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Omkar C Thaware, Elias Pavlatos, Shuibin Ni, Yan Li, Yifan Jian, David Huang; Application of optical coherence elastography for corneal stiffness measurement.. Invest. Ophthalmol. Vis. Sci. 2022;63(7):1197 – A0197.
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© ARVO (1962-2015); The Authors (2016-present)
To determine corneal elastic modulus with optical coherence elastography (OCE). The OCE technology is eventually aimed to determine efficacy of a novel corneal collagen crosslinking (CXL) protocol by measuring corneal elastic modulus.
Ex-vivo experiments on three enucleated adult rabbit eyes were performed. A custom benchtop 100 kHz, 5-μm axial resolution swept-source optical coherence tomography (SS-OCT) system operating at 1060 nm wavelength was built. Corneoscleral discs were mounted on an artificial anterior chamber with closed-loop intracameral pressure control using a micro-infusion pump and pressure sensor. A speckle tracking method was used by locating the maximum cross-correlation between multipixel kernels. Local tissue displacements were tracked during a stepwise quasistatic mechanical loading with a intracameral pressure increment from 17 to 25 mmHg (Figure 1). B-M mode OCT scanning was used to obtain 2-D cross-section scan from central 6-mm of cornea. Corneal axial strain tensor (perpendicular to the corneal surface) was calculated as, Ezz(x,z) ≡ dUz(x,z) ÷ dX where Uz(x,z) represents the local axial displacements. Using the assumptions of homogeneity and uniform thickness, compressive (known as out-of-plane) Young’s modulus was calculated.
The average central corneal thickness of all three eyes was 480 microns. The axial strain profile was plotted (Figure 2) and the compressive Young’s modulus was measured as 23.4 kPa, 48.1 kPa and 49.1 kPa for all three corneas.
The measured compressive Young’s modulus is within the literature range of approximately 35 to 80 kPa. The OCE will be crucial for post-CXL biomechanical efficacy on intact corneal tissue under normal physiological pressure of 10 to 18 mmHg.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.
OCT cross-section over the central 6 mm of a cornea. Displacement vector (red arrow) was measured using speckle tracking where the original kernel (A- yellow window) was displaced to a new location (B- pink window) after the intracameral pressure increment from 19 to 20 mmHg.
The axial strain vs. stress profile for three rabbit corneas during an intracameral pressure elevation of 17 to 25 mmHg.
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