Abstract
Purpose :
To develop and test the performance of a line-field SD-OCT (LF-SD-OCT) with 2.5 kHz frame rate and ~ 2.5 µm isotropic resolution in biological tissue, for in-vivo, non-contact imaging of the cellular structure of the human cornea.
Methods :
We have developed a LF-SD-OCT system for in-vivo, non-contact imaging of the cellular structure of the human cornea. The system is powered by a femtolaser with emission spectrum centered at 790 nm and spectral bandwidth of 130 nm, resulting in 1.8 µm axial OCT resolution. A cylindrical lens is used to project a line-shaped imaging beam at the corneal surface. By using 5x and 10x microscope objectives, we were able to achieve FOV of 2.6 mm x 1.3 mm and 1.3 mm x 1.3 mm respectively, and lateral resolution of ~5 µm to ~ 2.5 µm respectively. The detection end of the LF-SD-OCT is comprised of a transmission grating spectrometer and a fast 2D camera (1920 x 1080 pixels). The line scan rate of the system was ~2,500 B-scans/s. The system's SNR was measured to be ~92 dB at ~ 100 µm away from the zero-delay line for 2.8 mW imaging power. The system's SNR roll-off was ~17 dB over a scanning range of 1 mm. Volumetric (1080 x 400 x 960) images of the healthy human corneas were acquired both ex- and in-vivo from locations slightly inferior relative to the corneal apex in order to avoid the strong back reflections at the apex.
Results :
The cross-sectional corneal image in Fig. 1A shows very clear delineation of the boundaries of the Bowman's membrane with the epithelial layer and the anterior stroma. The collagen structure of the stroma is also visible. Figures 1B-1F show the same volumetric data with enface projections at various depths inside the cornea. Stomal keratocytes can be clearly resolved in both the volumetric image (Fig. 1F) and the corresponding enface image (Fig. 1G).
Conclusions :
Currently, LS-SD-OCT is able to map the morphology of the human cornea. The next step is to combine the LS-SD-OCT with numerical adaptive optics in order to visualize the cellular and sub-cellular structure of the corneal tissue from OCT images acquired in-vivo.
This abstract was presented at the 2019 ARVO Imaging in the Eye Conference, held in Vancouver, Canada, April 26-27, 2019.