Full-field OCT systems and the use of adaptive optics have enabled high resolution, functional OCT imaging of photoreceptor cells. However, currently the technologies are limited to experimental systems. For clinical translation, clinical grade devices are needed with sufficient resolution as well as phase stability. In this talk it is shown that a slightly modified Spectralis OCT can resolve single photoreceptor cells. Furthermore, algorithms for the correction of motion induced artifacts will be introduced and discussed, as well as approaches for correcting for the respective phase errors in scanning OCT.
We report on new findings to which the observation of vascular dynamics using full-field swept-source OCT with a large field of view has led. In addition to the pulsatile expansions already known from previous measurements, pulsatile contractions of the retina were observed. These may be explained by a longitudinal expansion of retinal arteries. The motion of vessels is actually much more irregular than previously assumed, which renders the determination of pulse wave velocities challenging. Whether these irregularities and their transmission to the tissue can be associated with a clinically relevant biomechanical parameter needs to be clarified by further investigations.
Computational adaptive optics (CAO) is emerging as an attractive alternative to hardware-based solutions for diffraction-limited optical coherence tomography, e.g., of the human retina. Still, to become a reliable and robust solution, many challenges need to be solved. Here, we present CAO based on multiple randomized sub-apertures in combination with suitable filtering to remove disturbing artifacts. We show that this approach can reliably detect aberrations, and we compare results to other algorithms, such as optimization of imaging quality. We also demonstrate that the filtering of reflecting image structures is essential for a robust determination of aberrations.
Non-invasive functional retinal imaging in humans is of tremendous interest. By using phase-sensitive full-field swept-source OCT (FF-SS-OCT) we demonstrated simultaneous quantitative imaging of the optical activation in the photoreceptor and ganglion/inner plexiform layer. Since the signals from the ganglion cells layer are ten-fold smaller than those from the photoreceptor cells a new algorithms for suppression of motion artifacts and pulsatile blood flow in the retinal vessels is important. With improved data evaluation we simultaneously measured the activation of photoreceptors and ganglion/inner plexiform with high quality and were able to analyze the spatial and temporal response of cells in the ganglion/inner plexiform over more than 10 seconds.
Using phase-sensitive full-field swept-source optical coherence tomography we already showed that morphological changes in the photoreceptor outer segments are detectable. Those signals manifest themselves in an elongation of the optical path length. Using improved post.processing we report on progress in detecting signals in the neuronal layers of the human retina. The spatially resolved signals show a characteristic time course and by combining these with simultaneous measurements of the photoreceptors we were able to generate a wiring map of the neuronal retina.
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