tendency for increase of the postoperative CH specially for muscle weakening procedures (recti recession/inferior oblique muscle weakening).
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In vivo optic nerve head mechanical response to intraocular and cerebrospinal fluid pressure: imaging protocol and quantification method. Sci Rep 2018; 8:12639. [PMID: 30140057 PMCID: PMC6107503 DOI: 10.1038/s41598-018-31052-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 08/09/2018] [Indexed: 01/22/2023] Open
Abstract
This study presents a quantification method for the assessment of the optic nerve head (ONH) deformations of the living human eye under acute intraocular pressure (IOP) elevation and change of cerebrospinal fluid pressure (CSFP) with body position. One eye from a brain-dead organ donor with open-angle glaucoma was imaged by optical coherence tomography angiography during an acute IOP and CSFP elevation test. Volumetric 3D strain was computed by digital volume correlation. With increase in IOP the shear strain consistently increased in both sitting and supine position (p < 0.001). When CSFP was increased at constant IOP by changing body position, a global reduction in the ONH strain was observed (−0.14% p = 0.0264). Strain in the vasculature was significantly higher than in the structural tissue (+0.90%, p = 0.0002). Retinal nerve fiber layer (RNFL) thickness strongly associated (ρ = −0.847, p = 0.008) with strain in the peripapillary sclera (ppScl) but not in the retina (p = 0.433) and lamina (p = 0.611). These initial results show that: CSFP independently to IOP modulates strain in the human ONH; ppScl strains are greater than strains in lamina and retina; strain in the retinal vasculature was higher than in the structural tissue; In this glaucoma eye, higher ppScl strain associated with lower RNFL thickness.
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Abstract
PURPOSE OF REVIEW Assessment of corneal biomechanics has been an unmet clinical need in ophthalmology for many years. Many researchers and clinicians have identified corneal biomechanics as source of variability in refractive procedures and one of the main factors in keratoconus. However, it has been difficult to accurately characterize corneal biomechanics in patients. The recent development of Brillouin light scattering microscopy heightens the promise of bringing biomechanics into the clinic. The aim of this review is to overview the progress and discuss prospective applications of this new technology. RECENT FINDINGS Brillouin microscopy uses a low-power near-infrared laser beam to determine longitudinal modulus or mechanical compressibility of tissue by analyzing the return signal spectrum. Human clinical studies have demonstrated significant difference in the elastic properties of normal corneas versus corneas diagnosed with mild and severe keratoconus. Clinical data have also shown biomechanical changes after corneal cross-linking treatment of keratoconus patients. Brillouin measurements of the crystalline lens and sclera have also been demonstrated. SUMMARY Brillouin microscopy is a promising technology under commercial development at present. The technique enables physicians to characterize the biomechanical properties of ocular tissues.
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Affiliation(s)
- Seok Hyun Yun
- Harvard Medical School and Wellman Center for Photomedicine, Massachusetts General Hospital
| | - Dimitri Chernyak
- Intelon Optics Inc., Zero Emerson Place, Boston Massachusetts, USA
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40
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Man X, Arroyo E, Dunbar M, Reed DM, Shah N, Kagemann L, Kim W, Moroi SE, Argento A. Perilimbal sclera mechanical properties: Impact on intraocular pressure in porcine eyes. PLoS One 2018; 13:e0195882. [PMID: 29718942 PMCID: PMC5931674 DOI: 10.1371/journal.pone.0195882] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Accepted: 03/31/2018] [Indexed: 11/24/2022] Open
Abstract
