Abstract
Purpose :
To differentiate four-layered retinal vessel networks and clarify the morphologic features using high-resolution optical coherence tomography angiography (HR-OCTA).
Methods :
Ten healthy subjects (6 men and 4 women) without ocular
diseases were included. The mean age of the subjects was 30.7 ± 7.0 years.
For the right eye of each subject, a macular area of 4×4 mm2 (464×464 pixels)
was scanned 10 times using HR-OCTA (OCT-HS100, Canon), and the averaged OCTA image was created. Based on the clear decorrelation signals of blood flow, 4 individual vascular slabs were segmented, each of which was present in one of the retinal nerve fiber layer, ganglion cell layer (GCL), and top and bottom of the inner nuclear layer (INL). The qualitative features, quantitative vessel density (VD), and fractal dimension (FD) of each vascular slab were compared to those of superficial and deep capillary plexuses that were conventionally segmented at the default setting.
Results :
Macular HR-OCTA could differentiate four-layered vascular slabs that showed unique features in each layer. The first slab showed an intra-C-shaped radial peripapillary capillary network (RPCN), which was found to minimally communicate with macular retinal arteries and veins. The superficial capillary plexus by the default segmentation contained the RPCN and the capillaries at the top of the INL. Conversely, the GCL vascular slab isolated the RPCN and the parts of capillaries of the INL, which contributed to visualizing the capillary-free zone around retinal arteries, and lobular circulatory units composed of arterioles, capillaries, and venules. In the current segmentation, the foveal avascular zone was detected, not at the slab of GCL, but at the top of the INL. Capillaries at both the top and bottom of the INL showed vortex arrangements, and ascended to the venules in the GCL. However, the VD and FD of the capillaries at the bottom of the INL were significantly higher than those at the top of the INL (P=0.014, 0.002, respectively), and the vortex arrangement was more apparent. The VD and FD of the four vascular slabs increased according to the retinal depth (VD: 25.9%, 33.8%, 37.1%, 38.3%; FD: 1.49, 1.52, 1.59, 1.60).
Conclusions :
HR-OCTA can differentiate morphologic features of retinal microcirculation of the human macula.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.