1
|
Srikantha N, Teijeiro-Gonzalez Y, Simpson A, Elsaid N, Somavarapu S, Suhling K, Jackson TL. Determining vitreous viscosity using fluorescence recovery after photobleaching. PLoS One 2022; 17:e0261925. [PMID: 35143514 PMCID: PMC8830689 DOI: 10.1371/journal.pone.0261925] [Citation(s) in RCA: 2] [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: 05/30/2021] [Accepted: 12/14/2021] [Indexed: 01/22/2023] Open
Abstract
PURPOSE Vitreous humor is a complex biofluid whose composition determines its structure and function. Vitreous viscosity will affect the delivery, distribution, and half-life of intraocular drugs, and key physiological molecules. The central pig vitreous is thought to closely match human vitreous viscosity. Diffusion is inversely related to viscosity, and diffusion is of fundamental importance for all biochemical reactions. Fluorescence Recovery After Photobleaching (FRAP) may provide a novel means of measuring intravitreal diffusion that could be applied to drugs and physiological macromolecules. It would also provide information about vitreous viscosity, which is relevant to drug elimination, and delivery. METHODS Vitreous viscosity and intravitreal macromolecular diffusion of fluorescently labelled macromolecules were investigated in porcine eyes using fluorescence recovery after photobleaching (FRAP). Fluorescein isothiocyanate conjugated (FITC) dextrans and ficolls of varying molecular weights (MWs), and FITC-bovine serum albumin (BSA) were employed using FRAP bleach areas of different diameters. RESULTS The mean (±standard deviation) viscosity of porcine vitreous using dextran, ficoll and BSA were 3.54 ± 1.40, 2.86 ± 1.13 and 4.54 ± 0.13 cP respectively, with an average of 3.65 ± 0.60 cP. CONCLUSIONS FRAP is a feasible and practical optical method to quantify the diffusion of macromolecules through vitreous.
Collapse
Affiliation(s)
- Nishanthan Srikantha
- School of Medicine, King’s College London, London, United Kingdom
- Department of Ophthalmology, King’s College Hospital, London, United Kingdom
- * E-mail:
| | | | - Andrew Simpson
- School of Medicine, King’s College London, London, United Kingdom
- Department of Ophthalmology, King’s College Hospital, London, United Kingdom
| | - Naba Elsaid
- Anglia Ruskin University, Bishop Hall Lane, Chelmsford, United Kingdom
| | - Satyanarayana Somavarapu
- Department of Pharmaceutics, University College London School of Pharmacy, London, United Kingdom
| | - Klaus Suhling
- Department of Physics, King’s College London, Strand, London, United Kingdom
| | - Timothy L. Jackson
- School of Medicine, King’s College London, London, United Kingdom
- Department of Ophthalmology, King’s College Hospital, London, United Kingdom
| |
Collapse
|
2
|
Biocompatibility of intraocular liquid tamponade agents: an update. Eye (Lond) 2021; 35:2699-2713. [PMID: 34035489 PMCID: PMC8452761 DOI: 10.1038/s41433-021-01596-w] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 04/28/2021] [Accepted: 05/05/2021] [Indexed: 02/04/2023] Open
Abstract
Intraocular liquids tamponade agents, such as perfluorocarbon liquids (PFCLs), semifluorinated alkanes (SFAs), silicone oils (SOs) and heavy silicone oils (HSOs), are a crucial intraoperative and/or postoperative tool in vitreoretinal surgery, in particular for the management of complex vitreoretinal diseases. However, their use is not without complications, which are potentially severe. Consequently, a growing interest has been devoted to the biocompatibility of these compounds and the adequacy of current regulations that should guarantee their safety. Obviously, an updated knowledge on research findings and potential risks associated to the use of intraocular liquid compounds is essential, not only for vitreoretinal surgeons, but also for any ophthalmologist involved in the management of patients receiving intraocular liquid tamponades. In light of this, the review provides a comprehensive characterisation of intraocular liquid tamponades, in terms of physical and chemical properties, current clinical use and possible complications. Moreover, this review focuses on the safety profile of these compounds, summarising the existing regulation and the available evidence on their biocompatibility.
