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Schumacher J, Lopez RR, Larin K, Manns F, Scarcelli G. Functional effects of the spatial-varying lens mechanical properties in accommodation. JPHYS PHOTONICS 2024; 6:035021. [PMID: 38975030 PMCID: PMC11223182 DOI: 10.1088/2515-7647/ad3e55] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 03/25/2024] [Accepted: 04/12/2024] [Indexed: 07/09/2024] Open
Abstract
Lens biomechanical properties are critical for our eyes to accommodate. While it is well understood that lens mechanical properties change with age, different experimental techniques have been used over the years, with varying results on how the lens modulus changes. In this study, we developed a spatial-varying elasticity model to characterize the overall elastic modulus of the lens and establish its effect on accommodation. First, to validate the model, ex vivo porcine lenses underwent compression testing using biopsy punches of different diameters to change the percentage of nucleus within samples. Importantly, we found that, indeed, changing nucleus/cortex spatial ratio produces dramatic (∼7-fold) increase in overall sample modulus. Comparing the model with human lens spatial ratios, we demonstrate how changing spatial mechanics are more influential than peak modulus changes on overall elastic modulus. Next, in vivo clinical measurements of the spatial-varying lens modulus were used to generate a simplified mechanical-optical model of accommodation. We defined an ellipsoid lens with patient-derived modulus and geometry measurements, and a statics simulation and ray tracing analysis were performed through the deformed and undeformed lens. The resulting accommodation estimates agree with general accommodation expectations.
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Affiliation(s)
- Justin Schumacher
- Fischell Department of Bioengineering, University of Maryland, College Park, United States of America
| | - Raymundo Rodriguez Lopez
- Fischell Department of Bioengineering, University of Maryland, College Park, United States of America
| | - Kirill Larin
- Department of Biomedical Engineering, University of Houston, Houston, TX, United States of America
| | - Fabrice Manns
- Department of Biomedical Engineering, University of Miami, Coral Gables, FL, United States of America
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, United States of America
| | - Giuliano Scarcelli
- Fischell Department of Bioengineering, University of Maryland, College Park, United States of America
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2
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Design of an Automatically Controlled Multi-Axis Stretching Device for Mechanical Evaluations of the Anterior Eye Segment. Bioengineering (Basel) 2023; 10:bioengineering10020142. [PMID: 36829636 PMCID: PMC9952546 DOI: 10.3390/bioengineering10020142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 01/14/2023] [Accepted: 01/18/2023] [Indexed: 01/22/2023] Open
Abstract
The young eye has an accommodative ability involving lens shape changes to focus over different distances. This function gradually decreases with age, resulting in presbyopia. Greater insights into the mechanical properties of anterior eye structures can improve understanding of the causes of presbyopia. The present study aims to develop a multi-axis stretching device for evaluating the mechanical properties of the intact eye lens. A stretching device integrating the mechanical stretcher, motor, torque sensor and data transmission mechanism was designed and developed by 3D printing. The mechanical stretcher can convert rotation into radial movement, both at constant speeds, according to the spiral of Archimedes. The loading unit equipped with eight jaws can hold the eye sample tightly. The developed device was validated with a spring of known constant and was further tested with anterior porcine eye segments. The validation experiment using the spring resulted in stiffness values close to the theoretical spring constant. Findings from measurements with porcine eye samples indicated that the measured forces are within the ranges reported in the literature. The developed multi-axis stretching device has good repeatability during experiments with similar settings and can be reliably used for mechanical evaluations of the intact eye lens.
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3
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The Imaging Characteristics of Lens Subluxation on the Ultrasound Biomicroscopy. CONTRAST MEDIA & MOLECULAR IMAGING 2022; 2022:7030866. [PMID: 36051917 PMCID: PMC9420649 DOI: 10.1155/2022/7030866] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Revised: 07/14/2022] [Accepted: 07/29/2022] [Indexed: 11/29/2022]
Abstract
Background To evaluate the imaging characteristics of the lens subluxation with the use of ultrasound biomicroscopy. Methods From October 2018 to September 2019, 55 eyes diagnosed with lens subluxation were enrolled in the group. All patients underwent detailed eye examination and panoramic ultrasound biomicroscopy. Results The most common sites of lens suspensory ligament injury were superior temporal side (32.73%) and superior nasal side (23.63%). The most common range of subluxation in all patients was 30°. Comparing the measurement indicators of all patients, ciliary body thickness (CBT) in affected eyes was smaller than that in healthy eyes (0.79 ± 0.21, 1.04 ± 0.16), the distance between ciliary process and crystal equator increased (1.91 ± 0.70, 1.17 ± 0.32), and iris-ciliary processes distance (ICPD) increased (1.04 ± 0.51, 0.80 ± 0.17) (P < 0.05). The range of subluxation in patients with lens subluxation was positively correlated with the distance between ciliary processes and the crystal equator. Conclusions The ultrasound biological microscope has a good application significance in the diagnosis of lens subluxation. From this study, we suggest that the three indexes of CBT, ICPD, and the distance between the ciliary process and crystal equator are of high reference value in ultrasound biomicroscopy among patients with lens subluxation.
