Second-generation dual-channel visible light optical coherence tomography enables wide-field, full-range, and shot-noise limited human retinal imaging

Abstract

Abstract Visible light optical coherence tomography (VIS-OCT) is an emerging ophthalmic imaging method featuring ultrahigh depth resolution, retinal microvascular oximetry, and distinct scattering contrast in the visible spectral range. The clinical utility of VIS-OCT is hampered by the fundamental trade-off between the imaging depth range and axial resolution, which are determined by the spectral resolution and bandwidth, respectively. While the full potential of VIS-OCT is leveraged by a broad bandwidth, the imaging depth is inversely sacrificed. The effective depth range is further limited, especially in the shorter wavelengths, by the spectrally dependent roll-off of the signal-to-noise ratio (SNR). To address this trade-off, we developed a second-generation (2nd Gen) dual-channel VIS-OCT system with three major advancements including the first linear-in-K VIS-OCT spectrometer to decrease the roll-off, reference pathlength modulation to expand the imaging depth range, and per-A-line noise cancellation to remove excess noise, Due to these unique designs. this system achieves 7.2 dB roll-off over the full 1.74 mm depth range (water) with shot-noise limited performance. The system uniquely enables > 60° wide-field imaging which would allow simultaneous imaging of the peripheral retina and optic nerve head, as well as ultrahigh 1.3 µm depth resolution (water). Benefiting from the additional near-infrared (NIR) channel of the dual-channel design, this system was compatible with Doppler OC T and OCT angiography (OCTA). The comprehensive structure-function measurements enabled by this second-generation dual-channel VIS-OCT system is a significant advance towards adoption of VIS-OCT in clinical applications.