Spectral Domain OCT for Retinal Layer Evaluation

Retinal imaging was performed with spectral domain OCT (Cirrus HD-OCT, Model 5000, software version 11.5; Carl Zeiss Meditec, Dublin, CA), as previously described.¹⁶ In brief, peripapillary and macular data were obtained using the Optic Disc Cube 200 × 200 protocol and Macular Cube 512 × 128 protocol, respectively. Scans with signal strength < 7/10 or with artifact were excluded, in accordance with OSCAR-IB criteria.¹⁷ Peripapillary retinal nerve fiber layer (pRNFL) thicknesses were derived using the conventional Cirrus HD-OCT software, as described elsewhere.¹⁶ A previously described segmentation algorithm was used for the generation of the thickness values for the rest of the retinal layers (macular ganglion cell layer/inner plexiform layer [GCIPL], inner nuclear layer [INL], and outer nuclear layer [ONL]).^{18 (link)} In more detail, average thicknesses of the GCIPL, INL and ONL were calculated within an annulus, centered on the fovea, with an inner radius of 0.5 mm and an outer radius of 2.5 mm. Macular cube scans and segmentations were manually reviewed and scans with macular pathology or segmentation errors/failure were excluded. OCT results are reported in this manuscript in concordance with APOSTEL guidelines.^{19 (link)}