Doppler holography uses high-speed imaging with near-infrared laser light to reveal blood flow contrasts in the eye fundus. We estimate the velocity of blood flow, blood volume rate and resistivity changes in in-plane retinal arteries by segmenting retinal vessels and calculating the local difference in root-mean-square Doppler frequency broadening compared to the background. Our approach allows for the estimation of hemodynamics in in-plane retinal arteries throughout the cardiac cycle, offering significant potential in the diagnosis and monitoring of ocular vascular conditions.
We demonstrate the feasibility of a multimodal AO flood-illumination ophthalmoscope, able to provide both bright-field and dark-field images. The multimodality was made possible by integrating a digital micromirror device (DMD) at the illumination path to project a sequence of complementary high-resolution patterns into the retina. Owing to the given system, and the proposed acquisition/processing pipeline, we were able, at the same time, to: (1) obtain up to four-fold contrast improvement in bright-field modality when imaging highly scattered structures such as PRs and NFL; and (2) to visualize, through phase contrast images, translucent retinal features such as capillaries, red blood cells, vessel walls, ganglion cells, and PRs inner segment.
We presented the first clinical images generated with compact, clinical-adapted FFOCT. This was made possible thanks to the replacement of the former Adaptive Lens by a Woofer-Tweeter approach, combining a Variable Focal Lens for defocus correction, and the Phaseform’s Deformable Phase Plate for high-order aberrations correction, enabling to improve both SNR and lateral resolution when imaging patients.
Adaptive optics imaging techniques are invaluable for cellular-level retina visualization. While AO Flood illumination ophthalmoscopes provide distortion-free, high-speed images, they lack contrast. On the other hand, AO scanning laser ophthalmoscopes offer highly contrasted images due to point by point illumination and spatial filtering but suffer from low pixel throughput and distortion artifacts. Our recent advancements, using a DMD integrated AO-FIO, show that we can illuminate and capture multiple spatially separated zones, achieving contrast close to the one of a confocal microscope. Our theoretical framework emphasizes that each zone must be smaller than 100μm in both directions or smaller than 10μm in only one direction to minimize the diffuse light component. Building upon these results, we developed a cutting-edge confocal rolling slit ophthalmoscope, able to achieve brightfield contrast similar to a confocal ophthalmoscope, along with phase contrast images. We utilize a classical sCMOS camera with a rolling shutter synchronized with the line source scanning of the field of view. The system makes use of all the incident photons that can be collected, whether singly, multiply scattered or absorbed. Easy digital switching between the darkfield and brightfield, as well as modification of the size and offset of the detection aperture, enhances the adaptability and versatility of this multimodal imaging system, allowing for fine-tuning of imaging modalities and comprehensive exploration of the retina.
We developed a novel combined SD-OCT + TD-FF-OCT device that provides cell-resolution view of TD-FF-OCT without compromising SD-OCT performance. SD-OCT gives global view for eye exploration and FF-OCT shows cell-detail in the central region of the OCT scan. Eye imaging is fast enough to be part of the routine clinical exam (10 min/patient). Four patients with different eye pathologies were imaged. FF-OCT resolved: striae (stromal mechanical folds), guttata, loss of endothelial cells and stromal cuts following the surgery. Additionally, we could access the trabecular meshwork region of the eye and obtain the first images of meshwork fibers at micron resolution.
We present the first clinical uses of time-domain FF-OCT in Anterior eye. Four patients with different eye pathologies (keratoconus, Fuch's endothelial dystrophy, age-related changes, post-PRK surgery) were imaged as part of the routine clinical examination (10 min per patient). FF-OCT resolved micron–size pathologies: striae (mechanical folds of corneal stroma), guttata (excrescences in Descemet's membrane), loss of endothelial cells and stromal cuts following the surgery. High resolution (1.7 µm) makes FF-OCT a promising tool for diagnosis of diseases at earlier stages than was possible before and their effective treatment with medication instead of surgery.
We enhanced the capabilities of an Adaptive Optics Flood Illumination Ophthalmoscope to achieve multimodal imaging. The control of the illumination with a digital micromirror device, combined with a wide field of view and a light data processing, allows us to improve the brightfield contrast with a pseudo-confocal mode and to visualize transparent retinal structures with phase contrast imaging. We achieved to get from a single sequence of acquisition, four wide field images, each corresponding to one type of the following imaging modes: contrast-enhanced brightfield, darkfield, offset aperture and split-detection imaging.
We present a digital method to reveal the axial direction of local blood flow based on the Doppler spectrum asymmetry, called directional contrast. This contrast is overlaid on standard grayscale blood flow images to depict flow towards the camera in red, and flow away from the camera in blue. The local direction of blood flow with respect to the optical axis can be revealed with a high temporal resolution in out-of-plane retinal vessels, allowing to evidence potential blood flow reversal. We demonstrate this capability in an eye affected by high tension glaucoma and central retinal vein occlusion, in which we found a significant diastolic arterial retrograde flow.
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