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Villegas L, Zvietcovich F, Marcos S, Birkenfeld JS. Revealing regional variations in scleral shear modulus in a rabbit eye model using multi-directional ultrasound optical coherence elastography. Sci Rep 2024; 14:21010. [PMID: 39251655 PMCID: PMC11384758 DOI: 10.1038/s41598-024-71343-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2024] [Accepted: 08/27/2024] [Indexed: 09/11/2024] Open
Abstract
The mechanical properties of the sclera play a critical role in supporting the ocular structure and maintaining its shape. However, non-invasive measurements to quantify scleral biomechanics remain challenging. Recently introduced multi-directional optical coherence elastography (OCE) combined with an air-coupled ultrasound transducer for excitation of elastic surface waves was used to estimate phase speed and shear modulus in ex vivo rabbit globes (n = 7). The scleral phase speed (12.1 ± 3.2 m/s) was directional-dependent and higher than for corneal tissue (5.9 ± 1.4 m/s). In the tested locations, the sclera proved to be more anisotropic than the cornea by a factor of 11 in the maximum of modified planar anisotropy coefficient. The scleral shear moduli, estimated using a modified Rayleigh-Lamb wave model, showed significantly higher values in the circumferential direction (65.4 ± 31.9 kPa) than in meridional (22.5 ± 7.2 kPa); and in the anterior zone (27.3 ± 9.3 kPa) than in the posterior zone (17.8 ± 7.4 kPa). The multi-directional scanning approach allowed both quantification and radial mapping of estimated parameters within a single measurement. The results indicate that multi-directional OCE provides a valuable non-invasive assessment of scleral tissue properties that may be useful in the development of improved ocular models, the evaluation of potential myopia treatment strategies, and disease characterization and monitoring.
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Affiliation(s)
- Lupe Villegas
- Instituto de Óptica, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
| | - Fernando Zvietcovich
- Instituto de Óptica, Consejo Superior de Investigaciones Científicas, Madrid, Spain
- Department of Engineering, Pontificia Universidad Católica del Peru, Lima, Peru
| | - Susana Marcos
- Instituto de Óptica, Consejo Superior de Investigaciones Científicas, Madrid, Spain
- The Center for Visual Science, The Institute of Optics, Flaum Eye Institute, University of Rochester, Rochester, NY, USA
| | - Judith S Birkenfeld
- Instituto de Óptica, Consejo Superior de Investigaciones Científicas, Madrid, Spain
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2
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Wang P, Jiang J, Kong K, Fang X, Song Y, Lin F, Jiang J, Zeng J, Chen S, Zhang X. Construction of glaucoma model and comparing eyeball enlargement with myopia in Guinea pig. Exp Eye Res 2024; 246:110010. [PMID: 39069000 DOI: 10.1016/j.exer.2024.110010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Revised: 07/09/2024] [Accepted: 07/22/2024] [Indexed: 07/30/2024]
Abstract
This study aimed to develop and evaluate a guinea pig model for glaucoma, comparing resultant eyeball enlargement with an existing myopia model. Thirty guinea pigs underwent intracameral injection of magnetic microspheres to induce chronic ocular hypertension (COH). Intraocular pressure (IOP) was systematically monitored, revealing a successful induction of COH in 73.33% of the guinea pigs. The mean IOP increased from a baseline of 18.04 ± 1.33 mmHg, reaching a peak at week 3 (36.31 ± 6.13 mmHg) and remaining elevated for at least 7 weeks. All data are presented as mean ± standard deviation of the mean. Subsequently, detailed assessments were conducted to validate the established glaucoma model. Immunofluorescent staining demonstrated a significant decrease in the density of retinal ganglion cells (RGC) in the glaucoma group. Optic disc excavation and notable thinning of the lamina cribrosa (LC) were observed. The quantity of optic nerve ax·ons in glaucoma group gradually decreased from baseline (44553 ± 3608/mm2) to week 4 (28687 ± 2071/mm2) and week 8 (17977 ± 3697/mm2). Moreover, regarding the global enlargement of eyeballs, both the transverse and longitudinal axis in glaucomatous eyes were found to be significantly larger than that in myopic eyes, particularly in the anterior chamber depth (1.758 ± 0.113 mm vs. 1.151 ± 0.046 mm). These findings indicate distinct patterns of structural changes associated with glaucoma and myopia in the guinea pig model. This guinea pig model holds promise for future research aimed at exploring biomechanical mechanisms, therapeutic interventions, and advancing our understanding of the relationship between glaucoma and myopia.
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Affiliation(s)
- Peiyuan Wang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China
| | - Jiaxuan Jiang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China
| | - Kangjie Kong
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China
| | - Xiuli Fang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China
| | - Yunhe Song
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China
| | - Fengbin Lin
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China
| | - Jingwen Jiang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China
| | - Junwen Zeng
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China.
| | - Shida Chen
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China.
| | - Xiulan Zhang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou, China.
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Yue O, Wang X, Xie L, Bai Z, Zou X, Liu X. Biomimetic Exogenous "Tissue Batteries" as Artificial Power Sources for Implantable Bioelectronic Devices Manufacturing. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2307369. [PMID: 38196276 PMCID: PMC10953594 DOI: 10.1002/advs.202307369] [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: 10/04/2023] [Revised: 11/27/2023] [Indexed: 01/11/2024]
Abstract
Implantable bioelectronic devices (IBDs) have gained attention for their capacity to conformably detect physiological and pathological signals and further provide internal therapy. However, traditional power sources integrated into these IBDs possess intricate limitations such as bulkiness, rigidity, and biotoxicity. Recently, artificial "tissue batteries" (ATBs) have diffusely developed as artificial power sources for IBDs manufacturing, enabling comprehensive biological-activity monitoring, diagnosis, and therapy. ATBs are on-demand and designed to accommodate the soft and confining curved placement space of organisms, minimizing interface discrepancies, and providing ample power for clinical applications. This review presents the near-term advancements in ATBs, with a focus on their miniaturization, flexibility, biodegradability, and power density. Furthermore, it delves into material-screening, structural-design, and energy density across three distinct categories of TBs, distinguished by power supply strategies. These types encompass innovative energy storage devices (chemical batteries and supercapacitors), power conversion devices that harness power from human-body (biofuel cells, thermoelectric nanogenerators, bio-potential devices, piezoelectric harvesters, and triboelectric devices), and energy transfer devices that receive and utilize external energy (radiofrequency-ultrasound energy harvesters, ultrasound-induced energy harvesters, and photovoltaic devices). Ultimately, future challenges and prospects emphasize ATBs with the indispensability of bio-safety, flexibility, and high-volume energy density as crucial components in long-term implantable bioelectronic devices.
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Affiliation(s)
- Ouyang Yue
- College of Bioresources Chemical and Materials EngineeringShaanxi University of Science & TechnologyXi'anShaanxi710021China
- National Demonstration Center for Experimental Light Chemistry Engineering EducationShaanxi University of Science &TechnologyXi'anShaanxi710021China
| | - Xuechuan Wang
- College of Bioresources Chemical and Materials EngineeringShaanxi University of Science & TechnologyXi'anShaanxi710021China
- College of Chemistry and Chemical EngineeringShaanxi University of Science & TechnologyXi'anShaanxi710021China
| | - Long Xie
- College of Bioresources Chemical and Materials EngineeringShaanxi University of Science & TechnologyXi'anShaanxi710021China
- College of Chemistry and Chemical EngineeringShaanxi University of Science & TechnologyXi'anShaanxi710021China
| | - Zhongxue Bai
- College of Bioresources Chemical and Materials EngineeringShaanxi University of Science & TechnologyXi'anShaanxi710021China
- National Demonstration Center for Experimental Light Chemistry Engineering EducationShaanxi University of Science &TechnologyXi'anShaanxi710021China
| | - Xiaoliang Zou
- College of Bioresources Chemical and Materials EngineeringShaanxi University of Science & TechnologyXi'anShaanxi710021China
- National Demonstration Center for Experimental Light Chemistry Engineering EducationShaanxi University of Science &TechnologyXi'anShaanxi710021China
| | - Xinhua Liu
- College of Bioresources Chemical and Materials EngineeringShaanxi University of Science & TechnologyXi'anShaanxi710021China
- National Demonstration Center for Experimental Light Chemistry Engineering EducationShaanxi University of Science &TechnologyXi'anShaanxi710021China
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Niemczyk M, Iskander DR. Measuring intraocular pressure with OCT: the first approach. BIOMEDICAL OPTICS EXPRESS 2023; 14:4531-4541. [PMID: 37791274 PMCID: PMC10545197 DOI: 10.1364/boe.500546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Accepted: 07/18/2023] [Indexed: 10/05/2023]
Abstract
The variability of corneal OCT speckle statistics is indirectly related to changes in corneal microstructure, which may be induced by intraocular pressure (IOP). A new approach is considered, which attempts to estimate IOP based on corneal speckle statistics in OCT images. An area (A) under trajectories of contrast ratio with respect to stromal depth was calculated. The proposed method was evaluated on OCT images from the ex-vivo study on porcine eyeballs and in-vivo study on human corneas. A statistically significant multivariate linear regression model was obtained from the ex-vivo study: IOP = 0.70 · A - 6.11, in which IOP was precisely controlled in the anterior chamber. The ex-vivo study showed good correlation between A and IOP (R = 0.628, at the least) whereas the in-vivo study showed poor correlation between A and clinical air-puff tonometry based estimates of IOP (R = 0.351, at the most), indicating substantial differences between the two studies. The results of the ex-vivo study show the potential for OCT speckle statistics to be utilized for measuring IOP using static corneal imaging that does not require corneal deformation. Nevertheless, further work is needed to validate this approach in living human corneas.
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Affiliation(s)
- Marcela Niemczyk
- Department of Biomedical Engineering, Wroclaw University of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland
| | - D. Robert Iskander
- Department of Biomedical Engineering, Wroclaw University of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland
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5
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Yam GHF, Pi S, Du Y, Mehta JS. Posterior corneoscleral limbus: Architecture, stem cells, and clinical implications. Prog Retin Eye Res 2023; 96:101192. [PMID: 37392960 DOI: 10.1016/j.preteyeres.2023.101192] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 06/22/2023] [Accepted: 06/23/2023] [Indexed: 07/03/2023]
Abstract
The limbus is a transition from the cornea to conjunctiva and sclera. In human eyes, this thin strip has a rich variation of tissue structures and composition, typifying a change from scleral irregularity and opacity to corneal regularity and transparency; a variation from richly vascularized conjunctiva and sclera to avascular cornea; the neural passage and drainage of aqueous humor. The limbal stroma is enriched with circular fibres running parallel to the corneal circumference, giving its unique role in absorbing small pressure changes to maintain corneal curvature and refractivity. It contains specific niches housing different types of stem cells for the corneal epithelium, stromal keratocytes, corneal endothelium, and trabecular meshwork. This truly reflects the important roles of the limbus in ocular physiology, and the limbal functionality is crucial for corneal health and the entire visual system. Since the anterior limbus containing epithelial structures and limbal epithelial stem cells has been extensively reviewed, this article is focused on the posterior limbus. We have discussed the structural organization and cellular components of the region beneath the limbal epithelium, the characteristics of stem cell types: namely corneal stromal stem cells, endothelial progenitors and trabecular meshwork stem cells, and recent advances leading to the emergence of potential cell therapy options to replenish their respective mature cell types and to correct defects causing corneal abnormalities. We have reviewed different clinical disorders associated with defects of the posterior limbus and summarized the available preclinical and clinical evidence about the developing topic of cell-based therapy for corneal disorders.
