Reverberant optical coherence elastography for measuring elasticity distribution in the porcine cornea ex vivo

Abstract

Purpose : The elastic properties of the cornea play a crucial role in eye health. Present clinical methods mainly focus on global deformation responses and cannot provide detailed spatial elasticity distribution. This work explores a novel technique utilizing a reverberant optical coherence elastography (OCE) approach for assessing corneal elastic heterogeneity in porcine cornea ex vivo before and after crosslinking (CXL).

Methods : The measurements were made using a phase-sensitive optical coherence tomography (OCT) system with a ~840 nm central wavelength, ~49 nm bandwidth, and A-line acquisition speed of 50 kHz. A 3D-printed ring with 8 contact legs was attached to a piezoelectric actuator connected to an amplifier. The legs were in contact with the peripheral part of the cornea. A 5 kHz sinusoidal signal was used to drive the actuator. The OCE data was acquired in 3D using 700 A-lines at 101 by 101 positions over a 5.5 by 5.3 mm area. Half of the cornea was crosslinked using the standard Dresden protocol. The OCE measurements were performed before CXL and after CXL for 30 minutes at 10-minute intervals. The intraocular pressure was kept at 15 mmHg. The local wave number and velocity were determined by fitting the 2D autocorrelation to the analytical solution for the reverberant shear wave model.

Results : The wave propagation process and velocity distribution in the untreated cornea are shown in Fig.1. Figure 2 demonstrates the changes in corneal geometry, wave propagation, and spatial velocity distribution at 0, 10, 20, and 30 min after crosslinking. The elastic waves in the crosslinked part of the cornea demonstrated higher wavelength and speed than the untreated part. Also, the upper crosslinked layers of the cornea show higher speed (stiffness) than the untreated part.

Conclusions : We demonstrate the feasibility of reverberant OCE to provide a spatial map of corneal elasticity in axial and lateral directions. The obtained elasticity map permits quantifying the elasticity distribution changes after crosslinking.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

Figure 1. Reverberant OCE in the cornea before crosslinking. (a) Elastic wave propagation; (b) B-mode; (c) Map of elastic wave velocity.

 

Figure 2. Reverberant OCE in the cornea after partial crosslinking. (a) Elastic wave propagation; (b) B-mode; (c) Maps of elastic wave velocity for different times after crosslinking.