OCT examination was performed using a SD-OCT (Spectralis, Heidelberg Engineering, Heidelberg, Germany) with automatic real time (ART) function for image averaging as described before (35 (link)). Data are reported for peripapillary retinal nerve fiber layer thickness (pRNFL) to assess axonal degeneration, volume of combined ganglion cell and inner plexiform layer (GCIPL = GCL + IPL) as marker for neuronal degeneration, and for inner nuclear layer (INL). Macular layers were calculated for a 3 mm diameter cylinder around the fovea from a macular volume scan (20° x 20°, 25 vertical B-scans, ART ≤ 49). The pRNFL was measured with activated eye tracker using 3.4 mm ring scans around the optic nerve (12°, 1536 A-scans, ART ≤100). Segmentation of all layers was performed semi-automatically using software provided by the OCT manufacturer (Eye Explorer 1.9.10.0 with viewing module 6.3.4.0, Heidelberg Engineering, Heidelberg, Germany). All scans were checked for sufficient quality and segmentation errors and corrected, if necessary. OCT data are reported according to the APOSTEL (2.0) and OSCAR-Ib recommendations (51 (link)–53 (link)). Both eyes of each subject were included in subsequent analysis as statistically dependent duplicates.
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