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Affiliation(s)
- Gary Hin-Fai Yam
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA; Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore; McGowan Institute for Regenerative Medicine, Pittsburgh, PA, USA.
| | - Shaohua Pi
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Yiqin Du
- Department of Ophthalmology, University of South Florida, Tampa, FL, USA
| | - Jodhbir S Mehta
- Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore; Department of Cornea and External Eye Disease, Singapore National Eye Centre, Singapore; Ophthalmology and Visual Sciences Academic Clinical Program, Duke-National University of Singapore (NUS) Medical School, Singapore.
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Jonas JB, Jonas RA, Bikbov MM, Wang YX, Panda-Jonas S. Myopia: Histology, clinical features, and potential implications for the etiology of axial elongation. Prog Retin Eye Res 2023; 96:101156. [PMID: 36585290 DOI: 10.1016/j.preteyeres.2022.101156] [Citation(s) in RCA: 28] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Revised: 10/27/2022] [Accepted: 12/14/2022] [Indexed: 12/29/2022]
Abstract
Myopic axial elongation is associated with various non-pathological changes. These include a decrease in photoreceptor cell and retinal pigment epithelium (RPE) cell density and retinal layer thickness, mainly in the retro-equatorial to equatorial regions; choroidal and scleral thinning pronounced at the posterior pole and least marked at the ora serrata; and a shift in Bruch's membrane opening (BMO) occurring in moderately myopic eyes and typically in the temporal/inferior direction. The BMO shift leads to an overhang of Bruch's membrane (BM) into the nasal intrapapillary compartment and BM absence in the temporal region (i.e., parapapillary gamma zone), optic disc ovalization due to shortening of the ophthalmoscopically visible horizontal disc diameter, fovea-optic disc distance elongation, reduction in angle kappa, and straightening/stretching of the papillomacular retinal blood vessels and retinal nerve fibers. Highly myopic eyes additionally show an enlargement of all layers of the optic nerve canal, elongation and thinning of the lamina cribrosa, peripapillary scleral flange (i.e., parapapillary delta zone) and peripapillary choroidal border tissue, and development of circular parapapillary beta, gamma, and delta zone. Pathological features of high myopia include development of macular linear RPE defects (lacquer cracks), which widen to round RPE defects (patchy atrophies) with central BM defects, macular neovascularization, myopic macular retinoschisis, and glaucomatous/glaucoma-like and non-glaucomatous optic neuropathy. BM thickness is unrelated to axial length. Including the change in eye shape from a sphere in emmetropia to a prolate (rotational) ellipsoid in myopia, the features may be explained by a primary BM enlargement in the retro-equatorial/equatorial region leading to axial elongation.
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Affiliation(s)
- Jost B Jonas
- Department of Ophthalmology, Medical Faculty Mannheim of the Ruprecht-Karis-University, Mannheim, Germany; Institute for Clinical and Scientific Ophthalmology and Acupuncture Jonas & Panda, Heidelberg, Germany.
| | - Rahul A Jonas
- Department of Ophthalmology, University of Cologne, Cologne, Germany
| | | | - Ya Xing Wang
- Beijing Institute of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, China
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Kaplan MA, Bui BV, Ayton LN, Nguyen B, Grayden DB, John S. Establishing the Calibration Curve of a Compressive Ophthalmodynamometry Device. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2023; 2023:1-4. [PMID: 38082944 DOI: 10.1109/embc40787.2023.10340233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
The relationship between externally applied force and intraocular pressure was determined using an ex-vivo porcine eye model (N=9). Eyes were indented through the sclera with a convex ophthalmodynamometry head (ODM). Intraocular pressure and ophthalmodynamometric force were simultaneously recorded to establish a calibration curve of this indenter head. A calibration coefficient of 0.140 ± 0.009 mmHg/mN was established and was shown to be highly linear (r = 0.998 ± 0.002). Repeat application of ODM resulted in a 0.010 ± 0.002 mmHg/mN increase to the calibration coefficient.Clinical Relevance- ODM has been highlighted as a potential method of non-invasively estimating intracranial pressure. This study provides relevant data for the practical performance of ODM with similar compressive devices.
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Campigotto A, Campbell RJ, Lai Y. Correlation between corneal and contact lens deformation with changes in intraocular pressure for wearable monitoring systems. Eye (Lond) 2023; 37:2055-2060. [PMID: 36302975 PMCID: PMC10333185 DOI: 10.1038/s41433-022-02285-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 09/11/2022] [Accepted: 10/07/2022] [Indexed: 11/09/2022] Open
Abstract
OBJECTIVE The aim of this work is to evaluate the extent to which the eye's curvature deformation, due to changes in the intraocular pressure (IOP), can be directly tracked by an overlying contact lens. METHOD In this experimental study, using 12 cadaveric eyes, the IOP was increased from 10 to 36 mmHg, while video imaging was used to capture the three experimental variations. The deformation of the bare eye was used as a control, while the deformation of an overlying silicone grided contact lens and an overlying microfluidic IOP-sensing contact lens were examined and compared. RESULTS The relation between the slope of the radius of corneal curvature versus the IOP for both the bare eye and the marker contact lens yielded a linear relationship with a R2 value of 0.83. The microfluidic contact lens resulted in an average performance of 0.40 mm indicator movement/mmHg (SD 0.006). Comparing the slope of the marker contact lens deformation, to the performance of the microfluidic contact lens resulted in a R2 value of 0.78. The strain map of the overlaying grided contact lens showed most deformation occurring along the outer edge of the lens with increased deformation as increase IOP occurs; as well as with some negative, compressive movement near the central points. CONCLUSION The deformation from the curvature of the eye is significant enough from 10 to 36 mmHg that a silicone contact lens can capture and mimic those changes. The results show promise for optimization in contact lens-based IOP monitoring.
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Affiliation(s)
- Angelica Campigotto
- Department of Mechanical and Materials Engineering, Queen's University, Kingston, ON, Canada
| | - Robert J Campbell
- Department of Ophthalmology, Queen's University, Kingston, ON, Canada
- Department of Ophthalmology, Kingston Health Sciences Centre, Kingston, ON, Canada
| | - Yongjun Lai
- Department of Mechanical and Materials Engineering, Queen's University, Kingston, ON, Canada.
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Anatomic Peculiarities Associated with Axial Elongation of the Myopic Eye. J Clin Med 2023; 12:jcm12041317. [PMID: 36835853 PMCID: PMC9966891 DOI: 10.3390/jcm12041317] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 01/08/2023] [Accepted: 02/01/2023] [Indexed: 02/10/2023] Open
Abstract
PURPOSE To describe anatomical peculiarities associated with axial elongation in the human myopic eye. METHODS Reviewing the results of previous histomorphometrical investigations of enucleated human globes, as well as reviewing findings obtained in population-based studies and hospital-based clinical investigations of myopic patients and non-myopic individuals. RESULTS Myopic axial elongation is associated with a change from a mostly spherical eye shape to a prolate ellipsoid form. It is combined with choroidal and scleral thinning, most pronounced at the posterior pole and less pronounced in the fundus midperiphery. In the fundus midperiphery, the retina and density of the retinal pigment epithelium (RPE) and photoreceptors decrease with a longer axial length, while in the macular region, retinal thickness, RPE cell density, and choriocapillaris thickness are not related to axial length. With axial elongation, a parapapillary gamma zone develops, leading to an enlargement of the optic disc-fovea distance and a decrease in angle kappa. Axial elongation is also correlated with an increase in the surface and volume of Bruch's membrane (BM), while BM thickness remains unchanged. Axial elongation causes moderately myopic eyes to show a shift of BM opening to the foveal direction so that the horizontal disc diameter becomes shorter (with a consequent vertical ovalization of the optic disc shape), a temporal gamma zone develops, and the optic nerve exit takes an oblique course. Features of high myopia are an enlargement of the RPE opening (myopic parapapillary beta zone) and BM opening (secondary macrodisc), elongation and thinning of the lamina cribrosa, peripapillary scleral flange (parapapillary delta zone) and peripapillary choroidal border tissue, secondary BM defects in the macular region, myopic maculoschisis, macular neovascularization, and cobblestones in the fundus periphery. CONCLUSIONS These features combined may be explained by a growth in BM in the fundus midperiphery leading to axial elongation.
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McMonnies CW. Mechanisms of corneal trauma in response to rubbing and other intraocular pressure elevating activities in keratoconus. EXPERT REVIEW OF OPHTHALMOLOGY 2022. [DOI: 10.1080/17469899.2022.2153119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Charles W McMonnies
- Faculty of Medicine and Health, School of Optometry and Vision Science, University of New South Wales
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Lee DJ, Scruggs BA, Sánchez E, Thomas M, Faridi A. Transient Vision Loss Associated with Prefilled Aflibercept Syringes. OPHTHALMOLOGY SCIENCE 2022; 2. [PMID: 36211641 PMCID: PMC9541561 DOI: 10.1016/j.xops.2022.100115] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Purpose To describe cases of significant vision loss after intravitreal aflibercept administration using prefilled syringes (PFS) and to study the relationships among syringe design, injection speed, and injection force. Design Retrospective case series and experimental study. Participants Twelve patients who received intravitreal aflibercept via PFS. Methods All retina specialists (n = 13) at Oregon Health & Science University and the Veterans Affairs Portland Medical Center were queried in December 2020 to report episodes of significant vision loss after aflibercept PFS use. Chart review was completed for all affected patients. Using a commercially available force measuring system, injection force was measured for aflibercept PFS, ranibizumab PFS, and a tuberculin syringe at various injection speeds. Main Outcome Measures Number of significant vision loss episodes after aflibercept PFS use and average injection force (Newtons) at various injection speeds across different syringes. Results Ten specialists (76.9%) reported a perceived increase in vision loss after injection with aflibercept PFS. Sixteen events of light perception or worse vision were reported immediate after aflibercept PFS use. Chart review was available for 12 of these events. The indication for aflibercept was exudative age-related macular degeneration (n = 8), diabetic macular edema (n = 3), and central serous chorioretinopathy (n = 1). The median age of affected patients was 71 years (range, 49–94 years). Two patients were being treated for glaucoma (n = 1) or ocular hypertension (n = 1); 1 patient was a glaucoma suspect. Anterior chamber paracentesis was performed in 4 patients to normalize intraocular pressure (IOP) promptly. Laboratory experiments demonstrated that higher injection speeds were associated with higher injection forces for all syringe types. Injection forces were consistently greater with aflibercept PFS than with the ranibizumab PFS or tuberculin syringe (P < 0.0001). Conclusions Retina specialists at our institutions have noted numerous cases of severe transient vision loss with aflibercept PFS use. The average injection force may be greater with the aflibercept PFS when compared with other intravitreal anti–vascular endothelial growth factor (VEGF) options. Additional clinical studies are needed to understand better how syringe design and fluid dynamics may contribute to vision loss after injection.
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Affiliation(s)
- Daniel J. Lee
- Casey Eye Institute, Department of Ophthalmology, Oregon Health & Science University, Portland, Oregon
| | - Brittni A. Scruggs
- Casey Eye Institute, Department of Ophthalmology, Oregon Health & Science University, Portland, Oregon
| | - Erik Sánchez
- Department of Physics, Portland State University, Portland, Oregon
| | - Merina Thomas
- Casey Eye Institute, Department of Ophthalmology, Oregon Health & Science University, Portland, Oregon
| | - Ambar Faridi
- Casey Eye Institute, Department of Ophthalmology, Oregon Health & Science University, Portland, Oregon
- Department of Ophthalmology, Veteran Affairs Portland Health Care System, Portland, Oregon
- Correspondence: Ambar Faridi, MD, Casey Eye Institute, Oregon Health & Science University, 515 SW Campus Drive, Portland, OR 97239.