There is extensive knowledge on the relationship of posterior scleral biomechanics and intraocular pressure (IOP) load on glaucomatous optic neuropathy; however, the role for biomechanical influence of the perilimbal scleral tissue on the aqueous humor drainage pathway, including the distal venous outflow system, and IOP regulation is not fully understood. The purpose of this work is to study the outflow characteristics of perfused porcine eyes relative to the biomechanical properties of the perilimbal sclera, the posterior sclera and the cornea. Enucleated porcine eyes from eleven different animals were perfused with surrogate aqueous at two fixed flow rates while monitoring their IOP. After perfusion, mechanical stress-strain and relaxation tests were conducted on specimens of perilimbal sclera, posterior sclera, and cornea from the same perfused eyes. Statistical analysis of the data demonstrated a strong correlation between increased tangent modulus of the perilimbal sclera tissues and increased perfusion IOP (R2 = 0.74, p = 0.0006 at lower flow rate and R2 = 0.71, p = 0.0011 at higher flow rate). In contrast, there were no significant correlations between IOP and the tangent modulus of the other tissues (Posterior sclera: R2 = 0.17 at lower flow rate and R2 = 0.30 at higher flow rate; cornea: R2 = 0.02 at lower flow rate and R2<0.01 at higher flow rate) nor the viscoelastic properties of any tissue (R2 ≤ 0.08 in all cases). Additionally, the correlation occurred for IOP and not net outflow facility (R2 ≤ 0.12 in all cases). These results provide new evidence that IOP in perfused porcine eyes is strongly influenced by the tangent modulus, sometimes called the tissue stiffness, of the most anterior portion of the sclera, i.e. the limbus.
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Affiliation(s)
- Xiaofei Man
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, Michigan, United States of America
- Department of Ophthalmology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, People’s Republic of China
| | - Elizabeth Arroyo
- Department of Mechanical Engineering, University of Michigan-Dearborn, Dearborn, Michigan, United States of America
| | - Martha Dunbar
- Department of Mechanical Engineering, University of Michigan-Dearborn, Dearborn, Michigan, United States of America
- Department of Mechanical Engineering, Northwestern University, Evanston, Illinois, United States of America
| | - David M. Reed
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Neil Shah
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, Michigan, United States of America
- Department of Ophthalmology, Loyola University Medical Center, Maywood, Illinois, United States of America
| | - Larry Kagemann
- Department of Ophthalmology, NYU Langone Medical Center, NYU School of Medicine, New York, New York, United States of America
- Division of Ophthalmic and Ear, Nose and Throat Devices, Office of Device Evaluation, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, Maryland, United States of America
| | - Wonsuk Kim
- Department of Mechanical Engineering, University of Michigan-Dearborn, Dearborn, Michigan, United States of America
| | - Sayoko E. Moroi
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Alan Argento
- Department of Mechanical Engineering, University of Michigan-Dearborn, Dearborn, Michigan, United States of America
- * E-mail:
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Pavlatos E, Chen H, Clayson K, Pan X, Liu J. Imaging Corneal Biomechanical Responses to Ocular Pulse Using High-Frequency Ultrasound. IEEE TRANSACTIONS ON MEDICAL IMAGING 2018; 37:663-670. [PMID: 29408793 PMCID: PMC5826553 DOI: 10.1109/tmi.2017.2775146] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Imaging corneal biomechanical changes or abnormalities is important for better clinical diagnosis and treatment of corneal diseases. We propose a novel ultrasound-based method, called ocular pulse elastography (OPE), to image corneal deformation during the naturally occurring ocular pulse. Experiments on animal and human donor eyes, as well as synthetic radiofrequency (RF) data, were used to evaluate the efficacy of the OPE method. Using very high-frequency ultrasound (center frequency = 55 MHz), correlation-based speckle tracking yielded an accuracy of less than 10% error for axial tissue displacements of or above. Satisfactory speckle tracking was achieved for out-of-plane displacements up to . Using synthetic RF data with or without a pre-defined uniform strain, the OPE method detected strains down to 0.0001 axially and 0.00025 laterally with an error less than 10%. Experiments in human donor eyes showed excellent repeatability with an intraclass correlation of 0.98. The measurement outcome from OPE was also shown to be highly correlated with that of standard inflation. These results suggest the feasibility of OPE as a potential clinical tool for evaluating corneal biomechanics in vivo.
