Quantifying Macular Ganglion Cell Layer

OCT macular cube scans (61 B-scans covering an area of 30° × 25°) were acquired with Spectralis SD-OCT (Heidelberg Engineering, Heidelberg, Germany), as previously described.²⁶ (link)^,27 (link) Scans with significant artifacts or signal strength of lower than 15 dB were excluded. Scans were automatically segmented into each individual retinal layer using the HRA/Spectralis Viewing Module (Heidelberg Engineering). The GCL was reviewed (Fig. 1A) in all scans and manually corrected if necessary. GCL thickness was then extracted from across the macula as 64 measurements within an 8 × 8 grid centered on the fovea (each grid location covering 0.74 mm² [approximately 3° × 3°]; Fig. 1B). For scans where manual correction was not possible, grid locations were excluded from the analysis. If an eye had >10% of grid locations missing, the eye was excluded from the analysis.²⁷ (link)