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12
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Mehr JA, Hatami-Marbini H. Experimental and numerical analysis of electroactive characteristics of scleral tissue. Acta Biomater 2022; 143:127-137. [PMID: 35038585 DOI: 10.1016/j.actbio.2022.01.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 01/04/2022] [Accepted: 01/10/2022] [Indexed: 11/15/2022]
Abstract
The sclera provides mechanical support to retina and protects internal contents of the eye against external injuries. The scleral extracellular matrix is mainly composed of collagen fibers and proteoglycans (PGs). At physiological pH, collagen molecules are neutral but PGs contain negatively charged glycosaminoglycan chains. Thus, the sclera can be considered as a polyelectrolyte hydrogel and is expected to exhibit mechanical response when subjected to electrical stimulations. In this study, we mounted scleral strips, dissected from the posterior part of porcine eyes, at the center of a custom-designed container between two electrodes. The container was filled with NaCl solution and the bending deformation of scleral strips as a function of the applied electric voltage was measured experimentally. It was found that scleral strips reached to an average bending angle of 3°, 10° and 23° when subjected to 5V, 10V, and 15V, respectively. We also created a chemo-electro-mechanical finite element model for simulating the experimental measurements by solving coupled Poisson-Nernst-Plank and equilibrium mechanical field equations. The scleral fixed charge density and modulus of elasticity were found by fitting the experimental data. The ion concentration distribution inside the domain was found numerically and was used to explain the underlying mechanisms for the scleral electroactive response. The numerical simulations were also used to investigate the effects of various parameters such as the electric voltage and fixed charge density on the scleral deformation under an electric field. STATEMENT OF SIGNIFICANCE: This manuscript investigates the electroactive response of scleral tissue. It demonstrates that the sclera deforms mechanically when subjected to electrical stimulations. A chemo-electro-mechanical model is also presented in order to numerically capture the electromechanical response of the sclera. This numerical model is used to explain the experimental observations by finding the ion distribution inside the tissue under an electric field. This work is significant because it shows that the sclera is an electroactive polyanionic hydrogel and it provides new information about the underlying mechanisms governing its mechanical and electrical properties.
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Affiliation(s)
- Jafar Arash Mehr
- Mechanical and Industrial Engineering Department, University of Illinois at Chicago, Chicago, IL USA
| | - Hamed Hatami-Marbini
- Mechanical and Industrial Engineering Department, University of Illinois at Chicago, Chicago, IL USA.
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13
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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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14
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Chan D, Won GJ, Read AT, Ethier CR, Thackaberry E, Crowell SR, Booler H, Bantseev V, Sivak JM. Application of an organotypic ocular perfusion model to assess intravitreal drug distribution in human and animal eyes. J R Soc Interface 2022; 19:20210734. [PMID: 35078337 PMCID: PMC8790337 DOI: 10.1098/rsif.2021.0734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Intravitreal (ITV) drug delivery is a new cornerstone for retinal therapeutics. Yet, predicting the disposition of formulations in the human eye remains a major translational hurdle. A prominent, but poorly understood, issue in pre-clinical ITV toxicity studies is unintended particle movements to the anterior chamber (AC). These particles can accumulate in the AC to dangerously raise intraocular pressure. Yet, anatomical differences, and the inability to obtain equivalent human data, make investigating this issue extremely challenging. We have developed an organotypic perfusion strategy to re-establish intraocular fluid flow, while maintaining homeostatic pressure and pH. Here, we used this approach with suitably sized microbeads to profile anterior and posterior ITV particle movements in live versus perfused porcine eyes, and in human donor eyes. Small-molecule suspensions were then tested with the system after exhibiting differing behaviours in vivo. Aggregate particle size is supported as an important determinant of particle movements in the human eye, and we note these data are consistent with a poroelastic model of bidirectional vitreous transport. Together, this approach uses ocular fluid dynamics to permit, to our knowledge, the first direct comparisons between particle behaviours from human ITV injections and animal models, with potential to speed pre-clinical development of retinal therapeutics.
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Affiliation(s)
- D. Chan
- Donald K Johnson Eye Institute, Krembil Research Institute, University Health Network, Toronto, Ontario, Canada
| | - G. J. Won
- Donald K Johnson Eye Institute, Krembil Research Institute, University Health Network, Toronto, Ontario, Canada
| | - A. T. Read
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University School of Medicine, Atlanta, Georgia, USA
| | - C. R. Ethier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University School of Medicine, Atlanta, Georgia, USA
| | - E. Thackaberry
- Safety Assessment, Genentech Inc., San Francisco, CA, USA
| | - S. R. Crowell
- Preclinical and Translational Pharmacokinetics and Pharmacodynamics (PTPK) Genentech Inc., San Francisco, CA, USA
| | - H. Booler
- Safety Assessment, Genentech Inc., San Francisco, CA, USA
| | - V. Bantseev
- Safety Assessment, Genentech Inc., San Francisco, CA, USA
| | - J. M. Sivak
- Donald K Johnson Eye Institute, Krembil Research Institute, University Health Network, Toronto, Ontario, Canada,Department of Ophthalmology and Vision Science, University of Toronto, Toronto, Ontario, Canada,Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
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15
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李 周, 杨 晓. [Mechanism of Bruch's Membrane in the Occurrence and Development of Myopia]. SICHUAN DA XUE XUE BAO. YI XUE BAN = JOURNAL OF SICHUAN UNIVERSITY. MEDICAL SCIENCE EDITION 2021; 52:913-916. [PMID: 34841753 PMCID: PMC10408825 DOI: 10.12182/20211160101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Indexed: 11/23/2022]
Abstract
Myopia is a process of ocular wall remodeling along with axial elongation after emmetropia decompensation, but the causal relationship among the changes taking place in ocular fundus structures during this process is not clear. The choroid, which lies between the retina and the sclera, plays an important role in the transmission of information related to myopia. The role of choroid in myopia is a hot research topic at present. Findings from animal experiments showed that form deprivation-induced changes in choroidal thickness may be related to the vascular perfusion, but the triggering mechanism of choroidal perfusion changes during the process of myopia still needs to to be further explored. Bruch's membrane is an elastic membrane located in the front of the choroid with good contractile properties. In the process of myopia, regional changes of the synthesis or biomechanics of Bruch's membrane may have formed the earliest structural basis of changes in choroidal thickness and blood flow. Taking choroidal thickness as a starting point, this paper focuses on the role and mechanism of Bruch's membrane in the occurrence and development of myopia, which may further deepen our understanding of the mechanism of changes in choroidal thickness, and provide a theoretical basis for the development of new therapeutic targets for myopia.
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Affiliation(s)
- 周越 李
- 眼科学国家重点实验室 中山大学中山眼科中心 (广州 510060)State Key Laboratory of Ophthalmology and Zhongshan Opthalmic Center, Sun Yat-Sen University, Guangzhou 510060, China
| | - 晓 杨
- 眼科学国家重点实验室 中山大学中山眼科中心 (广州 510060)State Key Laboratory of Ophthalmology and Zhongshan Opthalmic Center, Sun Yat-Sen University, Guangzhou 510060, China
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16
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Abstract
The corneal epithelium (CE) forms the outermost layer of the cornea. Despite its thickness of only 50 μm, the CE plays a key role as an initial barrier against any insults to the eye and contributes to the light refraction onto the retina required for clear vision. In the event of an injury, the cornea is equipped with many strategies contributing to competent wound healing, including angiogenic and immune privileges, and mechanotransduction. Various factors, including growth factors, keratin, cytokines, integrins, crystallins, basement membrane, and gap junction proteins are involved in CE wound healing and serve as markers in the healing process. Studies of CE wound healing are advancing rapidly in tandem with the rise of corneal bioengineering, which employs limbal epithelial stem cells as the primary source of cells utilizing various types of biomaterials as substrates.
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Affiliation(s)
- Norzana Abd Ghafar
- Pusat Perubatan Universiti Kebangsaan Malaysia, 56000Cheras, Kuala Lumpur, Malaysia
| | - Nahdia Afiifah Abdul Jalil
- Department of Anatomy, Faculty of Medicine, Universiti Kebangsaan Malaysia, 56000Cheras, Kuala Lumpur, Malaysia
| | - Taty Anna Kamarudin
- Department of Anatomy, Faculty of Medicine, Universiti Kebangsaan Malaysia, 56000Cheras, Kuala Lumpur, Malaysia
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17
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Józwik A, Asejczyk-Widlicka M, Kurzynowski P, Pierscionek BK. How a dynamic optical system maintains image quality: Self-adjustment of the human eye. J Vis 2021; 21:6. [PMID: 33656560 PMCID: PMC7938001 DOI: 10.1167/jov.21.3.6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The eyeball is continually subjected to forces that cause alterations to its shape and dimensions, as well as to its optical components. Forces that induce accommodation result in an intentional change in focus; others, such as the effect of intraocular pressure fluctuations, are more subtle. Although the mechanical properties of the eyeball and its components permit mediation of such subtle forces, the concomitant optical changes are not detected by the visual system. Optical self-adjustment is postulated as the mechanism that maintains image quality. The purpose of this study was to investigate how self-adjustment occurs by using an optical model of the eyeball and to test the requisite optical and biometric conditions.
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Affiliation(s)
- Agnieszka Józwik
- Department of Optics and Photonics, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland.,
| | - Magdalena Asejczyk-Widlicka
- Department of Optics and Photonics, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland.,
| | - Piotr Kurzynowski
- Department of Optics and Photonics, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland.,
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Silverman RH, Urs R, Tezel G, Yang X, Nelson I, Ketterling JA. Retrobulbar blood flow in rat eyes during acute elevation of intraocular pressure. Exp Eye Res 2021; 207:108606. [PMID: 33930396 DOI: 10.1016/j.exer.2021.108606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 04/12/2021] [Accepted: 04/22/2021] [Indexed: 10/21/2022]
Abstract
Most studies of the effect of acute elevation of intraocular pressure (IOP) on ocular blood-flow have utilized optical coherence tomography (OCT) to characterize retinal and choroidal flow and vascular density. This study investigates the effect of acute IOP elevation on blood flow velocity in the retrobulbar arteries and veins supplying and draining the eye, which, unlike the retinal and choroidal vasculature, are not directly compressed as IOP is increased. By cannulation of the anterior chamber of 20 Sprague-Dawley rats, we increased IOP in 10 mmHg steps from 10 to 60 mmHg and returned to 10 mmHg. After 1 min at each IOP (and 3 min after return to 10 mmHg), we acquired 18 MHz plane-wave ultrasound data at 3000 compound images/sec for 1.5 s. We produced color-flow Doppler images by digital signal processing of the ultrasound data, identified retrobulbar arteries and veins, generated spectrograms depicting flow velocity over the cardiac cycle and characterized changes of vascular density and perfusion in the orbit overall. Systolic, diastolic and mean velocities and resistive and pulsatile indices were determined from arterial spectrograms at each IOP level. Baseline mean arterial and mean venous velocities averaged 30.9 ± 10.8 and 8.5 ± 3.3 mm/s, respectively. Arterial velocity progressively decreased and resistance indices increased at and above an IOP of 30 mmHg. Mean arterial velocity at 60 mmHg dropped by 55% with respect to baseline, while venous velocity decreased by 20%. Arterial and venous velocities and resistance returned to near baseline after IOP was restored to 10 mmHg. Both vascular density and orbital perfusion decreased with IOP, but while perfusion returned to near normal when IOP returned to 10 mmHg, density remained reduced. Our findings are consistent with OCT-based studies showing reduced perfusion of the retina at levels comparable to retrobulbar arterial flow velocity change with increased IOP. The lesser effect on venous flow is possibly attributable to partial collapse of the venous lumen as volumetric venous outflow decreased at high IOP. The continued reduction in orbital vascular density 3 min after restoration of IOP to 10 mmHg might be attributable to persisting narrowing of capillaries, but this needs to be verified in future studies.
