The non-invasive measurement of cellular physiological responses to photostimulation in living retina may have significant clinical value and give new insight into the vision process. Optical coherence tomography (OCT) has been reported to detect suitable intrinsic optical signals (IOS) in retinal photoreceptor layers upon their stimulation. Commonly, changes in backscattering intensity were observed ex vivo and immobilized animals in vivo. However, in humans measurements were time-consuming and cumbersome. Promising results were achieved when observing phase signals to detect intrinsic optical signals. But to achieve sufficient phase stability to image an entire area of photoreceptors turned out to be challenging. Here, we report full-field swept-source OCT to be sufficiently stable to detect the phase signals after projecting a stimulation image onto the living human retina. We extracted time-courses and signal dependencies from the measured datasets. For long stimuli, we were even able to assign responses to single cones. This functional imaging of photoreceptor activity could potentially be used to detect loss of photoreceptor function prior to visible morphological changes, which is associated with numerous retinal diseases.
Dierck Hillmann, Hendrik Spahr, Clara Pfäffle, Helge M. Sudkamp, Gesa L. Franke, and Gereon Hüttmann, "Imaging of physiological responses to photostimulation in human photoreceptors with full-field swept-source OCT (Conference Presentation)," Proc. SPIE 10053, Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XXI, 100530G (Presented at SPIE BiOS: January 30, 2017; Published: 19 April 2017); https://doi.org/10.1117/12.2250872.5371723131001.
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