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Rioboó RJJ, Gontán N, Sanderson D, Desco M, Gómez-Gaviro MV. Brillouin Spectroscopy: From Biomedical Research to New Generation Pathology Diagnosis. Int J Mol Sci 2021; 22:8055. [PMID: 34360822 PMCID: PMC8347166 DOI: 10.3390/ijms22158055] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Revised: 07/11/2021] [Accepted: 07/23/2021] [Indexed: 01/06/2023] Open
Abstract
Brillouin spectroscopy has recently gained considerable interest within the biomedical field as an innovative tool to study mechanical properties in biology. The Brillouin effect is based on the inelastic scattering of photons caused by their interaction with thermodynamically driven acoustic modes or phonons and it is highly dependent on the material's elasticity. Therefore, Brillouin is a contactless, label-free optic approach to elastic and viscoelastic analysis that has enabled unprecedented analysis of ex vivo and in vivo mechanical behavior of several tissues with a micrometric resolution, paving the way to a promising future in clinical diagnosis. Here, we comprehensively review the different studies of this fast-moving field that have been performed up to date to provide a quick guide of the current literature. In addition, we offer a general view of Brillouin's biomedical potential to encourage its further development to reach its implementation as a feasible, cost-effective pathology diagnostic tool.
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Affiliation(s)
- Rafael J. Jiménez Rioboó
- Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC), C/Sor Juana Inés de la Cruz, 3, 28049 Madrid, Spain;
| | - Nuria Gontán
- Instituto de Investigación Sanitaria Gregorio Marañón, 28007 Madrid, Spain; (N.G.); (D.S.)
- Departamento de Bioingeniería e Ingeniería Aeroespacial, Universidad Carlos III, 28911 Madrid, Spain
| | - Daniel Sanderson
- Instituto de Investigación Sanitaria Gregorio Marañón, 28007 Madrid, Spain; (N.G.); (D.S.)
- Departamento de Bioingeniería e Ingeniería Aeroespacial, Universidad Carlos III, 28911 Madrid, Spain
| | - Manuel Desco
- Instituto de Investigación Sanitaria Gregorio Marañón, 28007 Madrid, Spain; (N.G.); (D.S.)
- Departamento de Bioingeniería e Ingeniería Aeroespacial, Universidad Carlos III, 28911 Madrid, Spain
- Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), 28029 Madrid, Spain
- Centro Nacional de Investigaciones Cardiovasculares Carlos III, 28029 Madrid, Spain
| | - Maria Victoria Gómez-Gaviro
- Instituto de Investigación Sanitaria Gregorio Marañón, 28007 Madrid, Spain; (N.G.); (D.S.)
- Departamento de Bioingeniería e Ingeniería Aeroespacial, Universidad Carlos III, 28911 Madrid, Spain
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In vivo ultraosound elastographic evaluation of the age-related change of human lens nuclear stiffness. BMC Ophthalmol 2020; 20:135. [PMID: 32252697 PMCID: PMC7137519 DOI: 10.1186/s12886-020-01404-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2019] [Accepted: 03/25/2020] [Indexed: 11/26/2022] Open
Abstract
Background To evaluate the age-related changes in the stiffness of the human lens nucleus in vivo. Methods A total of 78 volunteers with best-corrected visual acuity of 20/20with a mean ± standard deviation intraocular pressure (IOP) of 16 ± 2.5 mmHg were divided into 3 groups of 26. The mean ages of Groups A, B and C were 81 ± 5.5, 44 ± 3.2 and 21 ± 2.5 years, with mean axial lengths of 23.8 ± 0.5 mm, 23.8 ± 0.4 mm and 23.9 ± 0.3 mm, respectively. Using an elastographer, the ultrasound echolucency and elastic strain rate of the lens nucleus of one eye, selected randomly, of each subject were measured three times. The strain rate of the lens cortex could not be assessed. The qualitative differences in the strain rates across the groups were assessed, and differences in the strain rate ratios of the lens nuclei across groups were analysed by one-way ANOVA. Results The strain rates of the lens nuclei of Group A were much lower than those in Groups B and C, as assessed qualitatively; the elastograph images of the lens nuclei of the older group showed a blue colour.The strain rate ratios of the lens nuclei of Groups A, B and C were 0.02 ± 0.08, 0.69 ± 0.12 and 1.95 ± 0.85, respectively. The differences in the lens nucleus strain rate ratios across the groups were statistically significant, with p-values < 0.05. Conclusions Ultrasound elastography demonstrated in vivo that an older age is associated with a statistically significantly lower lens nucleus strain rate ratio and therefore a markedly higher lens nuclear stiffness.
