Abstract
Purpose :
Corneal biomechanical properties are inherently tied to its shape and function but noncontact measurements of corneal biomechanical properties can be difficult due to physiological motion. In this work, we developed and tested an ultra-fast line-field optical coherence elastography (LFOCE) system capable of single-shot measurements of wave propagation in the cornea.
Methods :
We developed a parallel line-field spectral domain optical coherence tomography system based on a supercontinuum laser (EXR-9 OCT, NKT Photonics) and a line-field Michelson interferometer. The spectral interference was imaged onto a high speed 2D camera (Phantom v2512, Vision Research). An air-pulse induced elastic waves, which were imaged by the LFOCE system. Figure 1 is a schematic of the system. The equivalent A-scan rate was 11.5 MHz based on 460 spatial pixels with a framerate of 25 kHz.
Validation measurements with LFOCE and uniaxial mechanical testing were made in tissue-mimicking gelatin phantoms (8%, 10%, and 12% w/w, N=3 of each type). Measurements were made in in situ and in vivo rabbit corneas. In vivo measurements were made in an anesthetized rabbit, and all procedures were approved by the University of Houston Institutional Animal Care and Use Committee.
Results :
The LFOCE-measured elasticity of the 8%, 10%, and 12% phantoms was 13.8 ± 1.5 kPa, 21.4 ± 2.8 kPa, and 32.5 ± 3.1 kPa, respectively. Mechanical testing measured the stiffness of the 8%, 10%, and 12% phantoms as 15.6 ± 1.8 kPa, 23.7± 2.1 kPa, and 36.1 ± 1.6 kPa, respectively. Figure 2 shows the elastic wave propagation in the in situ rabbit cornea at 10 mmHg IOP at the noted times after excitation. The average wave speed of 3 repeated measurements in the in situ cornea at 10, 15, and 20 mmHg IOP was 3.03 ± 0.05 m/s, 4.66 ± 0.03 m/s, and 8.85 ± 0.08 m/s, respectively. In the in vivo rabbit cornea, the wave speed was 11.10 ± 0.32 m/s.
Conclusions :
The LFOCE system was capable of imaging the wave propagation in the cornea successfully in a single shot. Future work will focus on improving the system sensitivity, incorporating a scanner for 3D imaging, and reducing the spectral band imaged by the camera to adhere to safety limits.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.