Anatomy of the Macular Ganglion Cell Layer Plexus on Projection-Resolved Optical Coherence Tomographic Angiography

The purpose of this study was to characterize the central macular ganglion cell layer plexus (GCLP) boundaries using projection-resolved optical coherence tomographic angiography (PR-OCTA) in healthy eyes.

Participants were scanned using a commercial OCTA system (Avanti; Optovue/Visionix Inc., Fremont, CA, USA) in a 6 × 6-mm area centered on foveal fixation.PR-OCTA algorithm was used to remove flow projection artifacts. The anterior GCLP boundary was marked at the nerve fiber layer (NFL)/ganglion cell layer (GCL) junction, and the posterior boundary with the intermediate capillaries plexuses (ICPs) was determined by searching the ganglion cell and inner plexiform layer (GCIPL) slab for the watershed depth with minimum vessel density (VD). The foveal avascular zone (FAZ) within a 1-mm diameter circle was excluded from the analysis because the retinal plexuses merge near the FAZ. A polynomial fit was used to model the relationship between VD and depth.

Thirty-eight eyes of 38 healthy participants (79% female subjects) were enrolled. The mean age and standard deviation were 59.6 ± 10.7 years. The watershed between the GCLP and ICP was located at 75% depth within the GCIPL throughout the macula. Analysis of macular sectors on a polar grid showed that GCLP VD was correlated with NFL, GCIPL, and macular ganglion cell complex (GCC) thicknesses (R2 = 0.26, 0.15, and 0.73, respectively, P < 0.01 for all). The correlation was significantly stronger for GCC.

We defined the anatomic GCLP slab in the macula on PR-OCTA, which is the anterior 75% of the combined GCIPL. Its density correlates best with GCC, which also contains the NFL, suggesting that it also supplies at least the posterior aspect of the NFL.

Mapping macular GCLP holds promise for evaluating perfusion, particularly in conditions such as glaucoma and optic neuropathies.