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6
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Refractive index redistribution with accommodation based on finite volume-constant age-dependent mechanical modeling. Vision Res 2020; 168:29-30. [DOI: 10.1016/j.visres.2019.08.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 07/15/2019] [Accepted: 08/21/2019] [Indexed: 11/22/2022]
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Jiang MS, Xu XL, Yang T, Zhang XD, Li F. Reply to comment by Ronald A. Schachar on the publication "Refractive index redistribution with accommodation based on finite volume-constant age-dependent mechanical modeling". Vision Res 2020; 168:31-32. [PMID: 32062175 DOI: 10.1016/j.visres.2020.01.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 01/01/2020] [Accepted: 01/02/2020] [Indexed: 11/25/2022]
Affiliation(s)
- Min-Shan Jiang
- Engineering Research Center of Optical Instruments and Systems, Ministry of Education, Shanghai Key Lab of Modern Optical Systems, University of Shanghai for Science and Technology, Shanghai, China
| | - Xiao-Li Xu
- Engineering Research Center of Optical Instruments and Systems, Ministry of Education, Shanghai Key Lab of Modern Optical Systems, University of Shanghai for Science and Technology, Shanghai, China
| | - Ting Yang
- Engineering Research Center of Optical Instruments and Systems, Ministry of Education, Shanghai Key Lab of Modern Optical Systems, University of Shanghai for Science and Technology, Shanghai, China
| | - Xue-Dian Zhang
- Engineering Research Center of Optical Instruments and Systems, Ministry of Education, Shanghai Key Lab of Modern Optical Systems, University of Shanghai for Science and Technology, Shanghai, China
| | - Feng Li
- Engineering Research Center of Optical Instruments and Systems, Ministry of Education, Shanghai Key Lab of Modern Optical Systems, University of Shanghai for Science and Technology, Shanghai, China.
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Wang K, Venetsanos DT, Hoshino M, Uesugi K, Yagi N, Pierscionek BK. A Modeling Approach for Investigating Opto-Mechanical Relationships in the Human Eye Lens. IEEE Trans Biomed Eng 2019; 67:999-1006. [PMID: 31395531 DOI: 10.1109/tbme.2019.2927390] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECTIVE The human visual system alters its focus by a shape change of the eye lens. The extent to which the lens can adjust ocular refractive power is dependent to a significant extent on its material properties. Yet, this fundamental link between the optics and mechanics of the lens has been relatively under-investigated. This study aims to investigate this opto-mechanical link within the eye lens to gain insight into the processes of shape alteration and their respective decline with age. METHODS Finite Element models based on biological lenses were developed for five ages: 16, 35, 40, 57, and 62 years by correlating in vivo measurements of the longitudinal modulus using Brillouin scattering with in vitro X-ray interferometric measurements of refractive index and taking into account various directions of zonular force. RESULTS A model with radial cortical Young's moduli provides the same amount of refractive power with less change in thickness than a model with uniform cortical Young's modulus with a uniform stress distribution and no discontinuities along the cortico-nuclear boundary. The direction of zonular angles can significantly influence curvature change regardless of the modulus distribution. CONCLUSIONS The present paper proposes a modelling approach for the human lens, coupling optical and mechanical properties, which shows the effect of parameter choice on model response. SIGNIFICANCE This advanced modelling approach, considering the important interplay between optical and mechanical properties, has potential for use in design of accommodating implant lenses and for investigating non-biological causes of pathological processes in the lens (e.g., cataract).
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WANG KEHAO, VENETSANOS DEMETRIOST, WANG JIAN, PIERSCIONEK BARBARAK. COMBINED USE OF PARALLEL-PLATE COMPRESSION AND FINITE ELEMENT MODELING TO ANALYZE THE MECHANICAL PROPERTIES OF INTACT PORCINE LENS. J MECH MED BIOL 2018. [DOI: 10.1142/s0219519418400134] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The objective of this study is to explore the feasibility of a compression test for measuring mechanical properties of intact eye lenses using novel parallel plate compression equipment to compare the accuracy of implementing a classical Hertzian model and a newly proposed adjusted Hertzian model to calculate Young’s modulus from compression test results using finite element (FE) analysis. Parallel-plate compression tests were performed on porcine lenses. An axisymmetric FE model was developed to simulate the experimental process to evaluate the accuracy of using the classical Hertzian theory of contact mechanics as well as a newly proposed adjusted Hertzian theory model for calculating the equivalent Young’s modulus. By fitting the force-displacement relation obtained from FE simulations to both the classical and adjusted Hertzian theory model and comparing the calculated modulus to the input modulus of the FE model, the results demonstrated that the classical Hertzian theory model overestimated the Young’s modulus with a proportional error of over 10%. The adjusted Hertzian theory model produced results that are closer to original input values with error ratios all lower than 1.29%. Measurements of three porcine lenses from the parallel plate compression experiments were analyzed with resulting values of Young’s modulus of between 3.2[Formula: see text]kPa and 4.3[Formula: see text]kPa calculated. This study demonstrates that the adjusted Hertzian theory of contact mechanics can be applied in conjunction with the parallel-plate compression system to investigate the overall mechanical behavior of intact lenses.