Collapse
|
3
|
Wang T, Ran R, Ma Y, Zhang M. Polymeric hydrogel as a vitreous substitute: current research, challenges, and future directions. Biomed Mater 2021; 16. [PMID: 34038870 DOI: 10.1088/1748-605x/ac058e] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 05/26/2021] [Indexed: 02/08/2023]
Abstract
Vitreoretinal surgery is an essential approach to treat proliferative diabetic vitreopathy, retinal detachment, retinal tear, ocular trauma, and macular holes. The removal of the natural vitreous and the replacement with substitutes are critical steps for retina reattachment. Vitreous substitutes including silicone oil (SiO), air, sulfur hexafluoride (SF6), and perfluoropropane (C3F8), have been widely applied in clinical practice. However, these substitutes are reported to cause complications such as emulsification, high intraocular pressure, and lens opacification. Polymeric hydrogels are a kind of material with favorable physical, mechanical properties, and adaptable biocompatibility, thus being highly expected to be ideal vitreous substitutes. Despite years of research, very few polymeric hydrogels can be applied practically in the vitreous cavity. In this review, we focus on the development of polymeric natural-based hydrogels and synthetic hydrogels. Particularly, we pay attention to recent advances in the novel stimuli-response and self-assembly supramolecular hydrogels. Characterized by easy injectability and long residence time, this kind of hydrogel becomes the potentially promising candidates for ideal vitreous substitutes. Finally, we evaluate the current challenges and provide the future directions of vitreous substitutes.
Collapse
Affiliation(s)
- Ting Wang
- Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu 610041, People's Republic of China.,West China School of Medicine, West China Hospital, Sichuan University, Chengdu 610041, People's Republic of China
| | - Ruijin Ran
- Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu 610041, People's Republic of China.,Minda Hospital of Hubei Minzu University, Enshi, People's Republic of China
| | - Yan Ma
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, People's Republic of China
| | - Ming Zhang
- Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu 610041, People's Republic of China
| |
Collapse
|
4
|
Tram NK, Maxwell CJ, Swindle-Reilly KE. Macro- and Microscale Properties of the Vitreous Humor to Inform Substitute Design and Intravitreal Biotransport. Curr Eye Res 2020; 46:429-444. [PMID: 33040616 DOI: 10.1080/02713683.2020.1826977] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Research on the vitreous humor and development of hydrogel vitreous substitutes have gained a rapid increase in interest within the past two decades. However, the properties of the vitreous humor and vitreous substitutes have yet to be consolidated. In this paper, the mechanical properties of the vitreous humor and hydrogel vitreous substitutes were systematically reviewed. The number of publications on the vitreous humor and vitreous substitutes over the years, as well as their respective testing conditions and testing techniques were analyzed. The mechanical properties of the human vitreous were found to be most similar to the vitreous of pigs and rabbits. The storage and loss moduli of the hydrogel vitreous substitutes developed were found to be orders of magnitude higher in comparison to the native human vitreous. However, the reported modulus for human vitreous, which was most commonly tested in vitro, has been hypothesized to be different in vivo. Future studies should focus on testing the mechanical properties of the vitreous in situ or in vivo. In addition to its mechanical properties, the vitreous humor has other biotransport mechanisms and biochemical functions that establish a redox balance and maintain an oxygen gradient inside the vitreous chamber to protect intraocular tissues from oxidative damage. Biomimetic hydrogel vitreous substitutes have the potential to provide ophthalmologists with additional avenues for treating and controlling vitreoretinal diseases while preventing complications after vitrectomy. Due to the proximity and interconnectedness of the vitreous humor to other ocular tissues, particularly the lens and the retina, more interest has been placed on understanding the properties of the vitreous humor in recent years. A better understanding of the properties of the vitreous humor will aid in improving the design of biomimetic vitreous substitutes and enhancing intravitreal biotransport.
