Impact of chamber pressure and material properties on the deformation response of corneal models measured by dynamic ultra-high-speed Scheimpflug imaging

Faria-Correia, Fernando; Ramos, Isaac; Roberts, Cynthia J.; Steinmueller, Andreas; Krug, Matthias; Ambrósio, Renato

doi:10.1590/s0004-27492013000500005

Cited by 26 publications

(14 citation statements)

References 26 publications

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“…Liu et al in [31] measured ultrasound wave propagation in soft contact lenses. Correia et al [32] measured Corvis ST corneal deformation amplitude on artificial corneas lathed on contact lens materials.…”

Section: Introductionmentioning

confidence: 99%

Material Properties from Air Puff Corneal Deformation by Numerical Simulations on Model Corneas

et al. 2016

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ObjectiveTo validate a new method for reconstructing corneal biomechanical properties from air puff corneal deformation images using hydrogel polymer model corneas and porcine corneas.MethodsAir 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.ResultsThe 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.ConclusionsAir 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.

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Section: Introductionmentioning

confidence: 99%

Material Properties from Air Puff Corneal Deformation by Numerical Simulations on Model Corneas

et al. 2016

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“…The UHS Scheimpflug camera enables to acquire a sequence of images of corneal deformation in response to an air puff . Based on additional analysis performed in the Corvis ST tonometer using the provided software, intraocular pressure (IOP) and other parameters of deformation are determined .…”

Section: Introductionmentioning

confidence: 99%

“…Such a situation also occurs in the case of analysis of images from the ultra-high-speed (UHS) Scheimpflug camera [7][8][9]which is used for example in the Corvis tonometer (Optikgeräte Oculus GmbH, Wetzlar, Germany) [10,11]. The UHS Scheimpflug camera enables to acquire a sequence of images of corneal deformation in response to an air puff [12][13][14][15][16]. Based on additional analysis performed in the Corvis ST tonometer using the provided software, intraocular pressure (IOP) and other parameters of deformation are determined [17][18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Scheimpflug camera in the quantitative assessment of reproducibility of high‐speed corneal deformation during intraocular pressure measurement

Koprowski

Ambrósio²,

Reisdorf

2015

Journal of Biophotonics

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The paper presents an original analysis method of corneal deformation images from the ultra-high-speed Scheimpflug camera (Corvis ST tonometer). Particular attention was paid to deformation frequencies exceeding 100 Hz and their reproducibility in healthy subjects examined repeatedly. A total of 4200 images with a resolution of 200 × 576 pixels were recorded. The data derived from 3 consecutive measurements from 10 volunteers with normal corneas. A new image analysis algorithm, written in Matlab with the use of the Image Processing package, adaptive image filtering, morphological analysis methods and fast Fourier transform, was proposed. The following results were obtained: (1) reproducibility of the eyeball reaction in healthy subjects with precision of 10%, (2) corneal vibrations with a frequency of 369 ± 65 Hz (3) and amplitude of 7.86 ± 1.28 µm, (4) the phase shift within two parts of the cornea of the same subject of about 150°. The result of image sequence analysis for one subject and deformations with a corneal frequency response above 100 Hz.

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“…Studies have demonstrated the importance of this new approach in the diagnosis of ectasia 11 , assessment of the crosslinking results in the corneal collagen in ceratocone 12 and the impact of the intraocular pressure in corneal deformation in an experimental study. 13 Our study is the first in the world to asess the biomechanical properties of the cornea by Corvis ST after phacoemulsification, and the first after the application of femtosecond laser in the cataract surgery. Both techniques seemed to alter the biomechanical properties of the cornea.…”

Section: Chartmentioning

confidence: 89%

Changes of corneal biomechanical after femtosecond laser–assisted for cataract surgery

Valbon¹,

Ambrósio²,

Gualdi³

et al. 2015

Revista Brasileira De Oftalmologia

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Impact of chamber pressure and material properties on the deformation response of corneal models measured by dynamic ultra-high-speed Scheimpflug imaging

Cited by 26 publications

References 26 publications

Material Properties from Air Puff Corneal Deformation by Numerical Simulations on Model Corneas

Material Properties from Air Puff Corneal Deformation by Numerical Simulations on Model Corneas

Scheimpflug camera in the quantitative assessment of reproducibility of high‐speed corneal deformation during intraocular pressure measurement

Changes of corneal biomechanical after femtosecond laser–assisted for cataract surgery

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