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Affiliation(s)
- KEHAO WANG
- School of Science and Technology, Nottingham Trent University, Clifton Campus, Clifton Lane, Nottingham, NG11 8NS, UK
| | - DEMETRIOS T. VENETSANOS
- School of Mechanical, Aerospace and Automotive Engineering, Coventry University, Priory Street, Coventry, CV1 5FB, UK
| | - JIAN WANG
- Faculty of Science Engineering and Computing, Kingston University, Penrhyn Road, Kingston-Upon-Thames, KT1 2EE, UK
| | - BARBARA K. PIERSCIONEK
- School of Science and Technology, Nottingham Trent University, Clifton Campus, Clifton Lane, Nottingham, NG11 8NS, UK
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10
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Role of 25 MHz Ultrasound Biomicroscopy in the Detection of Subluxated Lenses. J Ophthalmol 2018; 2018:3760280. [PMID: 30416825 PMCID: PMC6207873 DOI: 10.1155/2018/3760280] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 07/13/2018] [Accepted: 08/01/2018] [Indexed: 11/18/2022] Open
Abstract
Background The purpose of this observational case series study was to investigate the role of 25 MHz ultrasound biomicroscopy (UBM) in detecting subluxated lenses and compare it with 50 MHz UBM. Methods 45 patients (49 eyes) with suspected subluxation of the lens and 20 normal volunteers (40 eyes) were included. Different cross-sectional images of the lens position were captured in axial and longitudinal scanning modes using 25 and 50 MHz UBM. The main outcome measurements included the linear distance between the lens equator and ciliary process, the difference value (D-value) between the same cross section of the above bilateral linear distance in the normal and the subluxated subjects, the diagnostic accuracy, and the testing times obtained with 25 and 50 MHz UBM. Results The position of the lens on axial sections could be clearly shown by using 25 MHz UBM. The D-value of the subluxated eyes was 1-2 mm longer than that of the normal ones. There was a statistically significant difference between 25 and 50 MHz UBM in showing subluxation of the lens, the testing time was significantly faster (2.0 min versus 7.5 min), and the diagnostic accuracy was much higher (98.0% versus 71.4%) with 25 versus 50 MHz UBM. Fifteen eyes with slightly subluxated lens were detected by 25 MHz UBM, and only one eye with slight lens subluxation was detected by 50 MHz UBM. Conclusions The results indicated that 25 MHz UBM has a greater diagnostic value than 50 MHz UBM in verifying the status of the lens subluxation and can provide reliable and quantitative imaging evidence for clinical use. This trial is registered with ChiCTR–DOD –15007603.
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11
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Parreno J, Cheng C, Nowak RB, Fowler VM. The effects of mechanical strain on mouse eye lens capsule and cellular microstructure. Mol Biol Cell 2018; 29:1963-1974. [PMID: 30088796 PMCID: PMC6232967 DOI: 10.1091/mbc.e18-01-0035] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The mouse eye lens was used as a model for multiscale transfer of loads. In the lens, compressive strain is distributed across specific lens tissue microstructures, including the extracellular capsule, as well as the epithelial and fiber cells. The removal of high loads resulted in complete recovery of most, but not all, microstructures. The understanding of multiscale load transfer within complex soft tissues is incomplete. The eye lens is ideal for multiscale mechanical studies because its principal function is to fine-focus light at different distances onto the retina via shape changes. The biomechanical function, resiliency, and intricate microstructure of the lens makes it an excellent nonconnective soft tissue model. We hypothesized that strain applied onto whole-lens tissue leads to deformation of specific microstructures and that this deformation is reversible following load removal. For this examination, mouse lenses were compressed by sequential application of increasing load. Using confocal microscopy and quantitative image analysis, we determined that axial strain ≥10% reduces capsule thickness, expands epithelial cell area, and separates fiber cell tips at the anterior region. At the equatorial region, strain ≥6% increases fiber cell widths. The effects of strain on lens epithelial cell area, capsule thickness, and fiber cell widths are reversible following the release from strain. However, the separation of fiber cell tips is irreversible at high loads. This irreversible separation between fiber cell tips leads to incomplete whole-lens resiliency. The lens is an accessible biomechanical model system that provides new insights on multiscale transfer of loads in soft tissues.
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Affiliation(s)
- Justin Parreno
- Department of Molecular Medicine, Scripps Research Institute, La Jolla, CA 92037
| | - Catherine Cheng
- Department of Molecular Medicine, Scripps Research Institute, La Jolla, CA 92037
| | - Roberta B Nowak
- Department of Molecular Medicine, Scripps Research Institute, La Jolla, CA 92037
| | - Velia M Fowler
- Department of Molecular Medicine, Scripps Research Institute, La Jolla, CA 92037
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12
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The importance of parameter choice in modelling dynamics of the eye lens. Sci Rep 2017; 7:16688. [PMID: 29192148 PMCID: PMC5709469 DOI: 10.1038/s41598-017-16854-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Accepted: 11/18/2017] [Indexed: 11/08/2022] Open
Abstract
The lens provides refractive power to the eye and is capable of altering ocular focus in response to visual demand. This capacity diminishes with age. Current biomedical technologies, which seek to design an implant lens capable of replicating the function of the biological lens, are unable as yet to provide such an implant with the requisite optical quality or ability to change the focussing power of the eye. This is because the mechanism of altering focus, termed accommodation, is not fully understood and seemingly conflicting theories require experimental support which is difficult to obtain from the living eye. This investigation presents finite element models of the eye lens based on data from human lenses aged 16 and 35 years that consider the influence of various modelling parameters, including material properties, a wide range of angles of force application and capsular thickness. Results from axisymmetric models show that the anterior and posterior zonules may have a greater impact on shape change than the equatorial zonule and that choice of capsular thickness values can influence the results from modelled simulations.
