Vision process is ruled by several cells layers of the retina. Before reaching the photoreceptors, light entering the eye has to pass through a few hundreds of micrometers thick layer of ganglion and neurons cells. Macular degeneration is a non-curable disease of themacula occurring with age. This disease can be diagnosed at an early stage by imaging neuronal cells in the retina and observing their death chronically. These cells are phase objects locatedon a background that presents an absorption pattern and so difficult to see with standard imagingtechniques in vivo. Phase imaging methods usually need the illumination system to be on the opposite side of the sample with respect to theimaging system. This is a constraintand a challenge for phase imaging in-vivo. Recently, the possibility of performing phase contrast imaging from one side using properties of scattering media has been shown. This phase contrast imaging is based on the back illumination generated by the sample itself.
Here, we present a reflection phase imaging technique based on oblique back-illumination. The oblique back-illumination creates a dark field image of the sample. Generating asymmetric oblique illumination allows obtaining differential phase contrast image, which in turn can be processed to recover a quantitative phase image. In the case of the eye, a transcleral illumination can generate oblique incident light on the retina and the choroidal layer.The back reflected light is then collected by the eye lens to produce dark field image.
We show experimental results of retinal phase imagesin ex vivo samples of human and pig retina.
Timothé LaForest, Dino Carpentras, Laura Kowalczuk, Francine Behar-Cohen M.D., and Christophe Moser, "Quantitative phase imaging of retinal cells (Conference Presentation)," Proc. SPIE 10074, Quantitative Phase Imaging III, 1007419 (Presented at SPIE BiOS: January 31, 2017; Published: 24 April 2017); https://doi.org/10.1117/12.2251478.5380600151001.
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