Our data indicate that all three layers of the posterior cornea can be clearly visualized in vivo and their thicknesses measured precisely with UHR-OCT. Although the PDL thickness showed large spatial variations, the thickness of the DM and END layers was consistent over the entire imaged region of the cornea.

PURPOSE. To correlate visually evoked functional and blood flow changes in the rat retina measured simultaneously with a combined optical coherence tomography and electroretinography system (OCTþERG).METHODS. Male Brown Norway (n ¼ 6) rats were dark adapted and anesthetized with ketamine/xylazine. Visually evoked changes in the retinal blood flow (RBF) and functional response were measured simultaneously with an OCTþERG system with 3-lm axial resolution in retinal tissue and 47-kHz image acquisition rate. Both single flash (10 and 200 ms) and flicker (10 Hz, 20% duty cycle, 1-and 2-second duration) stimuli were projected onto the retina with a custom visual stimulator, integrated into the OCT imaging probe. Total axial RBF was calculated from circular Doppler OCT scans by integrating over the arterial and venal flow.RESULTS. Temporary increase in the RBF was observed with the 10-and 200-ms continuous stimuli (~1% and~4% maximum RBF change, respectively) and the 10-Hz flicker stimuli (~8% for 1-second duration and~10% for 2-second duration). Doubling the flicker stimulus duration resulted in~25% increase in the RBF peak magnitude with no significant change in the peak latency. Single flash (200 ms) and flicker (10 Hz, 1 second) stimuli of the same illumination intensity and photon flux resulted in~23 larger peak RBF magnitude and~25% larger RBF peak latency for the flicker stimulus.CONCLUSIONS. Short, single flash and flicker stimuli evoked measureable RBF changes with larger RBF magnitude and peak latency observed for the flicker stimuli.

A research-grade OCT system was used to image in-vivo and without contact with the tissue, the cellular structure and microvasculature of the healthy human corneo-scleral limbus. The OCT system provided 0.95 µm axial and 4 µm (2 µm) lateral resolution in biological tissue depending on the magnification of the imaging objective. Cross-sectional OCT images acquired tangentially from the inferior limbus showed reflective, loop-like features that correspond to the fibrous folds of the palisades of Vogt (POV). The high OCT resolution allowed for visualization of individual cells inside the limbal crypts, capillaries extending from the inside of the POV's fibrous folds and connecting to a lateral grid of micro-vessels located in the connective tissue directly below the POV, as well as reflections from individual red blood cells inside the capillaries. Difference in the reflective properties of the POV was observed among subjects of various pigmentation levels of the POV. Morphological features observed in the high resolution OCT images correlated well with histology. The ability to visualize the limbal morphology and microvasculature in-vivo at cellular level can aid the diagnostics and treatment of limbal stem cell dysfunction and dystrophies. a novel anatomical structure and a putative limbal stem cell niche," Br.

To use machine learning in those with brain amyloid to predict thioflavin fluorescence (indicative of amyloid) of retinal deposits from their interactions with polarized light. Methods: We imaged 933 retinal deposits in 28 subjects with post mortem evidence of brain amyloid using thioflavin fluorescence and polarization sensitive microscopy. Means and standard deviations of 14 polarimetric properties were input to machine learning algorithms. Two oversampling strategies were applied to overcome data imbalance. Three machine learning algorithms: linear discriminant analysis, supporting vector machine, and random forest (RF) were trained to predict thioflavin positive deposits. For each method; accuracy, sensitivity, specificity, and area under the receiver operating characteristic curve were computed. Results: For the polarimetric positive deposits, using 1 oversampling method, RF had the highest area under the receiver operating characteristic curve (0.986), which was not different from that with the second oversampling method. RF had 95% accuracy, 94% sensitivity, and 97% specificity. After including deposits with no polarimetric signals, polarimetry correctly predicted 93% of thioflavin positive deposits. Linear retardance and linear anisotropy were the dominant polarimetric properties in RF with 1 oversampling method, and no polarimetric properties were dominant in the second method. Conclusions: Thioflavin positivity of retinal amyloid deposits can be predicted from their images in polarized light. Polarimetry is a promising dye-free method of detecting amyloid deposits in ex vivo retinal tissue. Further testing is required for translation to live eye imaging. Translational Relevance: This dye-free method distinguishes retinal amyloid deposits, a promising biomarker of Alzheimer's disease, in human retinas imaged with polarimetry.

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