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Kirby MA, Pelivanov I, Song S, Ambrozinski Ł, Yoon SJ, Gao L, Li D, Shen TT, Wang RK, O’Donnell M. Optical coherence elastography in ophthalmology. JOURNAL OF BIOMEDICAL OPTICS 2017; 22:1-28. [PMID: 29275544 PMCID: PMC5745712 DOI: 10.1117/1.jbo.22.12.121720] [Citation(s) in RCA: 120] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 12/14/2017] [Indexed: 05/03/2023]
Abstract
Optical coherence elastography (OCE) can provide clinically valuable information based on local measurements of tissue stiffness. Improved light sources and scanning methods in optical coherence tomography (OCT) have led to rapid growth in systems for high-resolution, quantitative elastography using imaged displacements and strains within soft tissue to infer local mechanical properties. We describe in some detail the physical processes underlying tissue mechanical response based on static and dynamic displacement methods. Namely, the assumptions commonly used to interpret displacement and strain measurements in terms of tissue elasticity for static OCE and propagating wave modes in dynamic OCE are discussed with the ultimate focus on OCT system design for ophthalmic applications. Practical OCT motion-tracking methods used to map tissue elasticity are also presented to fully describe technical developments in OCE, particularly noting those focused on the anterior segment of the eye. Clinical issues and future directions are discussed in the hope that OCE techniques will rapidly move forward to translational studies and clinical applications.
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Affiliation(s)
- Mitchell A. Kirby
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - Ivan Pelivanov
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - Shaozhen Song
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - Łukasz Ambrozinski
- Akademia Górniczo-Hutnicza University of Science and Technology, Krakow, Poland
| | - Soon Joon Yoon
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - Liang Gao
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
| | - David Li
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
- University of Washington, Department of Chemical Engineering, Seattle, Washington, United States
| | - Tueng T. Shen
- University of Washington, Department of Ophthalmology, Seattle, Washington, United States
| | - Ruikang K. Wang
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
- University of Washington, Department of Ophthalmology, Seattle, Washington, United States
| | - Matthew O’Donnell
- University of Washington, Department of Bioengineering, Seattle, Washington, United States
- Address all correspondence to: Matthew O’Donnell, E-mail:
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Weber IP, Yun SH, Scarcelli G, Franze K. The role of cell body density in ruminant retina mechanics assessed by atomic force and Brillouin microscopy. Phys Biol 2017; 14:065006. [PMID: 28406094 DOI: 10.1088/1478-3975/aa6d18] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Cells in the central nervous system (CNS) respond to the stiffness of their environment. CNS tissue is mechanically highly heterogeneous, thus providing motile cells with region-specific mechanical signals. While CNS mechanics has been measured with a variety of techniques, reported values of tissue stiffness vary greatly, and the morphological structures underlying spatial changes in tissue stiffness remain poorly understood. We here exploited two complementary techniques, contact-based atomic force microscopy and contact-free Brillouin microscopy, to determine the mechanical properties of ruminant retinae, which are built up by different tissue layers. As in all vertebrate retinae, layers of high cell body densities ('nuclear layers') alternate with layers of low cell body densities ('plexiform layers'). Different tissue layers varied significantly in their mechanical properties, with the photoreceptor layer being the stiffest region of the retina, and the inner plexiform layer belonging to the softest regions. As both techniques yielded similar results, our measurements allowed us to calibrate the Brillouin microscopy measurements and convert the Brillouin shift into a quantitative assessment of elastic tissue stiffness with optical resolution. Similar as in the mouse spinal cord and the developing Xenopus brain, we found a strong correlation between nuclear densities and tissue stiffness. Hence, the cellular composition of retinae appears to strongly contribute to local tissue stiffness, and Brillouin microscopy shows a great potential for the application in vivo to measure the mechanical properties of transparent tissues.