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13
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Besner S, Scarcelli G, Pineda R, Yun SH. In Vivo Brillouin Analysis of the Aging Crystalline Lens. Invest Ophthalmol Vis Sci 2017; 57:5093-5100. [PMID: 27699407 PMCID: PMC5054731 DOI: 10.1167/iovs.16-20143] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Purpose To analyze the age dependence of the longitudinal modulus of the crystalline lens in vivo using Brillouin scattering data in healthy subjects. Methods Brillouin scans were performed along the crystalline lens in 56 eyes from 30 healthy subjects aged from 19 to 63 years. Longitudinal elastic modulus was acquired along the sagittal axis of the lens with a transverse and axial resolution of 4 and 60 μm, respectively. The relative lens stiffness was computed, and correlations with age were analyzed. Results Brillouin axial profiles revealed nonuniform longitudinal modulus within the lens, increasing from a softer periphery toward a stiffer central plateau at all ages. The longitudinal modulus at the central plateau showed no age dependence in a range of 19 to 45 years and a slight decrease with age from 45 to 63 years. A significant intersubject variability was observed in an age-matched analysis. Importantly, the extent of the central stiff plateau region increased steadily over age from 19 to 63 years. The slope of change in Brillouin modulus in the peripheral regions were nearly age-invariant. Conclusions The adult human lens showed no measurable age-related increase in the peak longitudinal modulus. The expansion of the stiff central region of the lens is likely to be the major contributing factor to age-related lens stiffening. Brillouin microscopy may be useful in characterizing the crystalline lens for the optimization of surgical or pharmacological treatments aimed at restoring accommodative power.
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Affiliation(s)
- Sebastien Besner
- Wellman Center for Photomedicine, Massachusetts General Hospital, Cambridge, Massachusetts, United States 2Department of Dermatology, Harvard Medical School, Boston, Massachusetts, United States
| | - Giuliano Scarcelli
- Wellman Center for Photomedicine, Massachusetts General Hospital, Cambridge, Massachusetts, United States 2Department of Dermatology, Harvard Medical School, Boston, Massachusetts, United States 3Fischell Department of Bioengineering, University of Maryland, College Park, Maryland, United States
| | - Roberto Pineda
- Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, United States
| | - Seok-Hyun Yun
- Wellman Center for Photomedicine, Massachusetts General Hospital, Cambridge, Massachusetts, United States 2Department of Dermatology, Harvard Medical School, Boston, Massachusetts, United States 5Harvard-MIT Health Sciences and Technology, Cambridge, Massachusetts, United States
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14
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Line-scanning Brillouin microscopy for rapid non-invasive mechanical imaging. Sci Rep 2016; 6:35398. [PMID: 27739499 PMCID: PMC5064313 DOI: 10.1038/srep35398] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 09/28/2016] [Indexed: 11/09/2022] Open
Abstract
Brillouin spectroscopy probes the mechanical properties of material by measuring the optical frequency shift induced by photon-phonon scattering interactions. In traditional configurations, Brillouin spectrometers measure only one point of the sample at a time. This results in long acquisition times for mechanical imaging of large areas. In this work, we demonstrate a parallel detection configuration where the Brillouin shift of hundreds of points in a line can be measured simultaneously. In mm-sized samples, this novel configuration effectively shortens the acquisition time of two-dimensional Brillouin imaging from hours to tens of seconds, thus making it a powerful technology for label-free mechanical characterization of tissue and biomaterials.
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15
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Wang K, Venetsanos D, Wang J, Pierscionek BK. Gradient moduli lens models: how material properties and application of forces can affect deformation and distributions of stress. Sci Rep 2016; 6:31171. [PMID: 27507665 PMCID: PMC4979009 DOI: 10.1038/srep31171] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 07/13/2016] [Indexed: 11/11/2022] Open
Abstract
The human lens provides one-third of the ocular focussing power and is responsible for altering focus over a range of distances. This ability, termed accommodation, defines the process by which the lens alters shape to increase or decrease ocular refractive power; this is mediated by the ciliary muscle through the zonule. This ability decreases with age such that around the sixth decade of life it is lost rendering the eye unable to focus on near objects. There are two opponent theories that provide an explanation for the mechanism of accommodation; definitive support for either of these requires investigation. This work aims to elucidate how material properties can affect accommodation using Finite Element models based on interferometric measurements of refractive index. Gradients of moduli are created in three models from representative lenses, aged 16, 35 and 48 years. Different forms of zonular attachments are studied to determine which may most closely mimic the physiological form by comparing stress and displacement fields with simulated shape changes to accommodation in living lenses. The results indicate that for models to mimic accommodation in living eyes, the anterior and posterior parts of the zonule need independent force directions. Choice of material properties affects which theory of accommodation is supported.