Collapse
Affiliation(s)
- Nguyen K Tram
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Courtney J Maxwell
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Katelyn E Swindle-Reilly
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA.,William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, USA.,Department of Ophthalmology & Visual Science, The Ohio State University, Columbus, OH, USA
| |
Collapse
|
5
|
Bayat J, Emdad H, Abouali O. 3D numerical investigation of the fluid mechanics in a partially liquefied vitreous humor due to saccadic eye movement. Comput Biol Med 2020; 125:103955. [DOI: 10.1016/j.compbiomed.2020.103955] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2019] [Revised: 07/31/2020] [Accepted: 07/31/2020] [Indexed: 10/23/2022]
|
6
|
Stocchino A, Nepita I, Repetto R, Dodero A, Castellano M, Ferrara M, Romano MR. Fluid Dynamic Assessment of Hypersonic and Guillotine Vitrectomy Probes in Viscoelastic Vitreous Substitutes. Transl Vis Sci Technol 2020; 9:9. [PMID: 32821506 PMCID: PMC7409383 DOI: 10.1167/tvst.9.6.9] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Accepted: 03/11/2020] [Indexed: 12/18/2022] Open
Abstract
Purpose To assess the fluidics of 23-gauge (G) large-port (L) and tear drop-port (TD) hypersonic vitrectomy probes (HVPs) compared with guillotine vitrectomy probes (GVPs) of various calibers (23G, 25G, and 27G) and geometries (single and double blades). Also, to identify the working parameters that provide the best balance between acceleration and flow rate, and, for HVPs, to measure temperature variations in the fluid. Methods We used particle image velocimetry to measure flow fields in balanced salt solution and viscoelastic artificial vitreous. We analyzed acceleration, kinetic energy, and volumetric flux. The parameters considered were vacuum pressure, ultrasound stroke, and cut rate. Temperature measurements were taken using an infrared thermal camera. Results The flow rate was significantly higher for HVPs than GVPs. With both probes, flow rate and acceleration increased with vacuum pressure. Flow rate depended weakly on the ultrasound stroke or cut rate. In HVPs, the acceleration peaked at a stroke of 30 µm, whereas in GVPs it peaked at a cutting rate of 4000 to 5000 cuts per minute (cpm). The HPV/TD combination generated higher flow rates and lower accelerations than did HPV/L. The increase in temperature was small. Conclusions Under the present experimental setup and medium, HVPs offered better fluidics compared with GVPs in terms of flow and acceleration; however, the flow structure for HVPs is more complicated and unsteady. The HPV/TD combination produced larger flows than did the HPV/L combination and slightly smaller accelerations. HPVs generated a small temperature increase. Translational Relevance In the tested artificial vitreous, HVPs were found to be more efficient in terms of generating lower acceleration for a given flow rate. The slight increase in temperature observed with HVPs is unlikely to be clinically significant.
Collapse
Affiliation(s)
- Alessandro Stocchino
- Department of Civil, Chemical and Environmental Engineering, University of Genoa, Genoa, Italy
| | - Irene Nepita
- Department of Civil, Chemical and Environmental Engineering, University of Genoa, Genoa, Italy
| | - Rodolfo Repetto
- Department of Civil, Chemical and Environmental Engineering, University of Genoa, Genoa, Italy
| | - Andrea Dodero
- Department of Chemistry and Industrial Chemistry, University of Genoa, Genoa, Italy
| | - Maila Castellano
- Department of Chemistry and Industrial Chemistry, University of Genoa, Genoa, Italy
| | | | - Mario R Romano
- Eye Center, Humanitas Gavazzeni-Castelli, Bergamo, Italy.,Department of Biomedical Sciences, Humanitas University, Milano, Italy
| |
Collapse
|
7
|
Thakur SS, Pan X, Kumarasinghe GL, Yin N, Pontré BP, Vaghefi E, Rupenthal ID. Relationship between rheological properties and transverse relaxation time (T2) of artificial and porcine vitreous humour. Exp Eye Res 2020; 194:108006. [DOI: 10.1016/j.exer.2020.108006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 03/12/2020] [Accepted: 03/13/2020] [Indexed: 12/20/2022]
|
8
|
Kharlap SI, Salikhova AR, Miroshnik NV, Sherstneva LV. [Asteroid hyalosis]. Vestn Oftalmol 2019; 135:286-292. [PMID: 31691674 DOI: 10.17116/oftalma2019135052286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The article analyzes existing information on clinical and experimental studies of vitreous changes in asteroid hyalosis, historical aspects of how this condition was studied over the past hundred years, its occurrence and pathogenesis. Results of various studies were used to evaluate current understanding of the forms and elemental composition of phospholipid mineral sedimentation on vitreous structures and methods of its examination. The problem of intravital assessment of the condition of vitreous body was analyzed, and a method was suggested for studying the macrostructure of hyaloid tracts and the state of the vitreous body by means of digital ultrasound in patients with asteroid hyalosis.