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Affiliation(s)
- Ronald H Silverman
- Department of Ophthalmology, Columbia University Irving Medical Center, New York, NY, USA.
| | - Raksha Urs
- Department of Ophthalmology, Columbia University Irving Medical Center, New York, NY, USA
| | - Gulgun Tezel
- Department of Ophthalmology, Columbia University Irving Medical Center, New York, NY, USA
| | - Xiangjun Yang
- Department of Ophthalmology, Columbia University Irving Medical Center, New York, NY, USA
| | - Inez Nelson
- Department of Ophthalmology, Columbia University Irving Medical Center, New York, NY, USA
| | - Jeffrey A Ketterling
- F.L. Lizzi Center for Biomedical Engineering, Riverside Research, New York, NY, USA
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Niemczyk M, Danielewska ME, Kostyszak MA, Lewandowski D, Iskander DR. The effect of intraocular pressure elevation and related ocular biometry changes on corneal OCT speckle distribution in porcine eyes. PLoS One 2021; 16:e0249213. [PMID: 33770135 PMCID: PMC7997020 DOI: 10.1371/journal.pone.0249213] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 03/14/2021] [Indexed: 11/21/2022] Open
Abstract
The aim of this study was to evaluate the influence of increase in intraocular pressure (IOP) and cooccurring changes in ocular biometry parameters on the corneal optical coherence tomography (OCT) speckle distribution in ex-vivo experiments on porcine intact eyes. Twenty-three eyeballs were used in the inflation test where IOP in the anterior chamber was precisely set from 10 mmHg to 40 mmHg in steps of 5 mmHg and where eye biometry was utilized (IOL Master 700). To assess the influence of the duration of the experiment on the OCT speckle statistics, the second experiment was performed with 10 eyeballs at the constant IOP of 15 mmHg. Based on the OCT scans of central cornea (Copernicus REVO), spatial maps of the scale parameter (a) and the shape parameter (v) of the gamma distribution speckle model were estimated. The means of both parameters for each spatial map were computed within the 2 mm of the central stroma. Both distributional parameters statistically significantly varied with IOP and time (one way repeated measures ANOVA, all p-values < 0.001). The a parameter revealed a faster statistically significant increase in IOP up to 25 mmHg, regardless of time. Central corneal thickness (CCT), the anterior chamber depth, and the mean equivalent spherical power varied significantly with IOP, whereas CCT and axial length changed statistically significantly with time. Statistically significant correlation was found between CCT and the a parameter, after removing IOP as a confounding factor (r = -0.576, p < 0.001). The parameters of the gamma distribution can be used not only for identifying IOP induced changes in the optical scattering within the corneal stroma, but also in corneal geometry. The approach of corneal speckle analysis could be potentially utilized for an indirect and noninvasive assessment of some properties of corneal stroma.
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Affiliation(s)
- Marcela Niemczyk
- Department of Biomedical Engineering, Wroclaw University of Science and Technology, Wroclaw, Poland
| | - Monika E. Danielewska
- Department of Biomedical Engineering, Wroclaw University of Science and Technology, Wroclaw, Poland
| | - Malgorzata A. Kostyszak
- Department of Biomedical Engineering, Wroclaw University of Science and Technology, Wroclaw, Poland
| | - Daniel Lewandowski
- Department of Mechanics, Materials and Biomedical Engineering, Wroclaw University of Science and Technology, Wroclaw, Poland
| | - D. Robert Iskander
- Department of Biomedical Engineering, Wroclaw University of Science and Technology, Wroclaw, Poland
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20
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Effect of variations of corneal physiology on novel non-invasive intraocular pressure monitoring soft contact lens. Biomed Microdevices 2021; 23:16. [PMID: 33725182 DOI: 10.1007/s10544-021-00555-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/22/2021] [Indexed: 10/21/2022]
Abstract
Glaucoma is the leading cause of irreversible blindness around the world. With its slow asymptomatic progression, there is an emphasis on early detection and frequent monitoring. A novel microfluidic contact lens has been established as a potential way to track the fluctuations of the intraocular pressure (IOP) which is a key indicator for diagnosing and monitoring glaucoma progression. The purpose of this article is to determine the effect of physiological variations of the eye on the performance of the microfluidic contact lens. Ultrasound biomicroscopy (UBM) was used to measure the central corneal thickness (CCT) and radius of corneal curvature (RCC) for a series of 16 fresh enucleated porcine eyes. The effect of these corneal anatomic features on device performance was then assessed by systematically adjusting intraocular pressure from 10 to 34 mmHg and monitoring the device indicator response. The performance of the microfluidic contact lens was determined by finding the amount the indicator fluid shifted in position as a result of 1 mmHg IOP increase. The relationship between IOP and indicator fluid was found to be linear for all eyes. The slope of the indicator fluid movement as a result of the IOP was evaluated against the CCT and RCC of each porcine eye. This yielded low correlation coefficients, 0.057 for CCT and 0.024 for RCC, meaning that these physiological differences showed no systematic impact on the measurements made with the contact lens.
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21
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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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22
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Shinkai Y, Yoneda K, Sotozono C. Ex Vivo Comparison of Intraocular Pressure Fluctuation During Pars Plana Vitrectomy Performed Using 25- and 27-Gauge Systems. Ophthalmic Res 2020; 65:210-215. [PMID: 33011731 DOI: 10.1159/000511948] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 09/17/2020] [Indexed: 11/19/2022]
Abstract
INTRODUCTION The purpose of this study was to compare intraoperative intraocular pressure fluctuation using different aspiration systems and 25- and 27-gauge vitreous surgery probes. METHODS Ex vivo, pars plana, 25- and 27-gauge vitreous surgery was performed on four porcine eyes, and IOP fluctuations were evaluated. We performed three-port vitrectomy using the Constellation® Vision or the EVA® Phaco-Vitrectomy system. Each 20-s experiment was conducted five times for each set of conditions, each with the same substituted balanced salt solution. Real-time intraoperative intraocular pressure measurement was performed at the distal end of the infusion tube. Intraocular pressure was measured during core vitrectomy; core vitrectomy with fluid aspiration; peripheral vitreous shaving with scleral indentation; and fluid-gas exchange. The Mann-Whitney U test was used to evaluate statistical significance. RESULTS Mean ± standard deviation intraoperative intraocular pressure fluctuation during 25- and 27-gauge core vitrectomy were 15.9 ± 1.6 mmHg and 11.9 ± 1.4 mmHg, respectively (P < 0.05), using the Constellation system; 23.2 ± 1.4 mmHg and 14.1 ± 0.7 mm Hg, respectively (P < 0.001), using the EVA vacuum mode; and 15.0 ± 0.5 mmHg and 11.5 ± 1.4 mmHg, respectively (P < 0.05), using the EVA flow mode. The smallest intraoperative intraocular pressure fluctuations during core vitrectomy with fluid aspiration, peripheral vitreous shaving with scleral indentation, and fluid-gas exchange, were all achieved using the 27-gauge EVA flow mode; these values were 14.2 ± 0.4 mmHg, 35.7 ± 0.9 mmHg, and 6.4 ± 0.2 mmHg, respectively. CONCLUSION Regardless of the aspiration system, intraoperative intraocular pressure fluctuation was lower during 27-gauge than during 25-gauge vitrectomy. The 27-gauge EVA flow mode produced optimal intraoperative intraocular pressure stability.
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Affiliation(s)
- Yoichiro Shinkai
- Department of Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Kazuhito Yoneda
- Department of Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Chie Sotozono
- Department of Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan
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Wilson A, Jones J, Tyrer JR, Marshall J. An interferometric ex vivo study of corneal biomechanics under physiologically representative loading, highlighting the role of the limbus in pressure compensation. EYE AND VISION 2020; 7:43. [PMID: 32832574 PMCID: PMC7433364 DOI: 10.1186/s40662-020-00207-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Accepted: 07/25/2020] [Indexed: 12/23/2022]
Abstract
Background The mechanical properties of the cornea are complex and regionally variable. This paper uses an original method to investigate the biomechanics of the cornea in response to hydrostatic loading over the typical physiological range of intra-ocular pressure (IOP) fluctuations thereby increasing understanding of clinically relevant corneal biomechanical properties and their contributions to the refractive properties of the cornea. Methods Displacement speckle pattern interferometry (DSPI) was used to measure the total surface displacement of 40 porcine and 6 human corneal-scleral specimens in response to pressure variations up to 1 mmHg from a baseline of 16.5 mmHg. All specimens were mounted in a modified artificial anterior chamber (AAC) and loaded hydrostatically. Areas of high strain in response to loading were identified by comparing the displacements across different regions. Results The nature of the response of the corneal surface to loading demonstrated high regional topographic variation. Mechanical properties were shown to be asymmetrical, and deformation of the limbal and pre-limbal regions dominated these responses respectively with over 90% (N-T) and 60% (S-I) of the total maximum displacement occurring in these regions indicating high-strain. In contrast, the curvature of the central cornea remained relatively unchanged merely translating in position. Conclusions The limbal and pre-limbal regions of the cornea appear to be fundamental to the absorption of small pressure fluctuations facilitating the curvature of the central cornea to remain relatively unchanged. The differential mechanical properties of this region could have important implications for the application of corneal surgery and corneal crosslinking, warranting further investigation.
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Affiliation(s)
- Abby Wilson
- Wolfson School of Mechanical, Manufacturing and Electrical Engineering, Loughborough University, Loughborough, UK
| | - John Jones
- Laser Optical Engineering Ltd., Derbyshire, UK
| | - John R Tyrer
- Wolfson School of Mechanical, Manufacturing and Electrical Engineering, Loughborough University, Loughborough, UK.,Laser Optical Engineering Ltd., Derbyshire, UK
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24
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Campigotto A, Lai Y. A novel non‐invasive wearable sensor for intraocular pressure measurement. ACTA ACUST UNITED AC 2020. [DOI: 10.1002/mds3.10086] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Angelica Campigotto
- Department of Mechanical Engineering Queen’s University Kingston Ontario Canada
| | - Yongjun Lai
- Department of Mechanical Engineering Queen’s University Kingston Ontario Canada
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25
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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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Xie Y, Ouyang X, Wang G. Mechanical strain affects collagen metabolism-related gene expression in scleral fibroblasts. Biomed Pharmacother 2020; 126:110095. [PMID: 32217440 DOI: 10.1016/j.biopha.2020.110095] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 03/06/2020] [Accepted: 03/09/2020] [Indexed: 12/28/2022] Open
Abstract
We previously demonstrated that collagen metabolism affects scleral mechanical properties and scleral remodeling. Scleral remodeling changes the mechanical strain on sclera and scleral fibroblasts. We postulated that mechanical strain changes affect collagen metabolism in scleral fibroblasts. To understand the differences in collagen metabolism in scleral fibroblasts related to mechanical strain changes, scleral fibroblasts were isolated and cultured under different mechanical strains using the FX-4000 system or were treated with the TGF-β1 and TGFBR1 inhibitor LY364947. The collagen metabolism-related gene expression levels were detected. The results showed that the appropriate (lower) mechanical strain improved collagen synthesis and reduced collagen decomposition. In contrast, higher mechanical strain reduced collagen synthesis and enhanced collagen decomposition, especially a sustained higher strain. Furthermore, the effect of a transitory higher strain was recoverable, and collagen metabolism in scleral fibroblasts was regulated by TGF-β1. These results suggested that mechanical strain mediates TGF-β1 expression to regulate collagen metabolism in scleral fibroblasts, thereby affect scleral tissue remodeling.