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Affiliation(s)
- Isabell P Weber
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
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Voorhees AP, Jan NJ, Austin ME, Flanagan JG, Sivak JM, Bilonick RA, Sigal IA. Lamina Cribrosa Pore Shape and Size as Predictors of Neural Tissue Mechanical Insult. Invest Ophthalmol Vis Sci 2017; 58:5336-5346. [PMID: 29049736 PMCID: PMC5649511 DOI: 10.1167/iovs.17-22015] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2017] [Accepted: 09/14/2017] [Indexed: 12/11/2022] Open
Abstract
Purpose The purpose of this study was to determine how the architecture of the lamina cribrosa (LC) microstructure, including the shape and size of the lamina pores, influences the IOP-induced deformation of the neural tissues within the LC pores using computational modeling. Methods We built seven specimen-specific finite element models of LC microstructure with distinct nonlinear anisotropic properties for LC beams and neural tissues based on histological sections from three sheep eyes. Changes in shape (aspect ratio and convexity) and size (area and perimeter length) due to IOP-induced hoop stress were calculated for 128 LC pores. Multivariate linear regression was used to determine if pore shape and size were correlated with the strain in the pores. We also compared the microstructure models to a homogenized model built following previous approaches. Results The LC microstructure resulted in focal tensile, compressive, and shear strains in the neural tissues of the LC that were not predicted by homogenized models. IOP-induced hoop stress caused pores to become larger and more convex; however, pore aspect ratio did not change consistently. Peak tensile strains within the pores were well predicted by a linear regression model considering the initial convexity (negative correlation, P < 0.001), aspect ratio (positive correlation, P < 0.01), and area (negative correlation, P < 0.01). Significant correlations were also found when considering the deformed shape and size of the LC pores. Conclusions The deformation of the LC neural tissues was largely dependent on the collagenous LC beams. Simple measures of LC pore shape and area provided good estimates of neural tissue biomechanical insult.
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Affiliation(s)
- Andrew P. Voorhees
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Ning-Jiun Jan
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Morgan E. Austin
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - John G. Flanagan
- Optometry and Vision Science, University of California Berkeley, Berkeley, California, United States
| | - Jeremy M. Sivak
- Ophthalmology and Vison Sciences, University of Toronto, Toronto, Ontario, Canada
| | - Richard A. Bilonick
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Ian A. Sigal
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
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Ambrósio, Jr R, Correia FF, Lopes B, Salomão MQ, Luz A, Dawson DG, Elsheikh A, Vinciguerra R, Vinciguerra P, Roberts CJ. Corneal Biomechanics in Ectatic Diseases: Refractive Surgery Implications. Open Ophthalmol J 2017; 11:176-193. [PMID: 28932334 PMCID: PMC5585467 DOI: 10.2174/1874364101711010176] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 05/16/2017] [Accepted: 06/15/2017] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Ectasia development occurs due to a chronic corneal biomechanical decompensation or weakness, resulting in stromal thinning and corneal protrusion. This leads to corneal steepening, increase in astigmatism, and irregularity. In corneal refractive surgery, the detection of mild forms of ectasia pre-operatively is essential to avoid post-operative progressive ectasia, which also depends on the impact of the procedure on the cornea. METHOD The advent of 3D tomography is proven as a significant advancement to further characterize corneal shape beyond front surface topography, which is still relevant. While screening tests for ectasia had been limited to corneal shape (geometry) assessment, clinical biomechanical assessment has been possible since the introduction of the Ocular Response Analyzer (Reichert Ophthalmic Instruments, Buffalo, USA) in 2005 and the Corvis ST (Oculus Optikgeräte GmbH, Wetzlar, Germany) in 2010. Direct clinical biomechanical evaluation is recognized as paramount, especially in detection of mild ectatic cases and characterization of the susceptibility for ectasia progression for any cornea. CONCLUSIONS The purpose of this review is to describe the current state of clinical evaluation of corneal biomechanics, focusing on the most recent advances of commercially available instruments and also on future developments, such as Brillouin microscopy.
