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Muhammad Faizan Shirazi, Jordi Andilla, Marina Cunquero, Nicolas Lefaudeux, Danilo Andrade De Jesus, Luisa Sánchez Brea, Stefan Klein, Theo van Walsum, Kate Grieve, Michel Paques, Marie Elise Wistrup Torm, Michael Larsen, Pablo Loza-Alvarez, Xavier Levecq, Nicolas Chateau, Michael Pircher; Multi-modal and multi-scale retinal imaging with angiography. Invest. Ophthalmol. Vis. Sci. 2021;62(8):1761.
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© ARVO (1962-2015); The Authors (2016-present)
To demonstrate the results of a compact multi-modal and multi-scale retinal imaging instrument with angiographic functional extension and to explore its imaging performance.
The system has two imaging modes that are operated simultaneously: scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT). The field of view of both imaging modes can be changed between a standard large field-of-view mode and a high-resolution small field-of-view mode for cellular resolution imaging using adaptive optics (AO) correction of ocular aberrations. The SLO is operated at a central wavelength of 790 nm and records images at 13 Hz. The swept-source OCT is operated at 1060 nm with an A-scan rate of 200 kHz, which translates to a B-scan rate of 200 Hz. The AO correction is operated in closed loop at 10 Hz. Further, OCT angiography in large and small field-of-view modes can be achieved by acquiring 4 B-scans per position. An intensity based angiographic evaluation is used for the visualization of vessel networks. The dimensions of the entire instrument are 490 mm x 500 mm x 500 mm, including motorized translation stages that enable 3D tracking of the pupil position.
Images recorded in healthy volunteers with the large field-of-view mode (40 deg x 30 deg) show comparable quality as obtained with commercial systems. The attached figure shows representative images recorded with the instrument. The axial and lateral resolution is 7 µm and 4.4 µm respectively in AOOCT, while the lateral resolution is 3.3 µm in AOSLO. Images recorded with the high resolution AO-SLO mode show individual cone photoreceptors at half-degree from fovea and beyond. The high resolution of the OCT allows tomographic and en-face views of individual photoreceptors, discrimination between cone and rod end tip layers, and visualization of the Henle fiber layer border. The angiographic evaluation shows the vessel network and choriocapillaris in both large and small fields of view.
The combination of OCT and AO improves the lateral resolution, thereby enhancing the visualization of individual photoreceptors. The application of OCT angiography further enhances the appearance of the capillaries, e.g. their thickness in the en-face AOOCTA images. This multi-modal and multi-scale approach allows for a rapid identification of regions of interest in the large field-of-view mode and for a more detailed analysis in the high-resolution mode.
This is a 2021 ARVO Annual Meeting abstract.
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