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Affiliation(s)
- Yongfang Xie
- Key Laboratory of Biological Medicines in Universities of Shandong Province, Weifang Medical University, Weifang, 261053, China
| | - Xinli Ouyang
- Key Laboratory of Biological Medicines in Universities of Shandong Province, Weifang Medical University, Weifang, 261053, China
| | - Guohui Wang
- Key Laboratory of Biological Medicines in Universities of Shandong Province, Weifang Medical University, Weifang, 261053, China.
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Nasrollahi A, Rizzo P. Modeling a new dynamic approach to measure intraocular pressure with solitary waves. J Mech Behav Biomed Mater 2020; 103:103534. [DOI: 10.1016/j.jmbbm.2019.103534] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 10/21/2019] [Accepted: 11/12/2019] [Indexed: 10/25/2022]
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Araci IE, Agaoglu S, Lee JY, Rivas Yepes L, Diep P, Martini M, Schmidt A. Flow stabilization in wearable microfluidic sensors enables noise suppression. LAB ON A CHIP 2019; 19:3899-3908. [PMID: 31641709 DOI: 10.1039/c9lc00842j] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Dilatometric strain sensors (DSS) that work based on detection of volume change in microfluidic channels; i) are highly sensitive to biaxial strain, ii) can be fabricated using only soft and transparent materials, and iii) are easy to integrate with smart-phones. These features are especially attractive for contact lens based intraocular pressure (IOP) sensing applications. The inherent flow stabilization of the microfluidic systems is an additional advantage suitable for filtering out rapid fluctuations. Here, we have demonstrated that the low-pass filtering in microfluidic sensors improves the signal-to-noise-ratio for ophthalmic applications. We have fabricated devices with a time constant in the range of 1-200 seconds. We have demonstrated that the device architecture and working liquid viscosity (10-866 cSt) are the two independent factors that determine the sensor time constant. We have developed an equivalent circuit model for the DSS that accurately represents the experimental results thus can be used as a computational model for design and development of microfluidic sensors. For a sensor with the time constant of 4 s, we report that microfluidic signal filtering in IOP monitoring applications can suppress the rapid fluctuations (i.e., the noise due to ocular pulsation, blinking etc.) by 9 dB without the need for electronic components.
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Affiliation(s)
- I Emre Araci
- Department of Bioengineering, Santa Clara University, Santa Clara, CA, USA.
| | - Sevda Agaoglu
- Department of Bioengineering, Santa Clara University, Santa Clara, CA, USA.
| | - Ju Young Lee
- Department of Bioengineering, Santa Clara University, Santa Clara, CA, USA.
| | - Laura Rivas Yepes
- Department of Bioengineering, Santa Clara University, Santa Clara, CA, USA.
| | - Priscilla Diep
- Department of Bioengineering, Santa Clara University, Santa Clara, CA, USA.
| | - Matthew Martini
- Department of Bioengineering, Santa Clara University, Santa Clara, CA, USA.
| | - Andrew Schmidt
- Department of Bioengineering, Santa Clara University, Santa Clara, CA, USA.
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Kazaili A, Lawman S, Geraghty B, Eliasy A, Zheng Y, Shen Y, Akhtar R. Line-Field Optical Coherence Tomography as a tool for In vitro characterization of corneal biomechanics under physiological pressures. Sci Rep 2019; 9:6321. [PMID: 31004101 PMCID: PMC6474860 DOI: 10.1038/s41598-019-42789-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Accepted: 04/03/2019] [Indexed: 12/02/2022] Open
Abstract
There has been a lot of interest in accurately characterising corneal biomechanical properties under intraocular pressure (IOP) to help better understand ocular pathologies that are associated with elevated IOP. This study investigates the novel use of Line-Field Optical Coherence Tomography (LF-OCT) as an elastographic tool for accurately measuring mechanical properties of porcine corneas based on volumetric deformation following varying IOPs. A custom-built LF-OCT was used to measure geometrical and corneal surface displacement changes in porcine corneas under a range of IOPs, from 0-60 mmHg. Corneal thickness, elastic properties and hysteresis were calculated as a function of pressure. In addition, the effects of hydration were explored. We found that the elastic modulus increased in a linear fashion with IOP. Corneal thickness was found to reduce with IOP, decreasing 14% from 0 to 60 mmHg. Prolonged hydration in phosphate buffered saline (PBS) was found to significantly increase the elastic modulus and corneal hysteresis. Our study demonstrates that LF-OCT can be used to accurately measure the elastic properties based on volumetric deformation following physiological pressures. Furthermore, we show that prolonged hydration in PBS has a significant effect on the measured corneal properties.
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Affiliation(s)
- Ahmed Kazaili
- Department of Mechanical, Materials and Aerospace Engineering, School of Engineering, University of Liverpool, Liverpool, L69 3GH, UK
- Department of Biomedical Engineering, College of Engineering, University of Babylon, Hillah, Iraq
| | - Samuel Lawman
- Department of Electrical Engineering and Electronics, University of Liverpool, Liverpool, L69 3GJ, UK
- Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, L7 8TX, UK
| | - Brendan Geraghty
- Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, L7 8TX, UK
| | - Ashkan Eliasy
- Department of Mechanical, Materials and Aerospace Engineering, School of Engineering, University of Liverpool, Liverpool, L69 3GH, UK
| | - Yalin Zheng
- Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, L7 8TX, UK
| | - Yaochun Shen
- Department of Electrical Engineering and Electronics, University of Liverpool, Liverpool, L69 3GJ, UK
| | - Riaz Akhtar
- Department of Mechanical, Materials and Aerospace Engineering, School of Engineering, University of Liverpool, Liverpool, L69 3GH, UK.
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Wang X, Teoh CKG, Chan ASY, Thangarajoo S, Jonas JB, Girard MJA. Biomechanical Properties of Bruch's Membrane-Choroid Complex and Their Influence on Optic Nerve Head Biomechanics. Invest Ophthalmol Vis Sci 2019; 59:2808-2817. [PMID: 30029276 DOI: 10.1167/iovs.17-22069] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose The purpose of this study was to measure the rupture pressure and the biomechanical properties of porcine Bruch's membrane (BM)-choroid complex (BMCC) and the influences of BM on optic nerve head (ONH) tissues. Methods The biomechanical properties of BMCC were extracted through uniaxial tensile tests of 10 BMCC specimens from 10 porcine eyes; the rupture pressures of BMCC were measured through burst tests of 20 porcine eyes; and the influence of BM on IOP-induced ONH deformations were investigated using finite element (FE) analysis. Results Uniaxial experimental results showed that the average elastic (tangent) moduli of BMCC samples at 0% and 5% strain were 1.60 ± 0.81 and 2.44 ± 1.02 MPa, respectively. Burst tests showed that, on average, BMCC could sustain an IOP of 82 mm Hg before rupture. FE simulation results predicted that, under elevated IOP, prelamina tissue strains increased with increasing BM stiffness. On the contrary, lamina cribrosa strains showed an opposite trend but the effects were small. Conclusions BMCC stiffness is comparable or higher than those of other ocular tissues and can sustain a relatively high pressure before rupture. Additionally, BM may have a nonnegligible influence on IOP-induced ONH deformations.
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Affiliation(s)
- Xiaofei Wang
- Ophthalmic Engineering & Innovation Laboratory, Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, Singapore
| | - Clarence Ken Guan Teoh
- Ophthalmic Engineering & Innovation Laboratory, Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, Singapore
| | - Anita S Y Chan
- Translational Ophthalmic Pathology, Singapore Eye Research Institute, Ophthalmic Pathology Service, Singapore National Eye Centre, Singapore.,Duke-National University of Singapore Medical School, Singapore
| | - Sathiyan Thangarajoo
- Ophthalmic Engineering & Innovation Laboratory, Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, Singapore
| | - Jost B Jonas
- Department of Ophthalmology, Medical Faculty Mannheim of the Ruprecht-Karls-University, Heidelberg, Germany.,Beijing Institute of Ophthalmology, Beijing Tongren Eye Centre, Beijing Tongren Hospital, Capital Medical University, and Beijing Key Laboratory of Ophthalmology and Visual Sciences, Beijing, China
| | - Michaël J A Girard
- Ophthalmic Engineering & Innovation Laboratory, Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, Singapore.,Translational Ophthalmic Pathology, Singapore Eye Research Institute, Ophthalmic Pathology Service, Singapore National Eye Centre, Singapore
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Rashidi N, Thomas VS, Amini R. Theoretical Assessment of the Risk of Ocular Hypotony in Patients With Intravitreal Gas Bubbles Who Travel Through Subsea Tunnels. Transl Vis Sci Technol 2019; 8:4. [PMID: 30627479 PMCID: PMC6322713 DOI: 10.1167/tvst.8.1.4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 10/12/2018] [Indexed: 01/16/2023] Open
Abstract
Purpose This study was conducted to investigate changes in intraocular pressure (IOP) in the presence of intravitreal gas bubbles in individuals who travel through subsea tunnels. Methods Using a mathematical model, we simulated alterations in ocular globe shape, aqueous humor flow, volume of intravitreal gas bubbles, and IOP due to elevation changes during travel through subsea tunnels. We simulated five tunnels with different features as case studies. The role of key modeling parameters was further evaluated in a parametric study. Results In three out of the five simulated tunnels (i.e., Seikan Tunnel, Bomlafjord Tunnel, and the Atlantic Ocean Tunnel), the patients were potentially at risk at lower portions of the tunnels since the IOP dropped to values less than 5 mm Hg, the clinical threshold for ocular hypotony. During ascent, the IOP increased to the normal value of 15 mm Hg and in some cases to higher values (e.g., a peak value of 22 mm Hg in Seikan Tunnel). Conclusions Our model predicted that in the presence of intravitreal gas bubbles, the IOP could drop to extremely low values when patients descend to lower elevations in some tunnels. Such low IOP values could cause bleeding and/or retinal detachment. Since many factors (e.g., tunnel specifications and/or patient-specific characteristics) could affect the IOP during subsea travel, caution (beyond avoiding airplane flights) should be taken in advising patients about travel restrictions following intravitreal gas injections. Translational Relevance Our findings highlight the potential risk for hypotony in the presence of intravitreal gas bubbles during subsea travels.
