Abstract
Purpose :
The recently developed visible-light OCT (vis-OCT) enabled an axial resolution of 1.3 µm, enhanced tissue scattering contrast, and introduced new functional imaging capabilities. These capabilities are increasingly desirable in the clinic. However, its clinical translation is limited by supercontinuum light sources with high relative-intensity noise (RIN), which degrades image quality and limits imaging speed. Therefore, we seek to develop a high-speed vis-OCT by eliminating RIN.
Methods :
We developed a vis-OCT, which uses two subpixel calibrated spectrometers in a Mach-Zehnder interferometer (MZI) to achieve balanced detection and RIN cancelation. We first coupled a supercontinuum light source (NKT Photonics, 78 MHz repetition rate) into a 10:90 fiber coupler. We delivered 10% of the light to the eye (200 µW) and 90% of the light to a transmission-based reference arm. Light backscattered from the eye was transmitted to a second 50:50 fiber coupler and was simultaneously detected by two well-calibrated spectrometers (Blizzard, Opticent Health).
Results :
Compared with the previous vis-OCT influenced by RIN, balanced detection achieved nearly shot-noise-limited imaging in humans, reduced the noise floor by 20.5 dB, increased the peak signal to the noise floor ratio from 16.1 dB to 31.8 dB, and increased the contrast to noise ratio from -9.7 dB to 3.8 dB (Figs. 1a&1b). We performed all imaging at a 125 kHz A-line rate with a field-of-view up to 10 mm × 4 mm (1024 A-lines × 256 B-scans) as shown in Fig. 1c, the fastest ever for ophthalmic vis-OCT.
Conclusions :
We developed the first subpixel-calibrated balanced detection MZI for significant RIN suppression in retinal vis-OCT. RIN suppression enabled the highest speed vis-OCT imaging at 125 kHz and the largest field-of-view in humans.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.