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Affiliation(s)
- Kehao Wang
- Faculty of Science Engineering and Computing, Penrhyn Road, KT1 2EE, Kingston-upon-Thames, UK
| | - Demetrios Venetsanos
- Faculty of Science Engineering and Computing, Penrhyn Road, KT1 2EE, Kingston-upon-Thames, UK
| | - Jian Wang
- Faculty of Science Engineering and Computing, Penrhyn Road, KT1 2EE, Kingston-upon-Thames, UK
| | - Barbara K Pierscionek
- Faculty of Science Engineering and Computing, Penrhyn Road, KT1 2EE, Kingston-upon-Thames, UK
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Mahjoob M, Heydarian S, Koochi S. Effect of yellow filter on visual acuity and contrast sensitivity under glare condition among different age groups. Int Ophthalmol 2015; 36:509-14. [DOI: 10.1007/s10792-015-0154-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2015] [Accepted: 11/24/2015] [Indexed: 11/29/2022]
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17
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Wu C, Han Z, Wang S, Li J, Singh M, Liu CH, Aglyamov S, Emelianov S, Manns F, Larin KV. Assessing age-related changes in the biomechanical properties of rabbit lens using a coaligned ultrasound and optical coherence elastography system. Invest Ophthalmol Vis Sci 2015; 56:1292-300. [PMID: 25613945 DOI: 10.1167/iovs.14-15654] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
PURPOSE To evaluate the capability of a novel, coaligned focused ultrasound and phase-sensitive optical coherence elastography (US-OCE) system to assess age-related changes in biomechanical properties of the crystalline lens in situ. METHODS Low-amplitude elastic deformations in young and mature rabbit lenses were measured by an US-OCE system consisting of a spectral-domain optical coherence tomography (OCT) system coaligned with a focused ultrasound system used to produce a transient force on the lens surface. Uniaxial compressional tests were used to validate the OCE data. RESULTS The OCE measurements showed that the maximum displacements of the young rabbit lenses were significantly larger than those of the mature lenses, indicating a gradual increase of the lens stiffness with age. Temporal analyses of the displacements also demonstrate a similar trend of elastic properties in these lenses. The stress-strain measurements using uniaxial mechanical tests confirmed the results obtained by the US-OCE system. CONCLUSIONS The results demonstrate that the US-OCE system can be used for noninvasive analysis and quantification of lens biomechanical properties in situ and possibly in vivo.
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Affiliation(s)
- Chen Wu
- Department of Biomedical Engineering, University of Houston, Houston, Texas, United States
| | - Zhaolong Han
- Department of Biomedical Engineering, University of Houston, Houston, Texas, United States
| | - Shang Wang
- Department of Biomedical Engineering, University of Houston, Houston, Texas, United States Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas, United States
| | - Jiasong Li
- Department of Biomedical Engineering, University of Houston, Houston, Texas, United States
| | - Manmohan Singh
- Department of Biomedical Engineering, University of Houston, Houston, Texas, United States
| | - Chih-Hao Liu
- Department of Biomedical Engineering, University of Houston, Houston, Texas, United States
| | - Salavat Aglyamov
- Department of Biomedical Engineering, University of Texas at Austin, Austin, Texas, United States
| | - Stanislav Emelianov
- Department of Biomedical Engineering, University of Texas at Austin, Austin, Texas, United States
| | - Fabrice Manns
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States Biomedical Optics and Laser Laboratory, Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, Florida, United States
| | - Kirill V Larin
- Department of Biomedical Engineering, University of Houston, Houston, Texas, United States Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas, United States
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Girard MJA, Dupps WJ, Baskaran M, Scarcelli G, Yun SH, Quigley HA, Sigal IA, Strouthidis NG. Translating ocular biomechanics into clinical practice: current state and future prospects. Curr Eye Res 2015; 40:1-18. [PMID: 24832392 PMCID: PMC4233020 DOI: 10.3109/02713683.2014.914543] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Biomechanics is the study of the relationship between forces and function in living organisms and is thought to play a critical role in a significant number of ophthalmic disorders. This is not surprising, as the eye is a pressure vessel that requires a delicate balance of forces to maintain its homeostasis. Over the past few decades, basic science research in ophthalmology mostly confirmed that ocular biomechanics could explain in part the mechanisms involved in almost all major ophthalmic disorders such as optic nerve head neuropathies, angle closure, ametropia, presbyopia, cataract, corneal pathologies, retinal detachment and macular degeneration. Translational biomechanics in ophthalmology, however, is still in its infancy. It is believed that its use could make significant advances in diagnosis and treatment. Several translational biomechanics strategies are already emerging, such as corneal stiffening for the treatment of keratoconus, and more are likely to follow. This review aims to cultivate the idea that biomechanics plays a major role in ophthalmology and that the clinical translation, lead by collaborative teams of clinicians and biomedical engineers, will benefit our patients. Specifically, recent advances and future prospects in corneal, iris, trabecular meshwork, crystalline lens, scleral and lamina cribrosa biomechanics are discussed.