Collapse
Affiliation(s)
- S I Kharlap
- Research Institute of Eye Diseases, 11A Rossolimo St., Moscow, Russian Federation, 119021
| | - A R Salikhova
- Research Institute of Eye Diseases, 11A Rossolimo St., Moscow, Russian Federation, 119021
| | - N V Miroshnik
- Research Institute of Eye Diseases, 11A Rossolimo St., Moscow, Russian Federation, 119021
| | - L V Sherstneva
- I.M. Sechenov First Moscow State Medical University, Department of Ophthalmology, 8-2 Trubetskaya St., Moscow, Russian Federation, 119991
| |
Collapse
|
9
|
Rangchian A, Francone A, Farajzadeh M, Hosseini H, Connelly K, Hubschman JP, Kavehpour HP. Effects of Collagenase Type II on Vitreous Humor—An In Situ Rheological Study. J Biomech Eng 2019; 141:2730407. [DOI: 10.1115/1.4043358] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Indexed: 01/02/2023]
Abstract
The purpose of this study is to quantify the impact of enzyme activity on the vitreous humor structure over time to understand the mechanical characteristics of the vitreous humor gel. Changes in the mechanical behavior of the vitreous occur due to many reasons including aging, which may lead to many vitreoretinal diseases. The degeneration process of the vitreous has been studied; however, in situ experimental procedures to validate the existing hypotheses are limited. We examined thirty-eight porcine eyes using in situ rheological creep tests to measure the mechanical properties of the vitreous humor of the eyes prior to, 1 h and 24 h after the intravitreal injection. Eyes in one group were injected with collagenase type II solution and eyes in the control group were injected with phosphate buffered saline solution (PBS) with calcium and magnesium chloride. Prior to the injection, viscosity and creep compliance intercept values between both groups were not statistically different. At 1 h and 24 h after the injection, vitreous properties in the eyes from the first group showed a statistically significant increase in the J intercept values (representing the inverse of elasticity) compared to the control group. In addition, 1 h and 24 h after the injection, vitreous viscosity was lower in the eyes from the first group than in the eyes from the control group. These findings are a foundation for future studies on the effectiveness of intravitreal drugs that modify the mechanical properties of the vitreous humor.
Collapse
Affiliation(s)
- Aysan Rangchian
- Department of Bioengineering, Complex Fluid and Interfacial Physics Laboratory, University of California Los Angeles, Los Angeles, CA 90095-1597 e-mail:
| | - Anibal Francone
- Retina Division, Stein Eye Institute, University of California Los Angeles, Los Angeles, CA 90095 e-mail:
| | - Matthew Farajzadeh
- Retina Division, Stein Eye Institute, University of California Los Angeles, Los Angeles, CA 90095 e-mail:
| | - Helia Hosseini
- Department of Mechanical and Aerospace Engineering, University of California Los Angeles, Tehran University of Medical Sciences, Tehran 1416753955, Iran e-mail:
| | - Kelly Connelly
- Department of Mechanical and Aerospace Engineering, University of California Los Angeles, Los Angeles, CA 90095 e-mail:
| | - Jean-Pierre Hubschman
- Retina Division, Stein Eye Institute, University of California Los Angeles, Los Angeles, CA 90095 e-mail:
| | - H. Pirouz Kavehpour
- Department of Mechanical and Aerospace Engineering, University of California Los Angeles, Los Angeles, CA 90095; Department of Bioengineering, University of California Los Angeles, Los Angeles, CA 90095 e-mail:
| |
Collapse
|
10
|
Urs R, Ketterling JA, Silverman RH. Ultrafast Ultrasound Imaging of Ocular Anatomy and Blood Flow. Invest Ophthalmol Vis Sci 2017; 57:3810-6. [PMID: 27428169 PMCID: PMC5015817 DOI: 10.1167/iovs.16-19538] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Purpose Ophthalmic ultrasound imaging is currently performed with mechanically scanned single-element probes. These probes have limited capabilities overall and lack the ability to image blood flow. Linear-array systems are able to detect blood flow, but these systems exceed ophthalmic acoustic intensity safety guidelines. Our aim was to implement and evaluate a new linear-array–based technology, compound coherent plane-wave ultrasound, which offers ultrafast imaging and depiction of blood flow at safe acoustic intensity levels. Methods We compared acoustic intensity generated by a 128-element, 18-MHz linear array operated in conventionally focused and plane-wave modes and characterized signal-to-noise ratio (SNR) and lateral resolution. We developed plane-wave B-mode, real-time color-flow, and high-resolution depiction of slow flow in postprocessed data collected continuously at a rate of 20,000 frames/s. We acquired in vivo images of the posterior pole of the eye by compounding plane-wave images acquired over ±10° and produced images depicting orbital and choroidal blood flow. Results With the array operated conventionally, Doppler modes exceeded Food and Drug Administration safety guidelines, but plane-wave modalities were well within guidelines. Plane-wave data allowed generation of high-quality compound B-mode images, with SNR increasing with the number of compounded frames. Real-time color-flow Doppler readily visualized orbital blood flow. Postprocessing of continuously acquired data blocks of 1.6-second duration allowed high-resolution depiction of orbital and choroidal flow over the cardiac cycle. Conclusions Newly developed high-frequency linear arrays in combination with plane-wave techniques present opportunities for the evaluation of ocular anatomy and blood flow, as well as visualization and analysis of other transient phenomena such as vessel wall motion over the cardiac cycle and saccade-induced vitreous motion.
