Fiber-based visible and near infrared optical coherence tomography (vnOCT) enables quantitative elastic light scattering spectroscopy in human retina

Abstract

Elastic light scattering spectroscopy (ELSS) has been proven a powerful method in measuring tissue structures with exquisite nanoscale sensitivity. However, ELSS contrast in the living human retina has been relatively underexplored, primarily due to the lack of imaging tools with a large spectral bandwidth. Here, we report a simple all fiber-based setup to implement dual-channel visible and near infrared (NIR) optical coherence tomography (vnOCT) for human retinal imaging, bridging over a 300nm spectral gap. Remarkably, the fiber components in our vnOCT system support single-mode propagation for both visible and NIR light, both of which maintain excellent interference efficiencies with fringe visibility of 97% and 90%, respectively. The longitudinal chromatic aberration from the eye is corrected by a custom-designed achromatizing lens. The elegant fiber-based design enables simultaneous imaging for both channels and allows comprehensive ELSS analysis on several important anatomical layers, including nerve fiber layer, outer segment of the photoreceptors and retinal pigment epithelium. This vnOCT platform and method of ELSS analysis open new opportunities in understanding structure-function relationship in the human retina and in exploring new biomarkers for retinal diseases.

Visible light optical coherence tomography angiography (vis-OCTA) and local microvascular retinal oximetry in human retina

“…This may be a limiting factor for large-scale clinical applications. Alternatively, we could use a dualchannel system with both visible and conventional near infrared (NIR) wavelengths to simultaneously acquire OCTA images [7,36]. While the NIR channel could provide rapid OCTA with a larger FOV for vessel localization, the co-registered vis-OCT structural data could provide spectral contrast for sO2.…”

“…The vis-OCT system is modified from our previous visible and near infrared OCT setup, with only the visible light channel operating ( Fig. 1a) [7]. Two edge filters selected the illumination wavelength range from 545 to 580 nm ( Fig.…”

“…Visible light optical coherence tomography (vis-OCT) [1][2][3][4][5][6][7][8][9][10][11] is a new derivation of OCT that uses visible light laser illumination instead of a conventional near-infrared (NIR) light [12]. One advantage of vis-OCT is its spatio-spectral analysis within the microvasculature for label-free oximetry (i.e.…”

Hyperspectral optical coherence tomography for in vivo visualization of melanin in the retinal pigment epithelium

“…Another recent study compared the reflectivity contrast between visible light OCT and near‐infrared OCT in the RPE, indicating that the difference in melanin absorption between these two wavelength bands may lead to an intrinsic contrast, detected by the intensity ratio of the OCT images. . All of these techniques make use of the absorption properties of melanin as the source of image contrast and therefore the melanin concentration must be sufficiently high to achieve good image contrast.…”

Early detection of retinal alteration by visible and near-infrared optical co-herence tomography (vnOCT) in a dexamethasone-induced ocular hypertension mouse model

“…First, this technology allows functional measurement of hemoglobin oxygen saturation (sO2) as there is strong hemoglobin absorption in visible light range and by extension allows calculation of the inner retina oxygen metabolic rate (MRO2) when combining blood flow measurements 19 . Second, by comparing the reflected signal between visible light and near-infrared (NIR) OCT images, the light scattering spectroscopic (LSS) contrast can detect ultrastructural changes in the retina, on a length scale beyond the resolution limit of current commercial imaging devices [20][21][22] . This LSS contrast can be quantified by a novel optical marker called the VN ratio that normalizes the visible light OCT images with NIR ones.…”