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Shaohua Pi, Xiang Wei, William Cepurna, Qisheng You, David Huang, John Morrison, Yali Jia; Rodent retinal circulation organization and location revealed by visible light OCT. Invest. Ophthalmol. Vis. Sci. 2019;60(11):007.
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To investigate the retinal circulation organization in rats using visible-light optical coherence tomography (vis-OCT).
Eight Brown Norway rat retinas were imaged with a 1.7-µm axial resolution, 50 kHz sampling rate, fiber-based vis-OCT system centered at 560 nm. Rats were anesthetized with 2.5 % isoflurane and 100% oxygen. Volumetric scans consisting of 512×3×512 A-lines covering a 2×2 mm2 area were acquired adjacent to the optic disc and in the periphery. OCT angiography was obtained by split-spectrum amplitude-decorrelation angiography (SSADA). Oxygen saturation in major retinal vessels was measured by automated spectroscopic retinal oximetry, taking advantage of the high absorption contrast of oxy- and deoxy- hemoglobin in the visible light band. Retinal layers (Fig. 1A) were segmented for projecting the en face images of the three vascular/capillary plexuses (SVP: superficial vascular plexus, ICP: intermediate capillary plexus, DCP: deep capillary plexus. Fig. 1B-D), as well as structures for the whole retina (Fig. 1E) and nerve fiber layer (NFL, Fig. 1G). Arteriovenous identification of all vessels were confirmed by measured oxygen saturation (Fig. 1E).
Oxygen saturation of 93% was used as a threshold to differentiate arteries from veins, based on prior observations. Arterioles were found predominantly in the SVP (Fig. 1B), whereas veins tended to drain blood from the DCP (Fig. 1D). Since inter-plexus capillaries are perpendicular to retinal layers and have greater absorption length along the light illumination direction, they appeared as dark spots on structural en face OCT (Fig. 1E), in contrast to neighboring capillaries. Inter-plexus capillaries were further validated by examining corresponding positions through the presence of capillaries in more than two plexuses in the overlaid en face angiograms of three vascular/capillary plexuses (Fig. 1F). The inter-plexus capillaries were found at capillaries end in SVP, as well as at some bifurcations,. Moreover, the capillary beds of the SVP were clearly visualized anterior to the nerve fiber bundles in the NFL slab en face image (Fig. 1G), with inter-plexus capillaries penetrating the NFL and connecting with the ICP and DCP.
The detailed retinal circulation organization, including the spatial distribution, inter-plexus capillary identification, and the relative position to the nerve fiber layer can be revealed by vis-OCT.
This abstract was presented at the 2019 ARVO Imaging in the Eye Conference, held in Vancouver, Canada, April 26-27, 2019.
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