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Masaharu Ishikura, Akihito Uji, Yuki Muraoka, Sotaro Ooto, Akitaka Tsujikawa; Visualization of Four-layered Retinal Vasculature: High-Resolution Optical Coherence Tomography Angiography Versus Non-Confocal Adaptive Optics Scanning Light Ophthalmoscopy. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4625. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Optical coherence tomography angiography (OCTA) can be used for visualization of the multiple capillary layers in the retina and choroid. However, due to its limited lateral resolution, background noise, and potential for artifacts, the detailed three-dimensional structure and the communication between these layers are difficult to visualize using OCTA. In this study, the morphology of the human retinal microvasculature was investigated using both high-resolution OCTA (HR-OCTA) and adaptive optics scanning light ophthalmoscopy (AOSLO).
Three healthy subjects with normal eyes (26-, 29-, and 43-years-old) were included. Macular cube scans (4 mm x 4 mm) were repeatedly acquired from the right eye of each subject using HR-OCTA (OCT-HS100, Canon), and ten sets of cube scans were averaged. Additionally, a 500 µm x 500 µm block within the HR-OCTA scanned area was repeatedly imaged using a prototype non-confocal AOSLO system.
Four-layered vascular slabs could be differentiated based on the morphological characteristics of macular HR-OCTA images (Muraoka et al. ARVO, 2018), i.e., the radial peripapillary capillary network , vascular slab of the ganglion cell layer (GCL), slab at the top of the inner nuclear layer (INL), and slab at bottom of the INL. Despite the lower axial resolution, four-layered vascular slabs were also identified in the AOSLO images under HR-OCTA guidance. Moreover, AOSLO images, which partially contain the adjacent vascular layer, were rather useful to observe the vessels axially linking the adjacent vascular layers, which were hardly detected by HR-OCTA (Figure 1, arrowheads). These vascular links were found throughout the four vascular layers. Capillaries at both the top and bottom of the INL showed a vortex arrangement in HR-OCTA as well as AOSLO. The direction of the moving blood cells confirmed by AOSLO videos demonstrated that the center of this arrangement was a venule that ascended and connected to the venule in the GCL. Although HR-OCTA could depict almost all capillaries imaged by AOSLO, the diameter of the capillary was significantly greater in HR-OCTA than in AOSLO (13.3 ± 1.79 μm vs 6.40 ± 1.01 μm, P <0.0001).
Combined imaging with HR-OCTA and AOSLO can further understanding of the three-dimensional structure of the retinal microvasculature.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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