Plex elite

On the same day, each patient underwent OCT and OCT-A with two different SS instruments, after pupil dilation. The same scanning protocol was used for image acquisition. The devices were prototype PLEX Elite 9000 (Carl Zeiss Meditec Inc., Dublin, California, USA) and DRI OCT-A Triton Plus (Topcon Medical Systems Europe, Milano, Italy). Zeiss PLEX Elite uses a 1,060 nm wavelength, with a scanning speed of 100,000 A-scans/second, and image processing is obtained through the so-called OCT-microangiography complex algorithm (OMAG) [23 (link), 24 (link)]. Topcon DRI-OCT uses a 1,050 nm wavelength, with a scanning speed of 100,000 A-scans/second and image processing relying on a motion contrast measure named OCT-A Ratio Analysis (OCTARA) [26 (link)]. The acquisition protocol performed included the following scans: a linear 12 mm high-definition B-scan centered on the fovea at 0°, OCT-A maps covering the central 3 × 3 mm and 6 × 6 mm macular area. All OCT-A images were carefully reviewed to check automatic segmentations of the superficial capillary plexus (SCP) and deep capillary plexus (DCP), and manual corrections were applied, when necessary, in order to ensure a correct segmentation. For PLEX Elite device, the projections' removal tool was applied for evaluation of DCP. Poor quality images and/or with artifacts were excluded from the analysis.

A PLEX Elite^® OCTA (Carl Zeiss Meditec, Dublin, CA, USA) was used to obtain en face images of the microvasculature around the fovea. The PLEX Elite^® is a swept-source (SS)-OCTA instrument that uses a swept laser source with a central wavelength of 1040 to 1060 nm (980–1120 nm full bandwidth) and operates at 100,000 A-scans per second. The eye with RRD was imaged using the 3 × 3 mm scan protocols centered on the fovea. All scans were reviewed by two graders (MS and TI). The VD of the DCP and CCP was measured in a 0.45 × 0.45 mm area centered at 1.2 mm from the fovea in a contralateral position to the fovea in the detached area and nondetached area (Figure 1). OCTA images of the DCP and CCP were binarized by the Otsu method [21 (link)]. The VD was calculated as the ratio of the area occupied by vessels divided by the total area of the binarized image. The ratio of VD ([detached area]/[nondetached area]) of the DCP and CCP was measured.

All eyes were imaged using UWF-CFP (Optos California; Optos, PLC, Dunfermline, Scotland; equipped with Optos V2 Vantage review Software) and spectral-domain OCT (Cirrus 5000 SD-OCT; Carl Zeiss Meditec Inc, Dublin, CA). In cases with uncertain NVs, UWF-FA (Optos) was performed. In addition, NPAs were assessed using OCTA (PlexElite, Carl Zeiss Meditec Inc) on a montage of five images of 12 mm ×12 mm (using the photomontage module of the device; theoretical image field of 24 mm × 24 mm).