Collapse
Affiliation(s)
- Raksha Urs
- Department of Ophthalmology, Columbia University Medical Center, New York, New York, United States
| | - Jeffrey A Ketterling
- Frederic L. Lizzi Center for Biomedical Engineering, Riverside Research, New York, New York, United States
| | - Ronald H Silverman
- Department of Ophthalmology, Columbia University Medical Center, New York, New York, United States 2Frederic L. Lizzi Center for Biomedical Engineering, Riverside Research, New York, New York, United States
| |
Collapse
|
11
|
Hötte GJ, Schaafsma PJ, Botha CP, Wielopolski PA, Simonsz HJ. Visualization of Sliding and Deformation of Orbital Fat During Eye Rotation. Transl Vis Sci Technol 2016; 5:9. [PMID: 27540495 PMCID: PMC4981490 DOI: 10.1167/tvst.5.4.9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 05/30/2016] [Indexed: 11/24/2022] Open
Abstract
Purpose Little is known about the way orbital fat slides and/or deforms during eye movements. We compared two deformation algorithms from a sequence of MRI volumes to visualize this complex behavior. Methods Time-dependent deformation data were derived from motion-MRI volumes using Lucas and Kanade Optical Flow (LK3D) and nonrigid registration (B-splines) deformation algorithms. We compared how these two algorithms performed regarding sliding and deformation in three critical areas: the sclera-fat interface, how the optic nerve moves through the fat, and how the fat is squeezed out under the tendon of a relaxing rectus muscle. The efficacy was validated using identified tissue markers such as the lens and blood vessels in the fat. Results Fat immediately behind the eye followed eye rotation by approximately one-half. This was best visualized using the B-splines technique as it showed less ripping of tissue and less distortion. Orbital fat flowed around the optic nerve during eye rotation. In this case, LK3D provided better visualization as it allowed orbital fat tissue to split. The resolution was insufficient to visualize fat being squeezed out between tendon and sclera. Conclusion B-splines performs better in tracking structures such as the lens, while LK3D allows fat tissue to split as should happen as the optic nerve slides through the fat. Orbital fat follows eye rotation by one-half and flows around the optic nerve during eye rotation. Translational Relevance Visualizing orbital fat deformation and sliding offers the opportunity to accurately locate a region of cicatrization and permit an individualized surgical plan.
Collapse
Affiliation(s)
- Gijsbert J Hötte
- Department of Ophthalmology Erasmus Medical Center, Rotterdam, the Netherlands
| | - Peter J Schaafsma
- Department of Mediamatics, Technical University Delft, Delft, the Netherlands
| | - Charl P Botha
- Department of Mediamatics, Technical University Delft, Delft, the Netherlands ; Department of Radiology, Laboratory for Clinical and Experimental Image Processing, Leiden University Medical Center, Leiden, the Netherlands
| | | | - Huibert J Simonsz
- Department of Ophthalmology Erasmus Medical Center, Rotterdam, the Netherlands
| |
Collapse
|
12
|
STANDARD CUT RATE 25-GAUGE VITRECTOMY VERSUS ULTRAHIGH-SPEED 25-GAUGE SYSTEM IN CORE VITRECTOMY. Retina 2016; 36:1271-4. [DOI: 10.1097/iae.0000000000000924] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
13
|
Agladioglu K, Pekel G, Altintas Kasikci S, Yagci R, Kiroglu Y. An evaluation of ocular elasticity using real-time ultrasound elastography in primary open-angle glaucoma. Br J Radiol 2016; 89:20150429. [PMID: 26838949 DOI: 10.1259/bjr.20150429] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
OBJECTIVE The aim of this study was to compare sonoelastographic findings in the retina-choroid-sclera (RCS) complex and vitreous in glaucomatous and healthy eyes. METHODS For this cross-sectional comparative study, 20 patients with primary open-angle glaucoma and 20 healthy volunteers were recruited. Ultrasound elastography measurements were taken with a sonographic scanner of the RCS complex, anterior vitreous (AV), posterior vitreous (PV), retrobulbar fat tissue (RFT), optic disc (OD) and optic nerve (ON) in each eye. RESULTS The elasticity index of the RCS complex, RFT, OD, ON, AV and PV was similar in both groups (p > 0.05), although the AV/PV strain ratio in the group of patients with glaucoma was significantly higher (p = 0.04). CONCLUSION Glaucoma increases the AV/PV strain ratio. In providing reproducible and consistent values, the real-time elastography (RTE) technique may be helpful in elucidating the mechanisms of glaucoma in some aspects. ADVANCES IN KNOWLEDGE This study can help to evaluate the elasticity of the RCS complex and vitreous in glaucomatous eyes with RTE.
