Corneal biomechanical response following collagen cross-linking with Rose Bengal-green light and riboflavin-UVA

10 págs.; 9 figs. ; Open Access funded by Creative Commons Atribution Licence 4.0To compare the biomechanical corneal response of two different corneal cross-linking (CXL) treatments, rose bengal¿green light (RGX) and riboflavin-UVA (UVX), using noninvasive imaging.Supported by the European Research Council under the European Union’s Seventh Framework Program ERC Advanced Grant agreement no. 294099; Comunidad de Madrid and EU Marie Curie COFUND program (FP7/2007-2013/REA 291820); and the Spanish Government Grant FIS2014-56643-R.Peer Reviewe

Material properties from air puff corneal deformation by numerical simulations on model corneas

19 págs.; 11 figs.; 2 tabs.Objective To validate a new method for reconstructing corneal biomechanical properties from air puff corneal deformation images using hydrogel polymer model corneas and porcine corneas. Methods Air puff deformation imaging was performed on model eyes with artificial corneas made out of three different hydrogel materials with three different thicknesses and on porcine eyes, at constant intraocular pressure of 15 mmHg. The cornea air puff deformation was modeled using finite elements, and hyperelastic material parameters were determined through inverse modeling, minimizing the difference between the simulated and the measured central deformation amplitude and central-peripheral deformation ratio parameters. Uniaxial tensile tests were performed on the model cornea materials as well as on corneal strips, and the results were compared to stress-strain simulations assuming the reconstructed material parameters. Results The measured and simulated spatial and temporal profiles of the air puff deformation tests were in good agreement (< 7% average discrepancy). The simulated stress-strain curves of the studied hydrogel corneal materials fitted well the experimental stress-strain curves from uniaxial extensiometry, particularly in the 0-0.4 range. Equivalent Young?s moduli of the reconstructed material properties from air-puff were 0.31, 0.58 and 0.48 MPa for the three polymer materials respectively which differed < 1% from those obtained from extensiometry. The simulations of the same material but different thickness resulted in similar reconstructed material properties. The air-puff reconstructed average equivalent Young?s modulus of the porcine corneas was 1.3 MPa, within 18% of that obtained from extensiometry. Conclusions Air puff corneal deformation imaging with inverse finite element modeling can retrieve material properties of model hydrogel polymer corneas and real corneas, which are in good correspondence with those obtained from uniaxial extensiometry, suggesting that this is a promising technique to retrieve quantitative corneal biomechanical properties.This work was supported by the European Research Council under the European Union’s Seventh Framework Program ERC Advanced Grant agreement no. 294099 (erc.europa.eu) to SM; Comunidad de Madrid and EU Marie Curie COFUND program (FP7) 291820 (mvisionconsortium.org/) to NB; Ministerio de Economia y Competitividad Grant FIS2014-56643-R (www.mineco.gob.es) to SM; Ministerio de Economia y Competitividad Grant FIS2013-49544-EXP (www.mineco.gob.es) to CD; Ministerio de Economia y Competitividad FPI Fellowship BES-2015-072197 (www.idi.mineco.gob.es) to AdlH.Peer Reviewe

Numerical model of optical coherence tomographic vibrography imaging to estimate corneal biomechanical properties

Most techniques measuring corneal biomechanics in vivo are biased by side factors. We demonstrate the ability of optical coherence tomographic (OCT) vibrography to determine corneal material parameters, while reducing current prevalent restrictions of other techniques (such as intraocular pressure (IOP) and thickness dependency). Modal analysis was performed in a finite-element (FE) model to study the oscillation response in isolated thin corneal flaps/eye globes and to analyse the dependency of the frequency response function on: corneal elasticity, viscoelasticity, geometry (thickness and curvature), IOP and density. The model was verified experimentally in flaps from three bovine corneas and in two enucleated porcine eyes using sound excitation (100–110 dB) together with a phase-sensitive OCT to measure the frequency response function (range 50–510 Hz). Simulations showed that corneal vibration in flaps is sensitive to both, geometrical and biomechanical parameters, whereas in whole globes it is primarily sensitive to corneal biomechanical parameters only. Calculations based on the natural frequency shift revealed that flaps of the posterior cornea were 0.8 times less stiff than flaps from the anterior cornea and cross-linked corneas were 1.6 times stiffer than virgin corneas. Sensitivity analysis showed that natural vibration frequencies of whole globes were nearly independent from corneal thickness and IOP within the physiological range. OCT vibrography is a promising non-invasive technique to measure corneal elasticity without biases from corneal thickness and IOP

Material properties from air puff corneal deformation by numerical simulations on model corneas