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Affiliation(s)
- Renato Ambrósio, Jr
- Instituto de Olhos Renato Ambrósio, Rio de Janeiro, Brazil
- VisareRIO, Rio de Janeiro, Brazil
- Rio de Janeiro Corneal Tomography and Biomechanics Study Group, Rio de Janeiro, Brazil
- Brazilian Study Group of Artificial Intelligence and Corneal Analysis - BRAIN, Rio de Janeiro & Maceió, Brazil
- Department of Ophthalmology, Federal University of São Paulo, São Paulo, Brazil
| | - Fernando Faria Correia
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal
- ICVS/3B's-PT Government Associate Laboratory, Braga/Guimarães, Portugal
- Ophthalmology Department, Hospital de Braga, Braga, Portugal
| | - Bernardo Lopes
- Instituto de Olhos Renato Ambrósio, Rio de Janeiro, Brazil
- VisareRIO, Rio de Janeiro, Brazil
- Rio de Janeiro Corneal Tomography and Biomechanics Study Group, Rio de Janeiro, Brazil
- Brazilian Study Group of Artificial Intelligence and Corneal Analysis - BRAIN, Rio de Janeiro & Maceió, Brazil
- Department of Ophthalmology, Federal University of São Paulo, São Paulo, Brazil
| | - Marcella Q. Salomão
- Instituto de Olhos Renato Ambrósio, Rio de Janeiro, Brazil
- VisareRIO, Rio de Janeiro, Brazil
- Rio de Janeiro Corneal Tomography and Biomechanics Study Group, Rio de Janeiro, Brazil
- Brazilian Study Group of Artificial Intelligence and Corneal Analysis - BRAIN, Rio de Janeiro & Maceió, Brazil
- Department of Ophthalmology, Federal University of São Paulo, São Paulo, Brazil
| | - Allan Luz
- Rio de Janeiro Corneal Tomography and Biomechanics Study Group, Rio de Janeiro, Brazil
- Brazilian Study Group of Artificial Intelligence and Corneal Analysis - BRAIN, Rio de Janeiro & Maceió, Brazil
- Department of Ophthalmology, Federal University of São Paulo, São Paulo, Brazil
| | - Daniel G. Dawson
- The University of Florida Department of Ophthalmology, Gainesville, FL, USA
| | - Ahmed Elsheikh
- School of Engineering, University of Liverpool – Liverpool, United Kingdom
- NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, UK
| | - Riccardo Vinciguerra
- Department of Surgical Sciences, Division of Ophthalmology, University of Insubria, Varese, Italy
| | - Paolo Vinciguerra
- Department of Surgical Sciences, Division of Ophthalmology, University of Insubria, Varese, Italy
- Eye Center, Humanitas Clinical and Research Center, Via Manzoni 56, Rozzano (MI) – Italy
| | - Cynthia J. Roberts
- Department of Ophthalmology & Visual Science, Department of Biomedical Engineering, The Ohio State University – Columbus, OH, USA
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Intraocular Pressure, Axial Length, and Refractive Changes after Phacoemulsification and Trabeculectomy for Open-Angle Glaucoma. J Ophthalmol 2017; 2017:1203269. [PMID: 28660076 PMCID: PMC5474260 DOI: 10.1155/2017/1203269] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 04/30/2017] [Indexed: 11/17/2022] Open
Abstract
PURPOSE To compare changes in intraocular pressure (IOP), axial eye length (AEL), and refractive outcome in primary open-angle glaucoma patients undergoing cataract surgery and trabeculectomy in dependence of the sequence of surgeries. MATERIALS AND METHODS We retrospectively analysed 48 eyes. The changes in refraction, intraocular pressure, and axial eye length were analysed after surgery. In group A (21 subjects), phacoemulsification was performed before trabeculectomy, and in group B (27 subjects), trabeculectomy was performed before phacoemulsification with a minimum time span between interventions of 6 months. RESULTS The reduction in IOP and the decrease in AEL after trabeculectomy were significant after 6 and 12 months postsurgery (p < 0.001 each). The decrease in AEL was 0.42 ± 0.11% at 6 months after surgery and 0.40 ± 0.13% after 12 months from surgery; this decrease in AEL was comparable between the groups. The refractive outcome was significantly different between the groups (group A: 0.35 ± 0.75 dpt, group B: -0.05 ± 0.36 dpt, p = 0.018); in group A, trabeculectomy caused a hyperopic shift of 0.34 ± 0.44 dpt (p = 0.002) at 12 months postsurgery. CONCLUSION IOP reduction after trabeculectomy causes AEL shortening. The effect on refractive outcome depends on the sequence of surgeries. Better refractive outcome is achieved if phacoemulsification is performed after trabeculectomy.
