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Kaitlyn Sapoznik, Ting Luo, Raymond Luval Warner, Alberto De Castro, Lucie Sawides, Stephen A Burns; Enhanced imaging of retinal vessels using a configurable aperture AOSLO. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3434. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Multiply-scattered light retinal imaging enables visualization of retinal structures not apparent in confocal images. We tested the hypothesis that using a spatially programmable aperture could improve visualization of retinal features with an AOSLO.
A dual-beam AOSLO system was used to obtain confocal and multiply-scattered light images of the retinal vasculature in 5 normal subjects. The first multiply scattered light channel (810 nm) is obtained using an offset aperture. A second imaging channel (780 nm) generated three simultaneous images. The first was a confocal image and the remaining two multiply-scattered light channels were obtained by re-imaging the region outside the confocal aperture onto a micro-mirror array (TI-DLP 6500). MATLAB was used to program aperture shapes and display them on the array. The on-state of the array was reflected to one detector, the off state to another. We compared imaging with a split detection arrangement oriented at 0 and 45 degrees to a split annulus aperture (Fig. 1), rotated in 45 degree increments and also using different radii. Videos were captured for each condition.
Digital control of apertures allowed multiple comparisons within a single imaging session. Feature contrast depended systematically with aperture configuration. For instance as the inner radius of a split annulus was increased, vessel wall contrast decreased 96% in one subject. In all subjects at highest inner radius remaining contrast was almost entirely from moving red blood cells. Contrast between the vessel walls and adjacent retina varied with aperture type and angle (Fig. 1). Varying the rotation for split detection and split annular apertures changed the visibility of flow and structures orthogonal to the orientation. Split annuli provided excellent visibility of mural cells for both venules (Fig. 1B) and arterioles (Fig. 2).
Varying rotation of split detection and split annuli apertures enables enhanced visualization of the retinal vessel walls. The configurable aperture approach, which could be changed from frame to frame, should allow rapid imaging of retinal cellular features in a controlled manner.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Fig. 1. Aperture configuration impacts image contrast. Comparison of imaging using a split detector (A) and a split annulus (B). White rectangles indicate sample areas for contrast calculation. Note the inferior branch of the venule (3) wall structure is more apparent in B.
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