19 págs.; 11 figs.; 2 tabs.Objective To validate a new method for reconstructing corneal biomechanical properties from air puff corneal deformation images using hydrogel polymer model corneas and porcine corneas. Methods Air puff deformation imaging was performed on model eyes with artificial corneas made out of three different hydrogel materials with three different thicknesses and on porcine eyes, at constant intraocular pressure of 15 mmHg. The cornea air puff deformation was modeled using finite elements, and hyperelastic material parameters were determined through inverse modeling, minimizing the difference between the simulated and the measured central deformation amplitude and central-peripheral deformation ratio parameters. Uniaxial tensile tests were performed on the model cornea materials as well as on corneal strips, and the results were compared to stress-strain simulations assuming the reconstructed material parameters. Results The measured and simulated spatial and temporal profiles of the air puff deformation tests were in good agreement (< 7% average discrepancy). The simulated stress-strain curves of the studied hydrogel corneal materials fitted well the experimental stress-strain curves from uniaxial extensiometry, particularly in the 0-0.4 range. Equivalent Young?s moduli of the reconstructed material properties from air-puff were 0.31, 0.58 and 0.48 MPa for the three polymer materials respectively which differed < 1% from those obtained from extensiometry. The simulations of the same material but different thickness resulted in similar reconstructed material properties. The air-puff reconstructed average equivalent Young?s modulus of the porcine corneas was 1.3 MPa, within 18% of that obtained from extensiometry. Conclusions Air puff corneal deformation imaging with inverse finite element modeling can retrieve material properties of model hydrogel polymer corneas and real corneas, which are in good correspondence with those obtained from uniaxial extensiometry, suggesting that this is a promising technique to retrieve quantitative corneal biomechanical properties.This work was supported by the European Research Council under the European Union’s Seventh Framework Program ERC Advanced Grant agreement no. 294099 (erc.europa.eu) to SM; Comunidad de Madrid and EU Marie Curie COFUND program (FP7) 291820 (mvisionconsortium.org/) to NB; Ministerio de Economia y Competitividad Grant FIS2014-56643-R (www.mineco.gob.es) to SM; Ministerio de Economia y Competitividad Grant FIS2013-49544-EXP (www.mineco.gob.es) to CD; Ministerio de Economia y Competitividad FPI Fellowship BES-2015-072197 (www.idi.mineco.gob.es) to AdlH.Peer Reviewe

Biomechanical properties and IOP reconstruction from air-puff corneal deformation imaging: validations in model and porcine eyes

ARVO 2016 Annual Meeting is Research: A vision of hope, Seattle, WA, Sunday, May 1 - Thursday, May 5, 2016High speed imaging together with numerical optimization allows simultaneous accurate reconstruction of both corneal mechanical properties and IOP, as validated with models ex vivo. This study extends previous work where the reconstructed mechanical parameters were obtained ex vivo with fixed, known IOPComunidad de Madrid & EU Marie Curie (FP7/2007-2013/ REA 291820), ERC Advanced Grant 294099, Spanish Government Grant FIS2014-56643-RPeer Reviewe

Corneal viscoelastic properties from finite-element analysis of in vivo air-puff deformation

Biomechanical properties are an excellent health marker of biological tissues, however they are challenging to be measured in-vivo. Non-invasive approaches to assess tissue biomechanics have been suggested, but there is a clear need for more accurate techniques for diagnosis, surgical guidance and treatment evaluation. Recently air-puff systems have been developed to study the dynamic tissue response, nevertheless the experimental geometrical observations lack from an analysis that addresses specifically the inherent dynamic properties. In this study a viscoelastic finite element model was built that predicts the experimental corneal deformation response to an air-puff for different conditions. A sensitivity analysis reveals significant contributions to corneal deformation of intraocular pressure and corneal thickness, besides corneal biomechanical properties. The results show the capability of dynamic imaging to reveal inherent biomechanical properties in vivo. Estimates of corneal biomechanical parameters will contribute to the basic understanding of corneal structure, shape and integrity and increase the predictability of corneal surgery. © 2014 Kling et al.Spanish Government FIS2011-25637, European Research Council ERC-2011 AdG-294099 to SM. FPI-BES-2009-024560 Pre-doctoral Fellowship to SK.Peer Reviewe

Finite element modeling for the dynamic biomechanical characterization of the in-vivo cornea

ARVO Annual Meeting, Orlando, United States, 4–8 May 2014Peer reviewe

Finite element modeling for the dynamic biomechanics characterization of the in-vivo cornea

