Probing dynamic processes in the eye at multiple spatial and temporal scales with multimodal full field OCT

Abstract

et al.. Probing dynamic processes in the eye at multiple spatial and temporal scales with multimodal full field OCT. Abstract:We describe recent technological progress in multimodal en face full-field optical coherence tomography that has allowed detection of slow and fast dynamic processes in the eye. We show that by combining static, dynamic and fluorescence contrasts we can achieve label-free high-resolution imaging of the retina and anterior eye with temporal resolution from milliseconds to several hours, allowing us to probe biological activity at subcellular scales inside 3D bulk tissue. Our setups combine high lateral resolution over a large field of view with acquisition at several hundreds of frames per second which make it a promising tool for clinical applications and biomedical studies. Its contactless and non-destructive nature is shown to be effective for both following in vitro sample evolution over long periods of time and for imaging of the human eye in vivo.

Real-time non-contact cellular imaging and angiography of human cornea and limbus with common-path full-field/SD OCT

“…Previously, we demonstrated the possibility of local blood flow measurements from the conjunctival surface using manually drawn kymograph plots (i.e. plotting the vessel curvilinear abscissa against time) 42 . Unfortunately, each plot provided only a single local velocity value, so that obtaining a full-field velocity map would require considerable manual effort.…”

Kilohertz retinal FF-SS-OCT and flood imaging with hardware-based adaptive optics

“…A related method is FF time-domain (TD) OCT using white light [39], which sidesteps entirely the impact of aberrations on resolution (but not sensitivity) by employing high spatial coherence to filter the photons misplaced by optical aberrations. Phase perturbations manifesting in speckle have been used to visualize subcellular dynamics in tissue explants and the human cornea [35], and may represent a complementary retinal imaging modality, especially when equipped with axial eye tracking [27]. DAC has also been employed in line-scanning TD-OCT, which mitigates the contributions of axial motion to the phase of the interference fringe [13].…”

Motion artifact removal and signal enhancement to achieve in vivo dynamic full field OCT

“…The reference arm contains a silicon mirror mounted on a piezoelectric translation (PZT) used for phase modulation. In a typical FFOCT experiment, at least two images are acquired with different phase modulations and the FFOCT image is constructed by using appropriate phase-shifting algorithms [4,11]. For D-FFOCT experiments the PZT position is not modulated, fluctuations arise by scatterers motions inside the coherence volume.…”

“…A similar technique is used in regular OCT for retinal angiography called OCTA where speckle variance is analyzed on several B-Scans (typically 8 frames) to produce binary images of the retinal vasculature [10]. Due to the high spatial resolution (< 1 µm) and the number of frames used in D-FFOCT (typically 512), our method is not only sensitive to capillaries but also to intracellular motility signals and produces a contrast that reveals living cells [11]. The penetration depth of D-FFOCT is typically ten times less than FFOCT due to the small cross-section of the moving scatterers leading to weak signals, limiting its use in thick samples.…”