The path to clinical translation for visible light optical coherence tomography in retinal imaging

Visible light optical coherence tomography (VIS-OCT) has made significant progress in the past decade from in vivo proof-of-concept retinal imaging in preclinical models to human clinical translation. The technical advances of VIS-OCT imaging devices include new light sources, optical fiber components, balanced detection methods, and an array of data processing methods. We summarize the unique features of using VIS-OCT in comparison with near-infrared OCT (NIR-OCT), including ultra-high resolution, retinal microvascular oximetry, and reflectance spectroscopy. The ultra-high resolution is granted by the shorter wavelengths in the visible light range ~500-650 nm, as compared with the conventional OCT wavelengths >800 nm. Detailed sub-bandings in the inner plexiform layer and outer segment of photoreceptors, as well as in the retinal pigment epithelium and Bruch's membrane, are consistently resolved in VIS-OCT. The three-dimensional resolving capacity of VIS-OCT allows better isolation of hemoglobin absorption features, allowing blood oxygen saturation (SO₂) calculation in retinal microvasculature. Oximetry calculations were performed down to the capillary level in humans, albeit through massive averaging, which was unattainable by previous methods. Advancing VIS-OCT technology has a high potential to produce significant clinical impact in ophthalmology in the near future.