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S. A. Burns, Z. Zhangyi, T. Y. P. Chui, H. Song, A. E. Elsner, V. E. Malinovsky; Imaging the Inner Retina Using Adaptive Optics. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4512. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To probe the structure of the inner retina using an Adaptive Optics SLO/OCT combination system. To better characterize the microstructures of the vasculature and nerve fiber layer.
An Adaptive Optics system using both SLO and OCT imaging modalities with an 840 nm (center wavelength) SLD as a light source was used to image the inner retina of four normal subjects. The wavefront of the eye was corrected using a Boston Micromachines MEMS deformable mirror and Shack Hartmann sensor operating in a closed loop at 8 Hz. A Badal optometer was used to correct .ammetropia, as well as to displace the plane of focus from the photoreceptors to the inner retinal layers. Imaging emphasized multiple 1.8 x 1.6 deg.loci, at 7 to 10 deg, in both the superior and inferior fields. The region of interest was guided by a simultaneous, large field SLO image, that permitted directing the high magnification imaging to selected arteries and veins for several deg across the retina, forming a large montage to compare to published histology at several magnifications.
Image quality was excellent. Small features down to 6 microns were reproducibly visualized over time. At arterio-venous (AV) crossings, there was an abrupt change in the appearance of the retina. Vessels were joined by a fibrous membrane, with fibers on the order of 3-8 microns, presumably related to the inclusion of the vein within the adventitial sheaths of the arteries. At the AV junctions, there was a marked decrease in the background structures, with a visible ring around the junction. Near the vessels there were sparse circular or annular white structures, approximately 20 microns in diameter. These lay along the surface of the nerve fiber layer as confirmed with AOOCT. These cells were deep to the peripapillary vasculature, which was readily imaged, and enhanced due to movement of cells within the capillaries.
Small structures in the inner retina are visualized in high contrast, and repeatably, using an AOSLO. The same instrument, by merely a change of focus, is used to locate outer retinal structures, such as photoreceptors. This system allows the rapid identification and localization of structures, including peripapillary capillaries, nerve fibers bundles in the nfl, nerve fibers as they cross the vasculature, and support structures of the vasculature. We can also repeatably image cellular structures along the surface of the retina, although the histological correlates are not yet known.
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