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Timothé Laforest, Dino Carpentras, Mathieu Künzi, Laura Kowalczuk, Francine F Behar-Cohen, Christophe Moser; Phase imaging of retinal cells for clinical studies and diagnosis. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5876.
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© ARVO (1962-2015); The Authors (2016-present)
The evaluation and monitoring of cells health in the human retina is crucial for understanding retinal diseases. Towards this goal, a major challenge is to image retinal cells in human eyes in a non-invasive manner to, on one hand, detect abnormalities well before physiological and pathological changes occur and on another hand, monitor subclinical therapeutic effects to evaluate the efficacy of new drugs. However, in vivo imaging of many types of retinal cells is still extremely challenging despite the phenomenal advances in Optical Coherence Tomography (OCT) and Adaptive Optics systems. It stems from the fact that cell contrast in reflection is extremely low. Recent studies showed the possibility of imaging neuro-retinal cells in vivo using multiple OCT scans and requiring 10 minutes of acquisition.
Here, we report a major advance by proposing and demonstrating a radically different method than OCT to visualize retinal cells with high contrast and resolution in a much smaller acquisition time. The method uses a transscleral light beam which provides an oblique illumination of the retina. The light backscattered by the Retinal Pigment Epithelium (RPE) and Choroid layer is deviated by the neuronal cells before going out of the eye pupil.
Collecting this scattered light allows the reconstruction of phase images of the different cell layers. A single layer is reconstructed with full-field single shot images (no scanning), enabling a much faster acquisition rate. The method was validated ex vivo. The obtained results are in good agreement with images of retinal structures obtained with standard imaging techniques. The comparison with confocal microscopy shows an equivalent imaging quality without the cumbersome need to stain the sample.
Our method enables faster and less complex ex vivo studies of the retina compared to state of the art and opens new possibilities of in vivo imaging and diagnosis.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Figure 1. (a) The ex vivo imaging system. LEDs are used to provide oblique illumination of the sample. (b) Flat mounted retinal sample. The incoming light passes through the retina and it undergoes backscattering at the deeper layers. This backscattered light is used for illuminating the retina in transmission.
Figure 2. Comparison between phase and fluorescence imaging of the pericytes, shown with red triangles, and ganglions cells (red crosses).
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