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Coudrillier B, Campbell IC, Read AT, Geraldes DM, Vo NT, Feola A, Mulvihill J, Albon J, Abel RL, Ethier CR. Effects of Peripapillary Scleral Stiffening on the Deformation of the Lamina Cribrosa. Invest Ophthalmol Vis Sci 2017; 57:2666-77. [PMID: 27183053 PMCID: PMC4874475 DOI: 10.1167/iovs.15-18193] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Purpose Scleral stiffening has been proposed as a treatment for glaucoma to protect the lamina cribrosa (LC) from excessive intraocular pressure–induced deformation. Here we experimentally evaluated the effects of moderate stiffening of the peripapillary sclera on the deformation of the LC. Methods An annular sponge, saturated with 1.25% glutaraldehyde, was applied to the external surface of the peripapillary sclera for 5 minutes to stiffen the sclera. Tissue deformation was quantified in two groups of porcine eyes, using digital image correlation (DIC) or computed tomography imaging and digital volume correlation (DVC). In group A (n = 14), eyes were subjected to inflation testing before and after scleral stiffening. Digital image correlation was used to measure scleral deformation and quantify the magnitude of scleral stiffening. In group B (n = 5), the optic nerve head region was imaged using synchrotron radiation phase-contrast microcomputed tomography (PC μCT) at an isotropic spatial resolution of 3.2 μm. Digital volume correlation was used to compute the full-field three-dimensional deformation within the LC and evaluate the effects of peripapillary scleral cross-linking on LC biomechanics. Results On average, scleral treatment with glutaraldehyde caused a 34 ± 14% stiffening of the peripapillary sclera measured at 17 mm Hg and a 47 ± 12% decrease in the maximum tensile strain in the LC measured at 15 mm Hg. The reduction in LC strains was not due to cross-linking of the LC. Conclusions Peripapillary scleral stiffening is effective at reducing the magnitude of biomechanical strains within the LC. Its potential and future utilization in glaucoma axonal neuroprotection requires further investigation.
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Affiliation(s)
- Baptiste Coudrillier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, United States
| | - Ian C Campbell
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, United States 2Atlanta VA Medical Center, Decatur, Georgia, United States
| | - A Thomas Read
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, United States
| | - Diogo M Geraldes
- Biomechanics Group, Department of Mechanical Engineering, Imperial College London, London, United Kingdom
| | - Nghia T Vo
- Diamond Light Source, Didcot, United Kingdom
| | - Andrew Feola
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, United States
| | - John Mulvihill
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, United States
| | - Julie Albon
- Optic Nerve Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, Wales, United Kingdom 6Cardiff Institute of Tissue Engineering and Repair, Cardiff University, Cardiff, Wales, United Kingdom
| | - Richard L Abel
- Department of Surgery and Cancer, Imperial College, London, United Kingdom
| | - C Ross Ethier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, United States 2Atlanta VA Medical Center, Decatur, Georgia, United States
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48
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Randleman JB, Su JP, Scarcelli G. Biomechanical Changes After LASIK Flap Creation Combined With Rapid Cross-Linking Measured With Brillouin Microscopy. J Refract Surg 2017; 33:408-414. [DOI: 10.3928/1081597x-20170421-01] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 03/23/2017] [Indexed: 01/20/2023]
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Edrei E, Gather MC, Scarcelli G. Integration of spectral coronagraphy within VIPA-based spectrometers for high extinction Brillouin imaging. OPTICS EXPRESS 2017; 25:6895-6903. [PMID: 28381031 PMCID: PMC5772426 DOI: 10.1364/oe.25.006895] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
VIPA (virtually imaged phase array) spectrometers have enabled rapid Brillouin spectrum measurements and current designs of multi-stage VIPA spectrometers offer enough spectral extinction to probe transparent tissue, cells and biomaterials. However, in highly scattering media or in the presence of strong back-reflections, such as at interfaces between materials of different refractive indices, VIPA-based Brillouin spectral measurements are limited. While several approaches to address this issue have recently been pursued, important challenges remain. Here we have adapted the design of coronagraphs used for exosolar planet imaging to the spectral domain and integrated it in a double-stage VIPA spectrometer. We demonstrate that this yields an increase in extinction up to 20 dB, with nearly no added insertion loss. The power of this improvement is vividly demonstrated by Brillouin imaging close to reflecting interfaces without index matching or sample tilting.
