Quantitative assessment of corneal viscoelasticity using optical coherence elastography and a modified Rayleigh–Lamb equation

Han, Zhaolong; Aglyamov, Salavat R.; Li, Jiasong; Singh, Manmohan; Wang, Shang; Vantipalli, Srilatha; Wu, Chen; Liu, Chih-Hao; Twa, Michael D.; Larin, Kirill V.

doi:10.1117/1.jbo.20.2.020501

Cited by 90 publications

(78 citation statements)

References 18 publications

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“…We have previously developed a method of obtaining the viscoelasticity of the cornea by utilizing a modified Rayleigh Lamb Frequency Equation (RLFE), which was adjusted to include the effects of the solid-fluid boundary at the corneal posterior surface [54]. While this model incorporated the thickness of the cornea, it neglected the curvature of the cornea by assuming the cornea was a thin plate in infinite half-space.…”

Section: Discussionmentioning

confidence: 99%

“…Extrapolating our previously developed modified RLFE [54] to a multi-layered geometry would produce more unknowns than equations making the system unsolvable. Development of a multi-layered model that correctly incorporates the boundary conditions between the layers of the cornea yielding depth-resolved viscoelastic quantifications is currently in progress.…”

Section: Discussionmentioning

confidence: 99%

“…The group velocity of the air-pulse induced elastic wave was used to quantify the Young’s modulus [45], and spectral analysis revealed the depth-wise micro-scale elasticity distribution of the various layers of the cornea [51]. Furthermore, the phase velocities obtained over the bandwidth of the air-pulse excitation were used in conjunction with a modified Rayleigh-Lamb Frequency Equation (RFLE) to provide a more robust assessment of corneal viscoelasticity [54] as compared to Young’s modulus quantifications based solely on the group velocity [55]. While these techniques have provided valuable information about the biomechanical properties of the cornea, they were predominantly focused on unidirectional investigations.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Noncontact Elastic Wave Imaging Optical Coherence Elastography for Evaluating Changes in Corneal Elasticity Due to Crosslinking

Singh

Vantipalli

et al. 2016

IEEE J. Select. Topics Quantum Electron.

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The mechanical properties of tissues can provide valuable information about tissue integrity and health and can assist in detecting and monitoring the progression of diseases such as keratoconus. Optical coherence elastography (OCE) is a rapidly emerging technique, which can assess localized mechanical contrast in tissues with micrometer spatial resolution. In this work we present a noncontact method of optical coherence elastography to evaluate the changes in the mechanical properties of the cornea after UV-induced collagen cross-linking. A focused air-pulse induced a low amplitude (μm scale) elastic wave, which then propagated radially and was imaged in three dimensions by a phase-stabilized swept source optical coherence tomography (PhS-SSOCT) system. The elastic wave velocity was translated to Young’s modulus in agar phantoms of various concentrations. Additionally, the speed of the elastic wave significantly changed in porcine cornea before and after UV-induced corneal collagen cross-linking (CXL). Moreover, different layers of the cornea, such as the anterior stroma, posterior stroma, and inner region, could be discerned from the phase velocities of the elastic wave. Therefore, because of noncontact excitation and imaging, this method may be useful for in vivo detection of ocular diseases such as keratoconus and evaluation of therapeutic interventions such as CXL.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Noncontact Elastic Wave Imaging Optical Coherence Elastography for Evaluating Changes in Corneal Elasticity Due to Crosslinking

Singh

Vantipalli

et al. 2016

IEEE J. Select. Topics Quantum Electron.

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“…25 However, most of these wave-related models are based on the assumption that the sample is a thin plate, which does not account for the curved shape of the cornea. Furthermore, variations in the corneal thickness are another important parameter that can affect the elastic wave propagation, but the effects of the curvature and thickness on the propagation of an elastic wave in the cornea are not well understood.…”

mentioning

confidence: 99%

“…24 Recently, we have proposed a modified Rayleigh-Lamb frequency equation to investigate the viscoelasticity of the cornea by incorporating the effects of the solid-fluid interface at the corneal posterior surface. 25 However, most of these wave-related models are based on the assumption that the sample is a thin plate, which does not account for the curved shape of the cornea. Furthermore, variations in the corneal thickness are another important parameter that can affect the elastic wave propagation, but the effects of the curvature and thickness on the propagation of an elastic wave in the cornea are not well understood.…”

mentioning

confidence: 99%

Analysis of the effects of curvature and thickness on elastic wave velocity in cornea-like structures by finite element modeling and optical coherence elastography