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Affiliation(s)
- Michaël J A Girard
- In Vivo Biomechanics Laboratory, Department of Biomedical Engineering, National University of Singapore , Singapore
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Yoon S, Aglyamov S, Karpiouk A, Emelianov S. The mechanical properties of ex vivo bovine and porcine crystalline lenses: age-related changes and location-dependent variations. ULTRASOUND IN MEDICINE & BIOLOGY 2013; 39:1120-7. [PMID: 23453376 PMCID: PMC3646975 DOI: 10.1016/j.ultrasmedbio.2012.12.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Revised: 11/01/2012] [Accepted: 12/15/2012] [Indexed: 05/03/2023]
Abstract
The mechanical properties of ex vivo animal lenses from three groups were evaluated: old bovine (25-30 mo old, n = 4), young bovine (6 mo old, n = 4) and young porcine (6 mo old, n = 4) eye globes. We measured the dynamics of laser-induced microbubbles created at different locations within the crystalline lenses. An impulsive acoustic radiation force was applied to the microbubble, and the microbubble displacements were measured using a custom-built high pulse repetition frequency ultrasound system. Based on the measured dynamics of the microbubbles, Young's moduli of bovine and porcine lens tissue in the vicinity of the microbubbles were reconstructed. Age-related changes and location-dependent variations in the Young's modulus of the lenses were observed. Near the center, the old bovine lenses had a Young's modulus approximately fivefold higher than that of young bovine and porcine lenses. The gradient of Young's modulus with respect to radial distance was observed in the lenses from three groups.
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Affiliation(s)
- Sangpil Yoon
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712
- Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX 78712
| | - Salavat Aglyamov
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712
| | - Andrei Karpiouk
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712
| | - Stanislav Emelianov
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712
- Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX 78712
- Corresponding Author: 107 W. Dean Keeton St. Austin, TX 78712; ; +1-512-471-1733
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20
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Wang S, Aglyamov S, Karpiouk A, Li J, Emelianov S, Manns F, Larin KV. Assessing the mechanical properties of tissue-mimicking phantoms at different depths as an approach to measure biomechanical gradient of crystalline lens. BIOMEDICAL OPTICS EXPRESS 2013; 4:2769-80. [PMID: 24409379 PMCID: PMC3862146 DOI: 10.1364/boe.4.002769] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 11/05/2013] [Accepted: 11/06/2013] [Indexed: 05/12/2023]
Abstract
We demonstrate the feasibility of using the dominant frequency of the sample surface response to a mechanical stimulation as an effective indicator for sensing the depthwise distribution of elastic properties in transparent layered phantom samples simulating the cortex and nucleus of the crystalline lens. Focused ultrasound waves are used to noninvasively interrogate the sample surface. A phase-sensitive optical coherence tomography system is utilized to capture the surface dynamics over time with nanometer scale sensitivity. Spectral analysis is performed on the sample surface response to ultrasound stimulation and the dominant frequency is calculated under particular loading parameters. Pilot experiments were conducted on homogeneous and layered tissue-mimicking phantoms. Results indicate that the mechanical layers located at different depths introduce different frequencies to the sample surface response, which are correlated with the depth-dependent elasticity of the sample. The duration and the frequency of the ultrasound excitation are also investigated for their influences on this spectrum-based detection. This noninvasive method may be potentially applied for localized and rapid assessment of the depth dependence of the mechanical properties of the crystalline lens.
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Affiliation(s)
- Shang Wang
- Department of Biomedical Engineering, University of Houston, 3605 Cullen Boulevard, Houston, Texas 77204, USA
| | - Salavat Aglyamov
- Department of Biomedical Engineering, The University of Texas at Austin, 107 W Dean Keeton Street, Austin, Texas 78712, USA
| | - Andrei Karpiouk
- Department of Biomedical Engineering, The University of Texas at Austin, 107 W Dean Keeton Street, Austin, Texas 78712, USA
| | - Jiasong Li
- Department of Biomedical Engineering, University of Houston, 3605 Cullen Boulevard, Houston, Texas 77204, USA
| | - Stanislav Emelianov
- Department of Biomedical Engineering, The University of Texas at Austin, 107 W Dean Keeton Street, Austin, Texas 78712, USA
| | - Fabrice Manns
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, 1638 NW 10th Avenue, Miami, Florida 33136, USA
- Biomedical Optics and Laser Laboratory, Department of Biomedical Engineering, University of Miami College of Engineering, 1251 Memorial Drive, Coral Gables, Florida 33146, USA
| | - Kirill V. Larin
- Department of Biomedical Engineering, University of Houston, 3605 Cullen Boulevard, Houston, Texas 77204, USA
- Molecular Physiology and Biophysics, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77584, USA
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21
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Reiss S, Sperlich K, Hovakimyan M, Martius P, Guthoff RF, Stolz H, Stachs O. Ex vivo measurement of postmortem tissue changes in the crystalline lens by Brillouin spectroscopy and confocal reflectance microscopy. IEEE Trans Biomed Eng 2012; 59:2348-54. [PMID: 22711764 DOI: 10.1109/tbme.2012.2204054] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Use of Brillouin spectroscopy in ophthalmology enables noninvasive, spatially resolved determination of the rheological properties of crystalline lens tissue. Furthermore, the Brillouin shift correlates with the protein concentration inside the lens. In vitro measurements on extracted porcine lenses demonstrate that results obtained with Brillouin spectroscopy depend strongly on time after death. The intensity of the Brillouin signal decreases significantly as early as 5 h postmortem. Moreover, the fluctuation of the Brillouin frequency shift inside the lens increases with postmortem time. Images of lens tissue taken with a confocal reflectance microscope between measurements reveal a degenerative aging process. These tissue changes correlate with our results from Brillouin spectroscopy. It is concluded that only in vivo measurements appropriately reflect the rheological properties of the eye lens and its protein concentration.