Collapse
Affiliation(s)
- Kadir Agladioglu
- 1 Pamukkale University, Medical School, Department of Radiology, Denizli, Turkey
| | - Gökhan Pekel
- 2 Pamukkale University, Medical School, Department of Ophtalmology, Denizli, Turkey
| | | | - Ramazan Yagci
- 2 Pamukkale University, Medical School, Department of Ophtalmology, Denizli, Turkey
| | - Yilmaz Kiroglu
- 1 Pamukkale University, Medical School, Department of Radiology, Denizli, Turkey
| |
Collapse
|
14
|
Bonfiglio A, Lagazzo A, Repetto R, Stocchino A. An experimental model of vitreous motion induced by eye rotations. EYE AND VISION (LONDON, ENGLAND) 2015; 2:10. [PMID: 26613091 PMCID: PMC4660830 DOI: 10.1186/s40662-015-0020-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Accepted: 04/30/2015] [Indexed: 11/10/2022]
Abstract
BACKGROUND During eye rotations the vitreous humour moves with respect to the eye globe. This relative motion has been suggested to possibly have an important role in inducing degradation of the gel structure, which might lead to vitreous liquefaction and/or posterior vitreous detachment. Aim of the present work is to study the characteristics of vitreous motion induced by eye rotations. METHODS We use an experimental setup, consisting of a Perspex model of the vitreous chamber that, for simplicity, is taken to have a spherical shape. The model is filled with an artificial vitreous humour, prepared as a solution of agar powder and hyaluronic acid sodium salt in deionised water, which has viscoelastic mechanical properties similar to those of the real vitreous. The model rotates about an axis passing through the centre of the sphere and velocity measurements are taken on the equatorial plane orthogonal to the axis of rotation, using an optical technique. RESULTS The results show that fluid viscoelasticity has a strong influence on flow characteristics. In particular, at certain frequencies of oscillation of the eye model, fluid motion can be resonantly excited. This means that fluid velocity within the domain can be significantly larger than that of the wall. CONCLUSIONS The frequencies for which resonant excitation occurs are within the range of possible eye rotations frequencies. Therefore, the present results suggest that resonant excitation of vitreous motion is likely to occur in practice. This, in turn, implies that eye rotations produce large stresses on the retina and within the vitreous that may contribute to the disruption of the vitreous gel structure. The present results also have implications for the choice of the ideal properties for vitreous substitute fluids.
Collapse
Affiliation(s)
- Andrea Bonfiglio
- Department of Civil, Chemical and Environmental Engineering, University of Genoa, Italy, Via Montallegro 1, Genoa, 16145 Italy
| | - Alberto Lagazzo
- Department of Civil, Chemical and Environmental Engineering, University of Genoa, Italy, Via Montallegro 1, Genoa, 16145 Italy
| | - Rodolfo Repetto
- Department of Civil, Chemical and Environmental Engineering, University of Genoa, Italy, Via Montallegro 1, Genoa, 16145 Italy
| | - Alessandro Stocchino
- Department of Civil, Chemical and Environmental Engineering, University of Genoa, Italy, Via Montallegro 1, Genoa, 16145 Italy
| |
Collapse
|
15
|
Filas BA, Shah NS, Zhang Q, Shui YB, Lake SP, Beebe DC. Quantitative imaging of enzymatic vitreolysis-induced fiber remodeling. Invest Ophthalmol Vis Sci 2014; 55:8626-37. [PMID: 25468895 DOI: 10.1167/iovs.14-15225] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
PURPOSE Collagen fiber remodeling in the vitreous body has been implicated in cases of vitreomacular traction, macular hole, and retinal detachment, and also may occur during pharmacologic vitreolysis. The purpose of this study was to evaluate quantitative polarized light imaging (QPLI) as a tool for studying fiber organization in the vitreous and near the vitreoretinal interface in control and enzymatically perturbed conditions. METHODS Fiber alignment was measured in anterior-posterior sections of bovine and porcine vitreous. Additional tests were performed on bovine lenses and nasal-temporal vitreous sections. Effects of proteoglycan degradation on collagen fiber alignment using trypsin and plasmin were assessed at the microstructural level using electron microscopy and at the global level using QPLI. RESULTS Control vitreous showed fiber organization patterns consistent with the literature across multiple-length scales, including the global anterior-posterior coursing of vitreous fibers, as well as local fibers parallel to the equatorial vitreoretinal interface and transverse to the posterior interface. Proteoglycan digestion with trypsin or plasmin significantly increased fiber alignment throughout the vitreous (P < 0.01). The largest changes (3×) occurred in the posterior vitreous where fibers are aligned transverse to the posterior vitreoretinal interface (P < 0.01). CONCLUSIONS Proteoglycan loss due to enzymatic vitreolysis differentially increases fiber alignment at locations where tractions are most common. We hypothesize that a similar mechanism leads to retinal complications during age-related vitreous degeneration. Structural changes to the entire vitreous body (as opposed to the vitreoretinal interface alone) should be evaluated during preclinical testing of pharmacological vitreolysis candidates.