Han

Singh

et al. 2015

Applied Physics Letters

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Wave models that have been used to extract the biomechanical properties of the cornea from the propagation of an elastic wave are based on an assumption of thin-plate geometry. However, this assumption does not account for the effects of corneal curvature and thickness. This study conducts finite element (FE) simulations on four types of cornea-like structures as well as optical coherence elastography (OCE) experiments on contact lenses and tissue-mimicking phantoms to investigate the effects of curvature and thickness on the group velocity of an elastic wave. The elastic wave velocity as determined by FE simulations and OCE of a spherical shell section decreased from $2.8 m/s to $2.2 m/s as the radius of curvature increased from 19.1 mm to 47.7 mm and increased from $3.0 m/s to $4.1 m/s as the thickness of the agar phantom increased from 1.9 mm to 5.6 mm. Both the FE simulation and OCE results confirm that the group velocity of the elastic wave decreases with radius of curvature but increases with thickness. These results demonstrate that the effects of the curvature and thickness must be considered in the further development of accurate wave models for reconstructing biomechanical properties of the cornea. Assessing the biomechanical properties of the cornea is of great importance for detecting and monitoring the progression of ocular diseases, such as keratoconus, as well as evaluating the effectiveness of therapies, such as UVinduced collagen cross-linking. 1 In recent years, a number of noninvasive techniques have been proposed to characterize corneal biomechanical properties. For instance, the CorVis can image corneal dynamic responses from a strong air-puff stimulation, 2 and Brillouin microscopy is able to show the depth-resolved Brillouin frequency shift distribution of the cornea.3 Although these methods can provide important measurements that reflect the biomechanical characteristics of the cornea, directly quantifying the viscoelasticity of the cornea by these techniques is still a challenge.Optical coherence elastography (OCE) is a rapidly emerging method that can noninvasively measure the local biomechanical properties of tissues.4 OCE is similar to other elastographic techniques such as ultrasound elastography (USE), 5 magnetic resonance elastography (MRE), 6 and supersonic shear wave imaging (SSI) 7-9 where an externally induced deformation is measured by the respective imaging modality. OCE has micrometer scale spatial resolution 10 and millisecond temporal resolution but has a limited penetration depth of a few millimeters in scattering media such as tissue. However, penetration depth is not an issue for corneal imaging, and thus, OCE is specifically suitable for obtaining the biomechanical properties of the cornea. In our previous work, an OCE system comprised of an external noncontact loading device and an optical coherence tomography (OCT) system was utilized for tumor detection, 11 lens, 12 cornea, 13 cartilage, 14 and cardiac muscle 15 elasticity estimations. Although we have utilized a fo...

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Assessment of corneal viscoelasticity using elastic wave optical coherence elastography

Jin

Zhou

Shen

et al. 2019

Journal of Biophotonics

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The corneal viscoelasticity have great clinical significance, such as the early diagnosis of keratoconus. In this work, an analysis method which utilized the elastic wave velocity, frequency and energy attenuation to assess the corneal viscoelasticity is presented. Using phase‐resolved optical coherence tomography, the spatial‐temporal displacement map is derived. The phase velocity dispersion curve and center frequency are obtained by transforming the displacement map into the wavenumber‐frequency domain through the 2D fast Fourier transform (FFT). The shear modulus is calculated through Rayleigh wave equation using the phase velocity in the high frequency. The normalized energy distribution is plotted by transforming the displacement map into the spatial‐frequency domain through the 1D FFT. The energy attenuation coefficient is derived by exponential fitting to calculate the viscous modulus. Different concentrations of tissue‐mimicking phantoms and porcine corneas are imaged to validate this method, which demonstrates that the method has the capability to assess the corneal viscoelasticity.

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Quantitative assessment of corneal viscoelasticity using optical coherence elastography and a modified Rayleigh–Lamb equation

Cited by 90 publications

References 18 publications

Noncontact Elastic Wave Imaging Optical Coherence Elastography for Evaluating Changes in Corneal Elasticity Due to Crosslinking

Noncontact Elastic Wave Imaging Optical Coherence Elastography for Evaluating Changes in Corneal Elasticity Due to Crosslinking

Analysis of the effects of curvature and thickness on elastic wave velocity in cornea-like structures by finite element modeling and optical coherence elastography

Assessment of corneal viscoelasticity using elastic wave optical coherence elastography

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