OCTA Imaging Acquisition

12 x 12 mm and 15 x 9 mm scans and the wide-field montage OCTA scans consisting of five 12 x 12 mm scans or of two 15 x 9 mm scans, covering about 70 (2 x 15 x 9 mm)-90 (5 x 12 x 12 mm) degrees of posterior pole, were performed and generated using the Swept-source (SS)-OCT (PLEX Elite 9000; Carl Zeiss Meditec, Inc, Dublin, CA). The inbuilt segmentation algorithms were used to create the en-face SS-OCTA wide field slabs. The CC slab segmentation extended from 29 microns to 49 microns beneath the RPE and the choroidal slab segmentation extended from 64 microns to 115 microns below Bruch's membrane (14). Prior creating the montage scans, each individual 12 x 12 and 15 x 9 scan was checked by two trained ophthalmologists and OCTA experts (M.T. and M.R.M.) for alignment errors and artifacts. Minor alignment errors were manually corrected using the inbuilt software. In case of severe artifacts and alignment errors the patient was excluded.

CC and choroidal slabs of the wide-field montage OCTA images were examined for the presence of non-detectable flow signal and flow deficit (15). In order to allow an accurate quantitative lesion size comparison between OCTA and ICGA, respectively, only non-detectable flow signal areas of ≥1/4 optic nerve head (ONH) area of were considered and assessed (16).