Orlando, United States, 4–8 May 2014Mechanical properties give important information on the health of biological tissues. Recently new non-contact imaging element (FE) model to relate the measured geometrical deformation to the inherent corneal biomechanical parameters.Spanish Government FIS2011-25637, European Research Council ERC-2011 AdG-294099 to S. Marcos and FPIBES-2009-024560 Pre-doctoral Fellowship to S. KlingPeer Reviewe

Lentille intraoculaire à accommodation

[EN] Intraocular lens with accommodation capacity comprising a first optical member (1) having a dynamic optical power, to which a second optical member (2) with a fixed optical power is affixed, in such a manner that at least a central part of each of one of one of the curved surfaces (2a, 2b) of the second optical member (2) and of at least one of the surfaces (1a, 1b) of the first optical member (1) are in contact with each other, the second optical member (2) and the first optical member (1) providing a joint optical power which is variable between a condition of minimum optical power corresponding to a condition of disaccommodation and a condition maximum optical power corresponding to a condition of accommodation, and the first optical member and an anchoring system (3) being designed to change the curvature of at least one of the surfaces (1a, 1b) of the first optical element (1) progressively between a maximum curvature corresponding to the condition of accommodation in response to a minimum effective traction force of the ciliary muscle received through the anchoring system (3), and a maximum effective traction force of the ciliary muscle received by the anchoring system (3).[ES] Lente intraocular con capacidad de acomodación, que comprende un sistema de potencia óptica que comprende un primer elemento óptico (1) con una potencia óptica dinámica y variable y que comprende dos superficies (1a, 1b) correspondientes respectivamente a una superficie anterior (1a) y una superficie posterior (1b), al menos una de las cuales presenta una curvatura susceptible de deformarse elásticamente en respuesta a fuerzas de tracción del músculo ciliar del ojo, una región ecuatorial (1c) alrededor de dichas superficies (1a, 1b), así como un segundo elemento óptico (2) con una potencia óptica fija, con una cara curvada anterior (2a) y una cara curvada posterior (2b), estando el segundo elemento óptico (2) asociado al primer elemento óptico (1), de tal forma que el primer elemento óptico (1) y el segundo elemento óptico (2) conjuntamente tienen una potencia óptica conjunta determinada por una combinación de la potencia óptica fija del segundo elemento óptico (2) y la potencia óptica dinámica del primer elemento óptico (1), un sistema de anclaje (3) para anclar el primer elemento óptico (1) a al menos una parte del saco capsular del cristalino para transmitir al primer elemento óptico (1) fuerzas de tracción generadas por el músculo ciliar y transmitidas al saco capsular a través de fibras zonulares, comprendiendo el saco capsular, en estado natural, una cápsula anterior, una cápsula posterior y una cápsula ecuatorial, estando el sistema de anclaje (3) seleccionado entre mecanismos de sujeción mecánica, sistemas adhesivos biocompatibles, sistemas de microestructuras que propician fibrosis capsular, y combinaciones de los mismos, el segundo elemento óptico (2) está unido al primer elemento óptico (1) de tal forma que al menos sendas partes centrales de una de las caras curvadas (2a, 2b) del segundo elemento óptico (1) y de al menos una de las superficies (1a, 1b) del primer elemento óptico (1) están en contacto entre sí; la potencia óptica conjunta es variable entre un estado de potencia óptica mínima, correspondiente a un estado de desacomodación en el que la lente intraocular es susceptible de enfocar el ojo a una distancia de visión lejana, y un estado de acomodación en el que la lente intraocular es susceptible de enfocar el ojo a una distancia de visión de lectura; caracterizada por que - el primer miembro óptico (1) está fabricado de un material deformable preformado y tiene una curvatura máxima de la preforma predeterminada y una potencia óptica máxima en su posición de acomodación; el primer elemento óptico (1) y el sistema de anclaje (3) están diseñados para variar la curvatura de al menos una de las superficies (1a, 1b) del primer elemento óptico (1) progresivamente entre la curvatura máxima de la preforma predeterminada correspondiente al estado de acomodación máxima, en respuesta a una fuerza de tracción eficaz mínima del músculo ciliar recibida por el sistema de anclaje (3), y una curvatura mínima correspondiente al estado de desacomodación en respuesta a una fuerza de tracción eficaz máxima del músculo ciliar recibida por el sistema de anclaje (3); y por que: - el sistema de anclaje es un conjunto discreto de más de tres puntos de anclaje para anclar el primer elemento óptico (1) a al menos una porción del saco capsular del cristalino.Peer reviewedConsejo Superior de Investigaciones Científicas (España)B1 Patente sin examen previ

Air-puff Corneal Deformation Imaging to estimate Mechanical Properties in Normal and Treated corneas

7th World Congress of Biomechanics, Boston (USA), July 6-11, 2014Peer Reviewe