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Affiliation(s)
- Eitan Edrei
- Fischell Department of Bioengineering, University of Maryland, College Park, Maryland 20742, USA
| | - Malte C. Gather
- SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, Scotland, UK
| | - Giuliano Scarcelli
- Fischell Department of Bioengineering, University of Maryland, College Park, Maryland 20742, USA
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Mari JM, Aung T, Cheng CY, Strouthidis NG, Girard MJA. A Digital Staining Algorithm for Optical Coherence Tomography Images of the Optic Nerve Head. Transl Vis Sci Technol 2017; 6:8. [PMID: 28174676 PMCID: PMC5291077 DOI: 10.1167/tvst.6.1.8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 09/13/2016] [Indexed: 01/26/2023] Open
Abstract
Purpose To digitally stain spectral-domain optical coherence tomography (OCT) images of the optic nerve head (ONH), and highlight either connective or neural tissues. Methods OCT volumes of the ONH were acquired from one eye of 10 healthy subjects. We processed all volumes with adaptive compensation to remove shadows and enhance deep tissue visibility. For each ONH, we identified the four most dissimilar pixel-intensity histograms, each of which was assumed to represent a tissue group. These four histograms formed a vector basis on which we ‘projected' each OCT volume in order to generate four digitally stained volumes P1 to P4. Digital staining was also verified using a digital phantom, and compared with k-means clustering for three and four clusters. Results Digital staining was able to isolate three regions of interest from the proposed phantom. For the ONH, the digitally stained images P1 highlighted mostly connective tissues, as demonstrated through an excellent contrast increase across the anterior lamina cribrosa boundary (3.6 ± 0.6 times). P2 highlighted the nerve fiber layer and the prelamina, P3 the remaining layers of the retina, and P4 the image background. Further, digital staining was able to separate ONH tissue layers that were not well separated by k-means clustering. Conclusion We have described an algorithm that can digitally stain connective and neural tissues in OCT images of the ONH. Translational Relevance Because connective and neural tissues are considerably altered in glaucoma, digital staining of the ONH tissues may be of interest in the clinical management of this pathology.
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Affiliation(s)
- Jean-Martial Mari
- GePaSud, Université de la Polynésie française, Tahiti, French Polynesia
| | - Tin Aung
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore ; Department of Ophthalmology, YLL School of Medicine, National University of Singapore, Singapore
| | - Ching-Yu Cheng
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore ; Department of Ophthalmology, YLL School of Medicine, National University of Singapore, Singapore ; Ophthalmology and Visual Sciences Academic Clinical Program (Eye ACP), Duke-NUS Medical School, Singapore
| | - Nicholas G Strouthidis
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore ; NIHR Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK ; Discipline of Clinical Ophthalmology and Eye Health, University of Sydney, Sydney, NSW, Australia
| | - Michaël J A Girard
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore ; Ophthalmic Engineering & Innovation Laboratory, Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, Singapore
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