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Affiliation(s)
- Neda Rashidi
- Department of Biomedical Engineering, The University of Akron, Akron, OH, USA
| | - Vineet S Thomas
- Department of Biomedical Engineering, The University of Akron, Akron, OH, USA
| | - Rouzbeh Amini
- Department of Biomedical Engineering, The University of Akron, Akron, OH, USA
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Masterton S, Ahearne M. Mechanobiology of the corneal epithelium. Exp Eye Res 2018; 177:122-129. [PMID: 30086260 PMCID: PMC6280025 DOI: 10.1016/j.exer.2018.08.001] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 07/16/2018] [Accepted: 08/03/2018] [Indexed: 12/16/2022]
Abstract
There has been a drive to develop new cell based therapies to treat corneal blindness, one of the most common causes of blindness worldwide. Mechanical and physical cues are known to regulate the behavior of many cell types, however studies examining these effects on corneal epithelial cells have been limited in number and their findings have not previously been amalgamated and contrasted. Here, we provide an overview of the different types of mechanical stimuli to which the corneal epithelium is exposed and the influence that these have on the cells. Shear stress from the tear film motion and blinking, extracellular matrix stiffness and external physical forces such as eye rubbing and contact lens wear are among some of the forms of mechanical stimuli that the epithelium experiences. In vivo and in vitro studies examining the mechanobiology on corneal epithelial cells under differing mechanical environments are explored. A greater understanding of the mechanobiology of the corneal epithelium has the potential to lead to improved tissue engineering and cell based therapies to repair and regenerate damaged cornea.
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Affiliation(s)
- Sophia Masterton
- Dept of Mechanical and Manufacturing Engineering, School of Engineering, Trinity College Dublin, University of Dublin, Ireland; Trinity Centre for Bioengineering, Trinity Biomedical Science Institute, Trinity College Dublin, University of Dublin, Ireland
| | - Mark Ahearne
- Dept of Mechanical and Manufacturing Engineering, School of Engineering, Trinity College Dublin, University of Dublin, Ireland; Trinity Centre for Bioengineering, Trinity Biomedical Science Institute, Trinity College Dublin, University of Dublin, Ireland.
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Karimi A, Razaghi R, Biglari H, Sabbaghi H, Sera T, Kudo S. A comparative study to determine the optimal intravitreal injection angle to the eye: A computational fluid-structure interaction model. Technol Health Care 2018; 26:483-498. [DOI: 10.3233/thc-160777] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- Alireza Karimi
- Department of Mechanical Engineering, Kyushu University, Fukuoka, Japan
| | - Reza Razaghi
- Department of Mechanical Engineering, University of Tabriz, Tabriz, Iran
- Basir Eye Health Research Center, Tehran, Iran
| | - Hasan Biglari
- Department of Mechanical Engineering, University of Tabriz, Tabriz, Iran
| | | | - Toshihiro Sera
- Department of Mechanical Engineering, Kyushu University, Fukuoka, Japan
| | - Susumu Kudo
- Department of Mechanical Engineering, Kyushu University, Fukuoka, Japan
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Rohrbach D, Ito K, Lloyd HO, Silverman RH, Yoshida K, Yamaguchi T, Mamou J. Material Properties of Human Ocular Tissue at 7-µm Resolution. ULTRASONIC IMAGING 2017; 39:313-325. [PMID: 28675987 PMCID: PMC7536713 DOI: 10.1177/0161734617713498] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Quantitative assessment of the material properties of ocular tissues can provide valuable information for investigating several ophthalmic diseases. Quantitative acoustic microscopy (QAM) offers a means of obtaining such information, but few QAM investigations have been conducted on human ocular tissue. We imaged the optic nerve (ON) and iridocorneal angle in 12-µm deparaffinized sections of the human eye using a custom-built acoustic microscope with a 250-MHz transducer (7-µm lateral resolution). The two-dimensional QAM maps of ultrasound attenuation (α), speed of sound ( c), acoustic impedance ( Z), bulk modulus ( K), and mass density (ρ) were generated. Scanned samples were then stained and imaged by light microscopy for comparison with QAM maps. The spatial resolution and contrast of scanning acoustic microscopy (SAM) maps were sufficient to resolve anatomic layers of the retina (Re); anatomic features in SAM maps corresponded to those seen by light microscopy. Significant variations of the acoustic parameters were found. For example, the sclera was 220 MPa stiffer than Re, choroid, and ON tissue. To the authors' knowledge, this is the first systematic study to assess c, Z, K, ρ, and α of human ocular tissue at the high ultrasound frequencies used in this study.
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Koelbl PS, Klante P, Koch F, Lingenfelder C, Werner JU, Enders C, Hessling M. Location and pressure dependent transmission of human and porcine sclera: an anterior to posterior examination. Graefes Arch Clin Exp Ophthalmol 2017; 255:2185-2198. [PMID: 28779364 DOI: 10.1007/s00417-017-3758-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 07/17/2017] [Indexed: 10/19/2022] Open
Abstract
PURPOSE For diaphanoscopy or transscleral laser applications, the transmission of the sclera is an essential property. The study aimed to determine the pressure dependent transmission of human sclera from anterior to posterior. METHODS Pressure dependent transmission measurements were performed by a pressure inducing setup at the range of 60-2058 kPa. The transmissions were measured within spectral range of 350-1100 nm. Specimens of human sclera were taken from corneo-scleral transplants. Those compounds were obtained at pars plicata residual sclera tissue. For an anterior to posterior examination of transmission, samples were taken from halved eye globes, which were formerly fixed in formalin. RESULTS The pressure dependent transmission increased with rising load at all measured wavelengths for human sclera samples. The highest increase was observed for short wavelengths. With rising pressure, the increase of transmission aimed for a steady state. This behavior was fitted by a limited growing function. With an inducing burden of 2058 kPa, the steady state was already reached and exhibited an increase in transmission factor of 4.1 at 400 nm and 1.8 at 1000 nm. The anterior to posterior measurements of human sclera fixed in formalin were not corresponding to the results of the other human samples. For the porcine samples, the transmission increased from anterior to the equator of the eye globe. Further posterior the transmission decreased and rose again to N. opticus. With rising pressure, the transmission increased at all wavelengths and all locations. Posterior from the equator, with higher pressure the transmission became superior compared to anterior. CONCLUSIONS The results of human sclera fixed in formalin could be related to formalin-induced cross-linking between the collagen fibers. Because of doubt about the physiological behavior of formalin-fixed samples, formalin-free porcine postmortem eye globes were also probed having a very similar thickness and histological structure as human sclera, so the results could be set in relation to human probes. These results can now be used to create an eye-map to determine maximum possible retina irradiation or illumination durations for transscleral applications in eye surgery.
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Affiliation(s)
- Philipp Simon Koelbl
- Institute of Medical Engineering and Mechatronics, Ulm University of Applied Sciences, Albert-Einstein-Allee 55, D-89081, Ulm, Germany.
| | - Pia Klante
- Institute of Medical Engineering and Mechatronics, Ulm University of Applied Sciences, Albert-Einstein-Allee 55, D-89081, Ulm, Germany
| | - Frank Koch
- Clinic of Ophthalmology, Goethe University, Theodor-Stern-Kai 7, D-60590, Frankfurt, Germany
| | | | - Jens Ulrich Werner
- Department of Ophthalmology, University of Ulm, Prittwitzstrasse 43, D-89075, Ulm, Germany
| | - Christian Enders
- Department of Ophthalmology, University of Ulm, Prittwitzstrasse 43, D-89075, Ulm, Germany
| | - Martin Hessling
- Institute of Medical Engineering and Mechatronics, Ulm University of Applied Sciences, Albert-Einstein-Allee 55, D-89081, Ulm, Germany
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Karimi A, Razaghi R, Navidbakhsh M, Sera T, Kudo S. Computing the influences of different Intraocular Pressures on the human eye components using computational fluid-structure interaction model. Technol Health Care 2017; 25:285-297. [DOI: 10.3233/thc-161280] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- Alireza Karimi
- Department of Mechanical Engineering, Kyushu University, Fukuoka 819-0395, Japan
| | - Reza Razaghi
- Basir Eye Health Research Center, Tehran 14186, Iran
| | - Mahdi Navidbakhsh
- Department of Biomechanics, Science and Research Branch, Islamic Azad University, Tehran 755/4515, Iran
| | - Toshihiro Sera
- Department of Mechanical Engineering, Kyushu University, Fukuoka 819-0395, Japan
| | - Susumu Kudo
- Department of Mechanical Engineering, Kyushu University, Fukuoka 819-0395, Japan
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Jia X, Yu J, Liao SH, Duan XC. Biomechanics of the sclera and effects on intraocular pressure. Int J Ophthalmol 2016; 9:1824-1831. [PMID: 28003987 DOI: 10.18240/ijo.2016.12.21] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 08/03/2016] [Indexed: 11/23/2022] Open
Abstract
Accumulating evidence indicates that glaucoma is a multifactorial neurodegenerative disease characterized by the loss of retinal ganglion cells (RGC), resulting in gradual and progressive permanent loss of vision. Reducing intraocular pressure (IOP) remains the only proven method for preventing and delaying the progression of glaucomatous visual impairment. However, the specific role of IOP in optic nerve injury remains controversial, and little is known about the biomechanical mechanism by which elevated IOP leads to the loss of RGC. Published studies suggest that the biomechanical properties of the sclera and scleral lamina cribrosa determine the biomechanical changes of optic nerve head, and play an important role in the pathologic process of loss of RGC and optic nerve damage. This review focuses on the current understanding of biomechanics of sclera in glaucoma and provides an overview of the possible interactions between the sclera and IOP. Treatments and interventions aimed at the sclera are also discussed.
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Affiliation(s)
- Xu Jia
- Department of Ophthalmology, the Second Xiangya Hospital, Central South University, Changsha 410011, Hunan Province, China
| | - Juan Yu
- Department of Ophthalmology, the First Hospital of Hunan University of Chinese Medicine, Changsha 410011, Hunan Province, China
| | - Sheng-Hui Liao
- School of Information Science and Engineering, Central South University, Changsha 410011, Hunan Province, China
| | - Xuan-Chu Duan
- Department of Ophthalmology, the Second Xiangya Hospital, Central South University, Changsha 410011, Hunan Province, China
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Vahdati A, Seven I, Mysore N, Randleman JB, Dupps WJ. Computational Biomechanical Analysis of Asymmetric Ectasia Risk in Unilateral Post-LASIK Ectasia. J Refract Surg 2016; 32:811-820. [PMID: 27930791 DOI: 10.3928/1081597x-20160929-01] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Accepted: 08/29/2016] [Indexed: 11/20/2022]
Abstract
PURPOSE To develop a computational approach to corneal biomechanical risk analysis in refractive surgery and to investigate its utility in an enigmatic case of unilateral ectasia after bilateral LASIK. METHODS Preoperative corneal elevation datasets from both eyes of a patient who developed unilateral post-LASIK ectasia were used to construct geometrically patient-specific, microstructurally motivated finite element models. Models were assessed before and after implementation of case-specific treatment parameters for interocular differences in corneal geometry and strain behavior under physiological loading conditions. RESULTS Standard clinical predictors of post-LASIK ectasia risk were similar for the affected and contralateral eyes, and no risk factor asymmetry was identified in tomographic screening that included posterior corneal elevation analysis. However, differences in the magnitude and distribution of strain and stress were observed that are consistent with greater predisposition to biomechanical instability in the affected eye. Load testing with simulated intraocular pressure increases provoked opposite trends in curvature change in the preoperative models representing affected and unaffected eyes, with steepening in the ectatic eye and flattening in the clinically stable eye. CONCLUSIONS Patient-specific computational analyses revealed differences in intrinsic biomechanical behaviors that may predispose a cornea to instability after refractive surgery. Strain and stress analyses elucidated differential risk not ascertained with current refractive surgery screening paradigms. This pilot study illustrates a risk analysis approach that implicitly considers the entire corneal three-dimensional geometry and can be performed a priori in a screening setting. [J Refract Surg. 2016;32(12):811-820.].
