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.
Highlights
Detecting and assessing the surface of capillary non-perfusion areas is a critical prognostic factor in many retinal vascular diseases, especially in diabetic retinopathy and retinal vein occlusion[10,11,12,13]
The analysis was performed on a 22-mm horizontal band from the nasal to the temporal sector passing through the fovea and the lower part of the optic nerve head (ONH) and on a 22-mm vertical band from the superior to the inferior sector passing through the fovea
We took advantage of the high resolution provided by SS-OCTA at 100 KHz to explore the peripheral retinal circulation
Summary
Detecting and assessing the surface of capillary non-perfusion areas is a critical prognostic factor in many retinal vascular diseases, especially in diabetic retinopathy and retinal vein occlusion[10,11,12,13]. This objective has been partially met using ultra-widefield fluorescein angiography (FA), but its resolution in the periphery is insufficient to accurately measure capillary non-perfusion areas compared to WF-OCTA14. 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
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