Collapse
Affiliation(s)
- Benjamen A Filas
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri, United States
| | - Nihar S Shah
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri, United States
| | - Qianru Zhang
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri, United States Eye Center, Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Ying-Bo Shui
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri, United States
| | - Spencer P Lake
- Department of Mechanical Engineering and Materials Science, Washington University, St. Louis, Missouri, United States
| | - David C Beebe
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri, United States Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri, United States
| |
Collapse
|
16
|
Abstract
PURPOSE To characterize the fluidics of vitreous cutter port in response to aspiration and blade motion using particle image velocimetry techniques. Diverse surgical scenarios and fluid characteristics were replicated. METHODS The 23-gauge vitreous cutters were immersed in seeded Balanced Salt Solution (BSS) (Alcon, Forth Worth, TX) or egg albumen, and high-speed video was recorded. Fluid velocity, kinetic energy (KE), and acceleration generated by Venturi and peristaltic pumps were measured in aspiration only (200 and 300 mmHg), low-speed vitrectomy (1,600 cuts per minute; 200 mmHg vacuum), and high-speed vitrectomy (3,000 cuts per minute; 300 mmHg vacuum) modes. RESULTS The Venturi pump generated significantly higher KE than peristaltic pump in BSS (P < 0.0001 for each pair), and aspiration only yielded significantly higher KE. Cutting activation generated significant acceleration (P < 0.001), and the peristaltic pump produced higher positive and negative acceleration peaks (P < 0.001) than the Venturi pump. In egg albumen, the peristaltic pump generated significantly more KE than the Venturi pump (P < 0.001) and perturbed a much wider area. Acceleration was higher for the peristaltic pump in low-speed mode (P < 0.001), whereas in high-speed modality, the Venturi pump produced the highest acceleration peaks (P < 0.001). CONCLUSION Pump type and blade motion largely influence velocity, KE, and acceleration. In BSS, the Venturi pump induces higher KE and acceleration, although perturbing fluid less diffusely. In egg albumen, the peristaltic pump perturbed a much wider area and induced a higher KE and acceleration than the Venturi pump, even more so at lower cut rates. As a conclusion, particle image velocimetry allowed precise characterization of fluid velocity in response to cutter activation, suggesting a pragmatic approach to surgical scenarios.
Collapse
|
17
|
Filas BA, Zhang Q, Okamoto RJ, Shui YB, Beebe DC. Enzymatic degradation identifies components responsible for the structural properties of the vitreous body. Invest Ophthalmol Vis Sci 2014; 55:55-63. [PMID: 24222300 DOI: 10.1167/iovs.13-13026] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
PURPOSE Vitreous degeneration contributes to several age-related eye diseases, including retinal detachment, macular hole, macular traction syndrome, and nuclear cataracts. Remarkably little is understood about the molecular interactions responsible for maintaining vitreous structure. The purpose of this study was to measure the structural properties of the vitreous body after enzymatic degradation of selected macromolecules. METHODS Mechanical properties of plugs of bovine and porcine vitreous were analyzed using a rheometer. Oscillatory and extensional tests measured vitreous stiffness and adhesivity, respectively. Major structural components of the vitreous were degraded by incubation overnight in collagenase, trypsin, or hyaluronidase, singly or in combination. Vitreous bodies were also incubated in hyper- or hypotonic saline. Effects of these treatments on the mechanical properties of the vitreous were measured by rheometry. RESULTS Enzymatic digestion of each class of macromolecules decreased the stiffness of bovine vitreous by approximately half (P < 0.05). Differential effects were observed on the damping capacity of the vitreous (P < 0.05), which was shown to correlate with material behavior in extension (P < 0.01). Digestion of hyaluronan significantly decreased the damping capacity of the vitreous and increased adhesivity. Collagen degradation resulted in the opposite effect, whereas digestion of proteins and proteoglycans with trypsin did not alter behavior relative to controls. Osmotic perturbations and double-enzyme treatments further implicated hyaluronan and hyaluronan-associated water as a primary regulator of adhesivity and material behavior in extension. CONCLUSIONS Collagen, hyaluronan, and proteoglycans act synergistically to maintain vitreous stiffness. Hyaluronan is a key mediator of vitreous adhesivity, and mechanical damping is an important factor influencing dynamic vitreous behavior.