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Precise measurement of scleral radius using anterior eye profilometry. Cont Lens Anterior Eye 2016; 40:47-52. [PMID: 27863894 DOI: 10.1016/j.clae.2016.11.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2016] [Revised: 10/14/2016] [Accepted: 11/08/2016] [Indexed: 11/23/2022]
Abstract
PURPOSE To develop a new and precise methodology to measure the scleral radius based on anterior eye surface. METHODS Eye Surface Profiler (ESP, Eaglet-Eye, Netherlands) was used to acquire the anterior eye surface of 23 emmetropic subjects aged 28.1±6.6years (mean±standard deviation) ranging from 20 to 45. Scleral radius was obtained based on the approximation of the topographical scleral data to a sphere using least squares fitting and considering the axial length as a reference point. To better understand the role of scleral radius in ocular biometry, measurements of corneal radius, central corneal thickness, anterior chamber depth and white-to-white corneal diameter were acquired with IOLMaster 700 (Carl Zeiss Meditec AG, Jena, Germany). RESULTS The estimated scleral radius (11.2±0.3mm) was shown to be highly precise with a coefficient of variation of 0.4%. A statistically significant correlation between axial length and scleral radius (R2=0.957, p<0.001) was observed. Moreover, corneal radius (R2=0.420, p<0.001), anterior chamber depth (R2=0.141, p=0.039) and white-to-white corneal diameter (R2=0.146, p=0.036) have also shown statistically significant correlations with the scleral radius. Lastly, no correlation was observed comparing scleral radius to the central corneal thickness (R2=0.047, p=0.161). CONCLUSIONS Three-dimensional topography of anterior eye acquired with Eye Surface Profiler together with a given estimate of the axial length, can be used to calculate the scleral radius with high precision.
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Abstract
OBJECTIVE The aim of this study was to develop computational methods for estimating limbus position based on the measurements of three-dimensional (3-D) corneoscleral topography and ascertain whether corneoscleral limbus routinely estimated from the frontal image corresponds to that derived from topographical information. METHODS Two new computational methods for estimating the limbus position are proposed: One based on approximating the raw anterior eye height data by series of Zernike polynomials and one that combines the 3-D corneoscleral topography with the frontal grayscale image acquired with the digital camera in-built in the profilometer. The proposed methods are contrasted against a previously described image-only-based procedure and to a technique of manual image annotation. RESULTS The estimates of corneoscleral limbus radius were characterized with a high precision. The group average (mean ± standard deviation) of the maximum difference between estimates derived from all considered methods was 0.27 ± 0.14 mm and reached up to 0.55 mm. The four estimating methods lead to statistically significant differences (nonparametric ANOVA (the Analysis of Variance) test, p 0.05). CONCLUSION Precise topographical limbus demarcation is possible either from the frontal digital images of the eye or from the 3-D topographical information of corneoscleral region. However, the results demonstrated that the corneoscleral limbus estimated from the anterior eye topography does not always correspond to that obtained through image-only based techniques. SIGNIFICANCE The experimental findings have shown that 3-D topography of anterior eye, in the absence of a gold standard, has the potential to become a new computational methodology for estimating the corneoscleral limbus.
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Wang LK, Huang YP, Tian L, Kee CS, Zheng YP. Measurement of corneal tangent modulus using ultrasound indentation. ULTRASONICS 2016; 71:20-28. [PMID: 27262352 DOI: 10.1016/j.ultras.2016.05.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Revised: 03/30/2016] [Accepted: 05/16/2016] [Indexed: 06/05/2023]
Abstract
Biomechanical properties are potential information for the diagnosis of corneal pathologies. An ultrasound indentation probe consisting of a load cell and a miniature ultrasound transducer as indenter was developed to detect the force-indentation relationship of the cornea. The key idea was to utilize the ultrasound transducer to compress the cornea and to ultrasonically measure the corneal deformation with the eyeball overall displacement compensated. Twelve corneal silicone phantoms were fabricated with different stiffness for the validation of measurement with reference to an extension test. In addition, fifteen fresh porcine eyes were measured by the developed system in vitro. The tangent moduli of the corneal phantoms calculated using the ultrasound indentation data agreed well with the results from the tensile test of the corresponding phantom strips (R(2)=0.96). The mean tangent moduli of the porcine corneas measured by the proposed method were 0.089±0.026MPa at intraocular pressure (IOP) of 15mmHg and 0.220±0.053MPa at IOP of 30mmHg, respectively. The coefficient of variation (CV) and intraclass correlation coefficient (ICC) of tangent modulus were 14.4% and 0.765 at 15mmHg, and 8.6% and 0.870 at 30mmHg, respectively. The preliminary study showed that ultrasound indentation could be applied to the measurement of corneal tangent modulus with good repeatability and improved measurement accuracy compared to conventional surface displacement-based measurement method. The ultrasound indentation can be a potential tool for the corneal biomechanical properties measurement in vivo.
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Affiliation(s)
- Li-Ke Wang
- Interdisciplinary Division of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong, China
| | - Yan-Ping Huang
- Interdisciplinary Division of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong, China
| | - Lei Tian
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology & Visual Sciences Key Laboratory, Beijing, China
| | - Chea-Su Kee
- Interdisciplinary Division of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong, China; School of Optometry, The Hong Kong Polytechnic University, Hong Kong, China
| | - Yong-Ping Zheng
- Interdisciplinary Division of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong, China.
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Loewen RT, Roy P, Park DB, Jensen A, Scott G, Cohen-Karni D, Fautsch MP, Schuman JS, Loewen NA. A Porcine Anterior Segment Perfusion and Transduction Model With Direct Visualization of the Trabecular Meshwork. Invest Ophthalmol Vis Sci 2016; 57:1338-44. [PMID: 27002293 PMCID: PMC4811178 DOI: 10.1167/iovs.15-18125] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Purpose To establish a consistent and affordable, high quality porcine anterior segment perfusion and transduction model that allows direct visualization of the trabecular meshwork. Methods Porcine anterior segments were cultured within 2 hours of death by removing lens and uvea and securing in a specially designed petri dish with a thin bottom to allow direct visualization of the trabecular meshwork with minimal distortion. Twenty-two control eyes (CO) with a constant flow rate were compared to eight gravity perfused eyes (COgr, 15 mm Hg). We established gene delivery to the TM using eGFP expressing feline immunodeficiency virus (FIV) vector GINSIN at 108 transducing units (TU) per eye (GINSIN_8, n = 8) and 107 TU (GINSIN_7, n = 8). Expression was assessed for 14 days before histology was obtained. Results Pig eyes were a reliable source for consistent and high quality anterior segment cultures with a low failure rate of 12%. Control eyes had an intraocular pressure (IOP) of 15.8 ± 1.9 mm Hg at fixed pump perfusion with 3 μL/min compared to gravity perfused COgr with imputed 3.7 ± 1.6 μL/min. Vector GINSIN_8 eyes experienced a transient posttransduction IOP increase of 44% that resolved at 48 hours; this was not observed in GINSIN_7 eyes. Expression was higher in GINSIN_8 than in GINSIN_7 eyes. Trabecular meshwork architecture was well preserved. Conclusions Compared with previously used human donor eyes, this inexpensive porcine anterior segment perfusion model is of sufficient, repeatable high quality to develop strategies of TM bioengineering. Trabecular meshwork could be observed directly. Despite significant anatomic differences, effects of transduction replicate the main aspects of previously explored human, feline and rodent models.
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Affiliation(s)
- Ralitsa T Loewen
- Department of Ophthalmology University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Pritha Roy
- Department of Ophthalmology University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Daniel B Park
- Department of Ophthalmology University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Adrianna Jensen
- Department of Ophthalmology University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Gordon Scott
- Department of Ophthalmology University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Devora Cohen-Karni
- Department of Ophthalmology University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Michael P Fautsch
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, United States
| | - Joel S Schuman
- Department of Ophthalmology University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Nils A Loewen
- Department of Ophthalmology University of Pittsburgh, Pittsburgh, Pennsylvania, United States
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Feng P, Li X, Chen W, Liu C, Rong S, Wang X, Du G. Combined effects of interleukin-1β and cyclic stretching on metalloproteinase expression in corneal fibroblasts in vitro. Biomed Eng Online 2016; 15:63. [PMID: 27286674 PMCID: PMC4901398 DOI: 10.1186/s12938-016-0198-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Accepted: 06/01/2016] [Indexed: 01/26/2023] Open
Abstract
Background Corneal tensile strain increases if the cornea becomes thin or if intraocular pressure increases. However, the effects of mechanical stress on extracellular matrix (ECM) remodelling in the corneal repair process and the corneal anomalies are unknown. Methods In this study, the combined effects of interleukin-1β (IL-1β) on matrix metalloproteinases (MMPs) in corneal fibroblasts under cyclic stretching were investigated in vitro. Cultured rabbit corneal fibroblasts were subjected to 5, 10 or 15 % cyclic equibiaxial stretching at 0.1 Hz for 36 h in the presence of IL-1β. Conditioned medium was harvested for the analysis of MMP2 and MMP9 protein production using the gelatin zymography and western blot techniques. Results and conclusions Cyclic equibiaxial stretching changed the cell morphology by increasing the contractility of F-actin fibres. IL-1β alone induced the expression of MMP9 and increased the production of MMP2, and 5 % stretching alone decreased the production of MMP2, which indicates that a low stretching magnitude can reduce ECM degradation. In the presence of IL-1β, 5 and 10 % stretching increased the production of MMP2, whereas 15 % stretching increased the production of MMP9. These results indicate that MMP expression is enhanced by cyclic mechanical stimulation in the presence of IL-1β, which is expected to contribute to corneal ECM degradation, leading to the development of post-refractive surgery keratectasia.
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Affiliation(s)
- Pengfei Feng
- Institute of Applied Mechanics and Biomedical Engineering, Taiyuan University of Technology, Taiyuan, 030024, China
| | - Xiaona Li
- Institute of Applied Mechanics and Biomedical Engineering, Taiyuan University of Technology, Taiyuan, 030024, China.
| | - Weiyi Chen
- Institute of Applied Mechanics and Biomedical Engineering, Taiyuan University of Technology, Taiyuan, 030024, China.
| | - Chengxing Liu
- Biology Department, Taiyuan Normal University, Jinzhong, 030619, China
| | - Shuo Rong
- Institute of Applied Mechanics and Biomedical Engineering, Taiyuan University of Technology, Taiyuan, 030024, China
| | - Xiaojun Wang
- College of Mechanics, Taiyuan University of Technology, Taiyuan, 030024, China
| | - Genlai Du
- Institute of Applied Mechanics and Biomedical Engineering, Taiyuan University of Technology, Taiyuan, 030024, China
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Exler RE, Guo X, Chan D, Livne-Bar I, Vicic N, Flanagan JG, Sivak JM. Biomechanical insult switches PEA-15 activity to uncouple its anti-apoptotic function and promote erk mediated tissue remodeling. Exp Cell Res 2016; 340:283-94. [DOI: 10.1016/j.yexcr.2015.11.023] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 10/27/2015] [Accepted: 11/21/2015] [Indexed: 11/15/2022]
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HEICHEL J, WILHELM F, KUNERT KS, HAMMER T. Topographic Findings of the Porcine Cornea. MEDICAL HYPOTHESIS, DISCOVERY & INNOVATION OPHTHALMOLOGY JOURNAL 2016; 5:125-131. [PMID: 28293660 PMCID: PMC5346302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 10/29/2022]
Abstract
The porcine eye is often used as an ex vivo animal model in ophthalmological research. It is well suited for investigations concerning refractive surgery; however, corneal topography data are scarce. This study investigated the corneal topography and pachymetry of the porcine eye to provide further reproducible data. We evaluated freshly enucleated porcine eyes (n = 16) by performing computerized corneal topographies (Orbscan® IIz, Bausch and Lomb, Rochester, NY, USA). We assessed the steepest and flattest keratometric powers (K1 and K2, units in diopters (D)), astigmatism (D), white-to-white (WTW) diameter (mm), thinnest point pachymetry (µm), anterior and posterior best-fit sphere (BFS) (D), refractive power of the anterior and posterior curvatures, and total refractive power of the cornea (D). The mean keratometric powers were 39.6 ± 0.89 D (K1) and 38.5 ± 0.92 D (K2), and the mean astigmatism was 1.1 ± 0.78 D. The mean WTW diameter was 13.81 ± 0.83 mm, and the mean corneal thickness was 832.6 ± 40.18 µm. The BFSs were 38.14 ± 0.73 D (anterior) and 42.56 ± 1.15 D (posterior), and the mean refractive powers were 43.27 ± 1.08 D (anterior) and -5.15 ± 0.20 D (posterior); therefore, the mean of the total refractive power was 38.16 ± 1.00 D. The topography and pachymetry of the porcine cornea showed a specific configuration differing from the human cornea. When using animal ex vivo models such as porcine corneas for experimental corneal surgery, findings such as these should be considered.
