Retinal Ganglion Cell Layer Thickness and Local Visual Field Sensitivity in Glaucoma

Objective: To compare loss in sensitivity measured using standard automated perimetry (SAP) with local retinal ganglion cell layer (RGC) thickness measured using frequency-domain optical coherence tomography in the macula of patients with glaucoma. Methods: To compare corresponding locations of RGC thickness with total deviation (TD) of 10-2 SAP for 14 patients with glaucoma and 19 controls, an experienced operator hand-corrected automatic segmentation of the combined RGC and inner plexiform layer (RGC + IPL) of 128 horizontal B-scans. To account for displacement of the RGC bodies around the fovea, the location of the SAP test points was adjusted to correspond to the location of the RGC bodies rather than to the photoreceptors, based on published histological findings. For analysis, RGC + IPL thickness vs SAP (TD) data were grouped into 5 eccentricities, from 3.4 degrees to 9.7 degrees radius on the retina with respect to the fovea. Results: The RGC + IPL thickness correlated well with SAP loss within approximately 7.2 of the fovea (Spearman rho = 0.71-0.74). Agreement was worse (0.53-0.65) beyond 7.2 degrees, where the normal RGC layer is relatively thin. A linear model relating RGC + IPL thickness to linear SAP loss provided a reasonable fit for eccentricities within 7.2 degrees. Conclusion: In the central 7.2 degrees, local RGC + IPL thickness correlated well with local sensitivity loss in glaucoma when the data were adjusted for RGC displacement.