Collapse
Affiliation(s)
- Benjamen A Filas
- Department of Ophthalmology & Visual Sciences, Washington University School of Medicine, St. Louis, Missouri
| | | | | | | | | |
Collapse
|
18
|
Yoon S, Aglyamov S, Karpiouk A, Emelianov S. Correspondence: Spatial variations of viscoelastic properties of porcine vitreous humors. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2013; 60:2453-60. [PMID: 24158299 PMCID: PMC5837826 DOI: 10.1109/tuffc.2013.6644747] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Using a microbubble-based acoustic radiation force approach, spatial variations of Young's modulus and shear viscosity of the porcine vitreous humors in two groups--young pigs (6 months old) and mature pigs (2 to 3 years old)--were measured in situ. The measurements in these groups (4 specimens in each group) were performed in several positions along an anterior-to-posterior direction. At each position, microbubbles were generated by focusing a nanosecond pulsed laser beam and the displacement of each microbubble in response to an impulsive acoustic radiation force was measured every 10 µs using a custom-made high-pulse-repetition-frequency ultrasound system. Based on measured dynamics of the microbubble, Young's modulus and shear viscosity at various locations of the vitreous were reconstructed. Young's moduli of the young and mature porcine vitreous at anterior region were the highest, whereas the central region had the lowest values, indicating the clear spatial variations in the vitreous humor elasticity in both groups.
Collapse
|
19
|
Filas BA, Shui YB, Beebe DC. Computational model for oxygen transport and consumption in human vitreous. Invest Ophthalmol Vis Sci 2013; 54:6549-59. [PMID: 24008409 DOI: 10.1167/iovs.13-12609] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
PURPOSE Previous studies that measured liquefaction and oxygen content in human vitreous suggested that exposure of the lens to excess oxygen causes nuclear cataracts. Here, we developed a computational model that reproduced available experimental oxygen distributions for intact and degraded human vitreous in physiologic and environmentally perturbed conditions. After validation, the model was used to estimate how age-related changes in vitreous physiology and structure alter oxygen levels at the lens. METHODS A finite-element model for oxygen transport and consumption in the human vitreous was created. Major inputs included ascorbate-mediated oxygen consumption in the vitreous, consumption at the posterior lens surface, and inflow from the retinal vasculature. Concentration-dependent relations were determined from experimental human data or estimated from animal studies, with the impact of all assumptions explored via parameter studies. RESULTS The model reproduced experimental data in humans, including oxygen partial pressure (Po2) gradients (≈15 mm Hg) across the anterior-posterior extent of the vitreous body, higher oxygen levels at the pars plana relative to the vitreous core, increases in Po2 near the lens after cataract surgery, and equilibration in the vitreous chamber following vitrectomy. Loss of the antioxidative capacity of ascorbate increases oxygen levels 3-fold at the lens surface. Homogeneous vitreous degeneration (liquefaction), but not partial posterior vitreous detachment, greatly increases oxygen exposure to the lens. CONCLUSIONS Ascorbate content and the structure of the vitreous gel are critical determinants of lens oxygen exposure. Minimally invasive surgery and restoration of vitreous structure warrant further attention as strategies for preventing nuclear cataracts.
Collapse
Affiliation(s)
- Benjamen A Filas
- Department of Ophthalmology & Visual Sciences, Washington University School of Medicine, St. Louis, Missouri
| | | | | |
Collapse
|
20
|
Bonfiglio A, Repetto R, Siggers JH, Stocchino A. Investigation of the motion of a viscous fluid in the vitreous cavity induced by eye rotations and implications for drug delivery. Phys Med Biol 2013; 58:1969-82. [DOI: 10.1088/0031-9155/58/6/1969] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|