KEYWORDS: Depolarization, Signal to noise ratio, Eye, Retina, Tissues, Polarization, In vivo imaging, Optical calibration, Calibration, Image segmentation
SignificanceA data-based calibration method with enhanced depolarization contrast in polarization-sensitive optical coherence tomography (PS-OCT) was developed and demonstrated effective for detecting melanin content in the eye.AimWe aim to mitigate the dependence between the measured depolarization metric and the intensity signal-to-noise ratio (SNR) for improved visualization of depolarizing tissues, especially in low SNR regions, and to demonstrate the enhanced depolarization contrast to evaluate melanin presence.ApproachA function for calibrating the depolarization metric was experimentally derived from the young albino guinea pig, assuming depolarization free in the retina. A longitudinal study of guinea pigs (9 weeks) was conducted to assess the accumulation of melanin during early eye growth. Furthermore, the melanin content of the sub-macular choroid was compared in eyes with light and dark irides involving 14 human subjects in early middle adulthood.ResultsWe observed an increase in the improved depolarization contrast, which indicates potential melanin accumulation in the early eye development with age in the pigmented guinea pig eyes. We found a significant difference in melanin content between human eyes with light and dark colors.ConclusionsOur proposed calibration method enhanced the visualization of depolarizing structures in PS-OCT, which can be generalized to all kinds of polarization-sensitive imaging and can potentially monitor melanin in healthy and pathological eyes.
We report a pioneer clinical study using triple-input polarization-sensitive optical coherence tomography (TRIPS-OCT) to assess sub-macular scleral birefringence in 60 children with myopia. Results showed a significant difference in scleral birefringence between high and low myopia groups. In addition, we observed a correlation between axial length and birefringence in the low myopia group. This suggests the potential of using sub-macular scleral birefringence as a biomarker for myopia progression. Despite a high exclusion ratio due to inadequate scleral visibility and other limitations, these findings warrant further large-scale studies.
Polarization-sensitive OCT (PS-OCT) derives image contrast from tissue birefringence. Here, we introduced triple-input polarization sensitive optical coherence tomography (TRIPS-OCT), a new polarimetric modulation and reconstruction strategy for depth-resolved tomographic birefringence imaging in-vivo. We modulated the polarization states between three repeated frames and enabled the reconstruction of the Mueller matrix at each location within the triple-measured frames. We demonstrated a 2-fold reduction of the birefringence noise floor compared to the conventional dual-input reconstruction method, and a 3-fold reduction of the measurement error of optic axis orientation in retinal imaging with the compensation of corneal retardance and diattenuation.
We use the prototype swept-source (SS) OCT at 1060 nm to image human Schlemm’s canal (SC) and perform full reconstruction in the en face plane. Compared with spectral-domain (SD) OCT systems at 800 nm, the SS OCT system at 1060 nm offers deeper signal penetration, and has no sensitivity roll-off effect to allow for better localization and delineation of SC. One volumetric scan was taken from each of the eight cardinal positions to cover the entire SC circumferentially around the limbus. The en face slices were taken from each volume at the SC region, and were stitched together to generate an en face representation of the 360 deg SC.
We investigate the influence of the OCT system resolution on high-quality en face corneal endothelial cell images in vivo, to allow for quantitative analysis of cell density. We vary the lateral resolution of the ultrahigh-resolution (UHR) OCT system (centered at 850 nm) by using different objectives, and the axial resolution by windowing the source spectrum. We are able to obtain a high-quality en face corneal endothelial cell map in vivo using UHR OCT for the first time. Quantitative analysis result of cell density from in vivo en face corneal endothelial cell map agrees with previously reported data.
Choriocapillaris is a unique vascular plexus located posterior to the retinal pigment epithelium. In the recent years, there is an increasing interest to investigate choriocapillaris alteration and progression of eye diseases and aging, using the optical coherence tomography angiography (OCTA). However, standardized algorithm for analysis has not been developed. Herein, we present non-invasive, in-vivo, high-resolution images of the non-human primates’ choriocapillaris using OCTA. Images were acquired with a prototype swept-source OCTA (SS-OCTA) system with 100kHz A-scan/s rate, over regions of 3×3 mm2 and 12×12 mm2. The non-perfusion area, also called flow voids, were segmented with an intensity damped, illuminance-compensated algorithm. The optimized quantification of the choriocapillaris flow voids may have applications in a wide array of eye diseases including age-related macular degeneration (AMD) and visualization of choriocapillaris in animal models could aid future studies on choroid involvement in models of eye disease.
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