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Yuanyuan Wang, Zi Jin, Sisi Chen, Dexi Zhu, Meixiao Shen, Fan Lu; Quantitative assessment of corneal viscoelasticity using elastic wave optic coherence elastography. Invest. Ophthalmol. Vis. Sci. 2019;60(9):6812. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
In this work, we originate the novel analysis method which comprehensively utilized the elastic wave velocity, frequency and power attenuation to assess the corneal viscoelasticity.
Inducing the elastic wave by the piezoelectric transducer (PZT), we used the M-B scan of phase-resolved optical coherence tomography (OCT) to detect and characterize the elastic wave. Firstly, Spatial-temporal Doppler phase images of the sample visualized the elastic wave propagation along the lateral direction, whose phase velocities were calculated according to the slope of the black dotted line in Fig. 1(b). Secondly, we transformed Spatial-temporal Doppler phase into the wavenumber-frequency domain by using the 2D discrete Fast Fourier Transform to acquire the center angular frequency of elastic wave marked as the green star in Fig. 1(c). Based on the Doppler phase, then we can get the power distribution along the elastic wave propagation and estimate the power attenuation coefficient through exponential curve fitting in Fig. 1(d). Finally, we assessed the sample quantificationally by the Kelvin-Voigt model. The experiments were performed on 0.5% homogeneous agar phantoms (n=3), 1.0% homogeneous agar phantoms (n=3) and the fresh porcine corneas (n=2).
As expect, we found that the Young’s modulus of 1% agar phantom (54.45±2.268 Kpa) was about 4 times 0.5% agar phantom (14.95±1.949 Kpa), and the viscous modulus of both were similar (0.722 VS 0.502 Pa.s). The Young’s modulus of porcine corneas (15.93±2.437 Kpa) was close to 0.5% agar phantom, but the viscous modulus (3.667±0.707 Pa.s) was much larger than agar phantoms significantly.
This new elastic wave analysis method has the capability to assess the corneal viscoelasticity.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
Fig. 1. Elastic wave result in fresh porcine cornea. (a) The B-scan OCT porcine cornea image, of which the anterior and posterior surface are segmented by green solid line and blue solid line, respectively. (b) The spatial-temporal Doppler images. The elastic wave velocity is calculated according to the slope of the black dotted line. (c) Wavenumber-frequency domain of elastic wave. The center frequency of elastic wave is marked as the green star. (d) The power distribution. The original data is labeled by blue circle, and the fitting curve is marked by red solid line.
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