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Michael Pircher, Franz Felberer, Matthias Rechenmacher, Richard Haindl, Bernhard Baumann, Christoph K Hitzenberger; Adaptive optics SLO/OCT for visualizing retinal vasculature . Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5888.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the capability of our previously developed adaptive optics scanning laser ophthalmoscope / optical coherence tomography (AO-SLO/OCT) instrument for visualizing retinal vasculature on a cellular level.<br />
The SLO/OCT instrument records both imaging modalities simultaneously and is operated at frame rates between 10 and 40 fps. The field of view of the system can be varied between 1° x 1° and 4°x4°. The small field of view allows for an optimum adaptive optics correction and high resolution imaging. The larger field of view is used to generate overview images of the retina that enable an easy determination of the imaged location. A typical measurement takes several seconds. The en-face OCT technique provides two different operating modes. In the first mode, a 3D volume scan of the retina is recorded. Since the system is equipped with a dynamic focus scheme, an entirely sharp 3D volume can be recorded. In the second mode, the coherence plane and the focus plane can be set into a layer of interest (such as a layer containing a vessel) and several en-face OCT images of this layer are recorded with high speed. This enables the visualization of dynamic processes such as blood flow and frame averaging (similar to AO-SLO instruments) in order to increase the signal to noise ratio. Axial eye motion is compensated using active axial eye tracking and transverse motion is corrected in a post processing step.
Retinal blood flow on a cellular level was visualized using this technology. For larger vessels the coherence gate was set at different locations (anterior vessel wall, center part of vessel, posterior vessel wall) within the tissue enabling the visualization of different structures. The en-face OCT images show subtle details such as individual erythrocytes or vessel walls. Frame averaging enabled the visualization of different blood streams within a vessel. In addition new structures within the surrounding tissue of the vessels were found.<br />
The AO-SLO/OCT instrument is well suited to study dynamic processes such as blood flow on a cellular level. The high depth resolution provided by OCT enables a clear separation between different structures of the retina. The overview images and the 3D information that can be recorded by the same instrument allow an exact localization of the imaged region.<br />
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