Retinal Capillary Plexus Pattern and Density from Fovea to Periphery Measured in Healthy Eyes with Swept-Source Optical Coherence Tomography Angiography

Abstract

Optical coherence tomography angiography is evolving towards wider fields of view. As single widefield acquisitions have a lower resolution, preventing an accurate segmentation of vascular plexuses in the periphery, we examined the retinal vascularisation from the macula to the periphery in all retinal quadrants, using 3 × 3-mm volume scans, to obtain montages with sufficient image resolution up to 11 mm from the foveal centre. Images were qualitatively and quantitatively analysed, using C-and B-scan approaches to calculate the capillary density (CD) and the interplexus distance (IPD). three vascular plexuses (i.e., superficial vascular plexus: SVP, intermediate capillary plexus: ICP, and deep capillary plexus: DCP) were observed up to the mid-periphery in all sectors. The CD of the SVP decreased from about 5 mm of eccentricity, along with ganglion cell density decrease. The CD of the icp progressively decreased from the fovea towards the periphery, along with the retinal thinning and then vanished from 8 to 9 mm of eccentricity, becoming undetectable beyond. This ICP disappearance resulted in an increased IPD between the SVP and the DCP in an area known to be frequently affected by capillary drop-out in diabetic retinopathy. The DCP only showed a slightly decreased CD towards the retinal periphery.Thus, it becomes important to better know the morphology, distribution and density of the different capillary plexuses from the fovea to the periphery. However, although WF-OCTA provides an image of the whole retinal capillary network that is qualitatively better than FA images, the resolution and segmentation of each capillary plexus with wider scans (i.e., 12 × 12-mm C-scans) is not sufficient to reliably assess the capillary plexuses and measure the capillary density (CD) 17,18 .The aim of this study was to evaluate the normal retinal vascularisation from the fovea to the far periphery. To overcome some of the limitations of wider scans, montages of small-field (3 × 3-mm) OCTA C-scans were used to provide a better resolution and fewer segmentation artefacts. MethodsDemographics. This study, conducted in the

Optical Incoherence Tomography: a method to generate tomographic retinal cross-sections with non-interferometric adaptive optics ophthalmoscopes

“…4(b) and 5(b). All measured values, and the fact that the IVP is closer to DVP in Temporal position compared to Nasal, are consistent with in-vivo OCT angiography data in previous studies [24,28,29]. Full Z-stacks used to generate the OIT images of Figs.…”

“…4(g)). Figure 5 presents the same comparison and results but at 7 o Temporal, where NFL is less dense and all three expected vascular plexuses [28] are visible in the split-detection OIT. Table 1 gives the axial distance between consecutive plexuses measured through OIT crosssections of Figs.…”

“…By producing the OIT corresponding to a Z-stack of perfusion map images (Fig. 4(c)), we can deduce that these layers correspond to vascular plexuses, of which we expect there to be four at 7 o Nasal [24,28]. Using the split-detection OIT to precisely position the focal plane, we were able to extract perfusion maps of each of the four vascular plexuses (Fig.…”

Coherence gate shaping for wide field high-resolution in vivo retinal imaging with full-field OCT

“…Although FF-OCT axial resolution may be slightly poorer than AO-OCT [10], it has advantages of larger FOV, higher-frame rate and lower complexity and size, and is still able to resolve the photoreceptor interfaces such as IS/OS junction and cone outer segment tips. Moreover, the high temporal resolution of FF-OCT may play an important role to characterize the temporal behavior of retinal capillaries from different plexus [36,37] and the temporal dynamics of subcellular structures [27]. Finally, although FF-OCT is only weakly sensitive to low-order ocular aberrations in terms of resolution, aberrations still reduce the FF-OCT signal level [38].…”

Association of macular perfusion status with microvascular parameters up to the far periphery in diabetic retinopathy using multimodal imaging

“…Histological studies show basement membrane disorder of the small vessels, loss of pericytes and obliteration of the precapillary arterioles associated with retinal capillary atrophy, leading to local capillary and arteriolar occlusions [ 4 , 5 ]. These abnormalities cause circulatory disturbances primarily at the midperiphery due to distinct anatomical conditions of the intermediate capillary plexus (ICP), which gradually decreases from the fovea towards the periphery and becoming undetectable from 8 mm eccentricity potentially due to decreasing metabolic demand of the thinning retina [ 6 ]. The first occurrence of DR lesions have been reported to appear in the retinal periphery defined as the region outside the major vascular arcades and subdivided by the vortex vein ampulla into midperiphery and far periphery [ 3 , 7 , 8 ].…”