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Pedro Mecê, Jules Scholler, Kassandra Groux, Olivier Thouvenin, Mathias Fink, Kate Grieve, Claude Boccara; 1-mm field-of-view imaging of living human foveal cone mosaic with Full-Field OCT. Invest. Ophthalmol. Vis. Sci. 2020;61(7):216.
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Allying high cellular resolution in all three dimensions with a wide field-of-view (FOV) is quite challenging for in vivo retinal imaging. Indeed, high-resolution is normally achieved with adaptive optics (AO) and scanning methods, which reduce the useful FOV to about 0.5 mm x 0.5 mm. In this paper, we present a time-domain Full-Field OCT (FFOCT) system capable to generate high-speed (up to 300 Hz) and high-resolution cone mosaic images in the living human retina with a 1 mm x 1 mm FOV in a single shot, without the use of AO.
We developed a 3D retinal imaging system combining time-domain FFOCT for en face views with a spectral-domain scanning OCT for cross-sectional views. The SD-OCT is used to perform axial motion correction. Image acquisition was performed in a dark room, maximizing pupil dilation, while subjects were wearing their prescribed eyeglasses. Wide FOV was achieved by optically manipulating the FFOCT coherence gate geometry to match the retinal curvature.
Matching coherence gate geometry to retinal curvature enabled us to obtain, with good consistency and repeatability, photoreceptor mosaic images with a useful FOV of 1 mm x 1 mm, where cone mosaic at 1° was resolved. We show that, within this enlarged FOV, important photoreceptor-based biomarkers, such as distribution, density, and spacing, could be measured pointwise, and individual photoreceptors could be monitored in 4D (i.e. space and time). Finally, we compare our findings with AO-assisted ophthalmoscopes, highlighting the lower sensitivity to low-order ocular aberrations of the FFOCT in terms of resolution, thanks to the use of a spatially incoherent light source.
To the best of our knowledge, this is the first OCT system allying the following properties: i) micrometer resolution in all three dimensions over an en face FOV as large as 1-mm ii) fast acquisition rate of a given en face retinal plane (up to 300 Hz), iii) no optical nor digital aberration compensation other than prescribed eyeglasses, considerably simplifying the hardware and software complexity. The relative simplicity and low-cost of the FFOCT imaging technique compared to current AO-assisted ophthalmoscopes may pave the way towards the adoption of FFOCT as a routine clinical imaging system.
This is a 2020 ARVO Annual Meeting abstract.
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