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Affiliation(s)
- Jens HEICHEL
- Department of Ophthalmology, University Hospital of Martin Luther, University Halle-Wittenberg, Halle (Saale), Germany
| | | | | | - Thomas HAMMER
- Department of Ophthalmology, University Hospital of Martin Luther, University Halle-Wittenberg, Halle (Saale), Germany,Augenzentrum Frohe Zukunft, Halle (Saale), Germany
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Kim YJ, Park SH, Choi KS. FLUCTUATION OF INFUSION PRESSURE DURING MICROINCISION VITRECTOMY USING THE CONSTELLATION VISION SYSTEM. Retina 2015; 35:2529-36. [PMID: 26035515 DOI: 10.1097/iae.0000000000000625] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE To measure fluctuations in infusion pressure and intraocular pressure (IOP) during vitrectomy performed using a flow-based IOP control system. METHODS Using 3 vitrectomized porcine eyes, the authors simultaneously measured infusion pressure and IOP during vitreous cutting and aspiration and after extraction of operative instruments in 23-gauge and 25-gauge system. The measurements were performed with the "IOP control" setting turned on or off. The efficacy of valved cannula and a built-in "IOP control limit" module in attenuation of infusion pressure fluctuation was evaluated. RESULTS At set pressure of 30 mmHg and 60 mmHg, the mean infusion pressure levels were 43.7 mmHg and 78.7 mmHg in the vitreous cutting mode, 67.4 mmHg and 101.2 mmHg in the aspiration mode, and 72.8 mmHg and 115.8 mmHg after extraction of the operative instrument, respectively, when the 23-gauge system was used. Use of valved cannulas effectively attenuated fluctuations in both infusion pressure and IOP. When the IOP control limit setting was "on," the compensatory infusion pressure increase was markedly limited and similar to the set pressure level when the IOP control limit was set at Level 2. Similar results were obtained when a 25-gauge system was used. CONCLUSION Infusion pressure increased markedly during vitrectomy using a flow-based IOP control system.
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Affiliation(s)
- Yong Joon Kim
- Department of Ophthalmology, Soonchunhyang University College of Medicine, Soonchunhyang University Seoul Hospital, Seoul, Republic of Korea
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Millar JC, Pang IH. Non-continuous measurement of intraocular pressure in laboratory animals. Exp Eye Res 2015; 141:74-90. [PMID: 25933714 DOI: 10.1016/j.exer.2015.04.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Revised: 04/21/2015] [Accepted: 04/27/2015] [Indexed: 01/02/2023]
Abstract
Glaucoma is a leading cause of blindness, which is treatable but currently incurable. Numerous animal models therefore have both been and continue to be utilized in the study of numerous aspects of this condition. One important facet associated with the use of such models is the ability to accurately and reproducibly measure (by cannulation) or estimate (by tonometry) intraocular pressure (IOP). At this juncture there are several different approaches to IOP measurement in different experimental animal species, and the list continues to grow. We feel therefore that a review of this subject matter is timely and should prove useful to others who wish to perform similar measurements. The general principles underlying various types of tonometric and non-tonometric techniques for non-continuous determination of IOP are considered. There follows discussion of specific details as to how these techniques are applied to experimental animal species involved in the research of this disease. Specific comments regarding anesthesia, circadian rhythm, and animal handling are also included, especially in the case of rodents. Brief consideration is also given to possible future developments.
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Affiliation(s)
- J Cameron Millar
- North Texas Eye Research Institute (NTERI), University of North Texas Health Science Center (UNTHSC), 3500 Camp Bowie Boulevard, Fort Worth, TX 76107, USA; Department of Cell Biology and Immunology, University of North Texas Health Science Center (UNTHSC), 3500 Camp Bowie Boulevard, Fort Worth, TX 76107, USA.
| | - Iok-Hou Pang
- North Texas Eye Research Institute (NTERI), University of North Texas Health Science Center (UNTHSC), 3500 Camp Bowie Boulevard, Fort Worth, TX 76107, USA; Department of Cell Biology and Immunology, University of North Texas Health Science Center (UNTHSC), 3500 Camp Bowie Boulevard, Fort Worth, TX 76107, USA; Department of Pharmaceutical Sciences, University of North Texas Health Science Center (UNTHSC), 3500 Camp Bowie Boulevard, Fort Worth, TX 76107, USA
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Kim YJ, Choi KS. Pressure difference between the anterior chamber and the vitreous cavity in eyes with pupillary block. Curr Eye Res 2014; 40:572-8. [PMID: 25014633 DOI: 10.3109/02713683.2014.939764] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE The purpose of this study was to measure the pressure difference between the anterior chamber (AC) and the vitreous cavity (VC) in eyes with and without pupillary block. MATERIALS AND METHODS Seven vitrectomized porcine eyes were used. Infusion pressures of 10-80 mmHg were generated with a vented gas forced infusion system. Measurements of pressure were obtained with digital manometry connected to 25-gauge catheters from the AC and VC simultaneously. After increasing AC pressure to each target pressure, VC pressure was recorded, and vice versa. Inspection was performed with portable slit-lamp biomicroscopy to identify the development of pupillary block at the end of each experiment. RESULTS When the AC pressure was increased, the VC pressure obtained was similar to the AC pressure in all cases. When the VC pressure increased, the AC pressure obtained was similar to that at a VC pressure of less than 50 mmHg. When the VC pressure was increased rapidly to 60, 70, and 80 mmHg, the AC pressures obtained were 57.6 ± 1.0, 64.0 ± 0.8, and 69.6 ± 2.4 mmHg, respectively. Thus, the VC pressures obtained were 1.5, 5.9, and 9.1 mmHg higher than pressures obtained from AC with target pressures of 60, 70, and 80 mmHg, respectively (p = 0.027, 0.001, and 0.001, respectively). Pupillary block was observed in cases where the VC pressure was increased to more than 50 mmHg. CONCLUSIONS The AC pressure could be significantly lower than the VC pressure in some eyes with pupillary block.
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Affiliation(s)
- Yong Joon Kim
- Department of Ophthalmology, Soonchunhyang University College of Medicine, Soonchunhyang University Seoul Hospital , Seoul , Republic of Korea
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Yamanari M, Nagase S, Fukuda S, Ishii K, Tanaka R, Yasui T, Oshika T, Miura M, Yasuno Y. Scleral birefringence as measured by polarization-sensitive optical coherence tomography and ocular biometric parameters of human eyes in vivo. BIOMEDICAL OPTICS EXPRESS 2014; 5:1391-402. [PMID: 24877003 PMCID: PMC4026890 DOI: 10.1364/boe.5.001391] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Revised: 03/26/2014] [Accepted: 03/31/2014] [Indexed: 05/03/2023]
Abstract
The relationship between scleral birefringence and biometric parameters of human eyes in vivo is investigated. Scleral birefringence near the limbus of 21 healthy human eyes was measured using polarization-sensitive optical coherence tomography. Spherical equivalent refractive error, axial eye length, and intraocular pressure (IOP) were measured in all subjects. IOP and scleral birefringence of human eyes in vivo was found to have statistically significant correlations (r = -0.63, P = 0.002). The slope of linear regression was -2.4 × 10(-2) deg/μm/mmHg. Neither spherical equivalent refractive error nor axial eye length had significant correlations with scleral birefringence. To evaluate the direct influence of IOP to scleral birefringence, scleral birefringence of 16 ex vivo porcine eyes was measured under controlled IOP of 5-60 mmHg. In these ex vivo porcine eyes, the mean linear regression slope between controlled IOP and scleral birefringence was -9.9 × 10(-4) deg/μm/mmHg. In addition, porcine scleral collagen fibers were observed with second-harmonic-generation (SHG) microscopy. SHG images of porcine sclera, measured on the external surface at the superior side to the cornea, showed highly aligned collagen fibers parallel to the limbus. In conclusion, scleral birefringence of healthy human eyes was correlated with IOP, indicating that the ultrastructure of scleral collagen was correlated with IOP. It remains to show whether scleral collagen ultrastructure of human eyes is affected by IOP as a long-term effect.
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Affiliation(s)
- Masahiro Yamanari
- Computational Optics Group, University of Tsukuba, Tsukuba, Ibaraki, Japan
- Computational Optics and Ophthalmology Group, Tsukuba, Ibaraki, Japan
- Tomey Corporation, Nagoya, Aichi, Japan
| | - Satoko Nagase
- Department of Ophthalmology, Tokyo Medical University Ibaraki Medical Center, Ami, Ibaraki, Japan
- Computational Optics and Ophthalmology Group, Tsukuba, Ibaraki, Japan
| | - Shinichi Fukuda
- Department of Ophthalmology, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan
- Computational Optics and Ophthalmology Group, Tsukuba, Ibaraki, Japan
| | - Kotaro Ishii
- Department of Ophthalmology, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan
- Computational Optics and Ophthalmology Group, Tsukuba, Ibaraki, Japan
| | - Ryosuke Tanaka
- Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan
| | - Takeshi Yasui
- Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan
- Institute of Technology and Science, The University of Tokushima, Tokushima, Tokushima, Japan
| | - Tetsuro Oshika
- Department of Ophthalmology, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan
- Computational Optics and Ophthalmology Group, Tsukuba, Ibaraki, Japan
| | - Masahiro Miura
- Department of Ophthalmology, Tokyo Medical University Ibaraki Medical Center, Ami, Ibaraki, Japan
- Computational Optics and Ophthalmology Group, Tsukuba, Ibaraki, Japan
| | - Yoshiaki Yasuno
- Computational Optics Group, University of Tsukuba, Tsukuba, Ibaraki, Japan
- Computational Optics and Ophthalmology Group, Tsukuba, Ibaraki, Japan
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Pallikaris IG, Dastiridou AI, Tsilimbaris MK, Karyotakis NG, Ginis HS. Ocular rigidity. EXPERT REVIEW OF OPHTHALMOLOGY 2014. [DOI: 10.1586/eop.10.30] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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