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Affiliation(s)
- Stephan Reiss
- Institute for Physics, University of Rostock, Rostock, Germany.
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22
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Scarcelli G, Yun SH. In vivo Brillouin optical microscopy of the human eye. OPTICS EXPRESS 2012; 20:9197-202. [PMID: 22513631 PMCID: PMC3500092 DOI: 10.1364/oe.20.009197] [Citation(s) in RCA: 113] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Revised: 03/30/2012] [Accepted: 04/01/2012] [Indexed: 05/18/2023]
Abstract
We report the first Brillouin measurement of the human eye in vivo. We constructed a Brillouin optical scanner safe for human use by employing continuous-wave laser light at 780 nm at a low power of 0.7 mW. With a single scan along the optic axis of the eye, the axial profile of Brillouin frequency shift was obtained with a pixel acquisition time of 0.4 s and axial resolution of about 60 μm, showing the depth-dependent biomechanical properties in the cornea and lens.
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23
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In vivo measurement of age-related stiffening in the crystalline lens by Brillouin optical microscopy. Biophys J 2011; 101:1539-45. [PMID: 21943436 DOI: 10.1016/j.bpj.2011.08.008] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Revised: 07/06/2011] [Accepted: 08/03/2011] [Indexed: 11/22/2022] Open
Abstract
The biophysical and biomechanical properties of the crystalline lens (e.g., viscoelasticity) have long been implicated in accommodation and vision problems, such as presbyopia and cataracts. However, it has been difficult to measure such parameters noninvasively. Here, we used in vivo Brillouin optical microscopy to characterize material acoustic properties at GHz frequency and measure the longitudinal elastic moduli of lenses. We obtained three-dimensional elasticity maps of the lenses in live mice, which showed biomechanical heterogeneity in the cortex and nucleus of the lens with high spatial resolution. An in vivo longitudinal study of mice over a period of 2 months revealed a marked age-related stiffening of the lens nucleus. We found remarkably good correlation (log-log linear) between the Brillouin elastic modulus and the Young's modulus measured by conventional mechanical techniques at low frequencies (~1 Hz). Our results suggest that Brillouin microscopy is potentially useful for basic and animal research and clinical ophthalmology.
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Reiß S, Burau G, Stachs O, Guthoff R, Stolz H. Spatially resolved Brillouin spectroscopy to determine the rheological properties of the eye lens. BIOMEDICAL OPTICS EXPRESS 2011; 2:2144-59. [PMID: 21833354 PMCID: PMC3149515 DOI: 10.1364/boe.2.002144] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2011] [Revised: 06/29/2011] [Accepted: 07/02/2011] [Indexed: 05/04/2023]
Abstract
Presbyopia is closely associated with the loss of accommodation, and hence with a decline in the viscoelastic properties of the human eye lens. In this article we describe a method for obtaining spatially resolved in vivo measurements of the rheological properties of the eye lens, based on the spectroscopic analysis of spontaneous Brillouin scattering using a virtually imaged phased array (VIPA). The multi-pass configuration enhances resolution to the extent that measurements are possible in elastic biological tissue characterized by intense scattering. We also present spatially resolved measurements obtained in extracted animal eyes and lenses. The results yield entirely new insights into the aging process of the eye lens.
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Affiliation(s)
- Stephan Reiß
- Institute for Physics, Semiconductor Optics Group, University of Rostock, D-18055 Rostock, Germany
- Faculty of Medicine, Ophthalmology Clinic, University of Rostock, D-18055 Rostock, Germany
| | - Gerolf Burau
- Institute for Physics, Semiconductor Optics Group, University of Rostock, D-18055 Rostock, Germany
| | - Oliver Stachs
- Faculty of Medicine, Ophthalmology Clinic, University of Rostock, D-18055 Rostock, Germany
| | - Rudolf Guthoff
- Faculty of Medicine, Ophthalmology Clinic, University of Rostock, D-18055 Rostock, Germany
| | - Heinrich Stolz
- Institute for Physics, Semiconductor Optics Group, University of Rostock, D-18055 Rostock, Germany
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25
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Schachar RA. Finite element analysis and the Schachar mechanism of accommodation. J Cataract Refract Surg 2011; 37:979. [PMID: 21511174 DOI: 10.1016/j.jcrs.2011.03.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2011] [Indexed: 11/19/2022]
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26
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Leone G, Consumi M, Greco G, Bonechi C, Lamponi S, Rossi C, Magnani A. A PVA/PVP hydrogel for human lens substitution: Synthesis, rheological characterization, and in vitro biocompatibility. J Biomed Mater Res B Appl Biomater 2011; 97:278-88. [DOI: 10.1002/jbm.b.31813] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2010] [Revised: 10/26/2010] [Accepted: 12/14/2010] [Indexed: 11/12/2022]
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