Macular GCL vs. IPL Rates of Change in Eyes with Suspected and Established Glaucoma

Abstract

Purpose : Dendrite remodeling may occur in stressed or injured retinal ganglion cells (RGC) before apoptosis. Macular inner plexiform layer (IPL) thickness has been proposed as a biomarker for early glaucomatous damage. We compared ganglion cell layer (GCL) and IPL rates of change (RoC) in two patient cohorts with suspected and established glaucoma to test the hypothesis that RoC of IPL may be superior to GCL for detection of early glaucoma damage.

Methods : 64 eyes (46 patients) with suspected glaucoma (GS) and 112 eyes (112 patients) with moderate to severe visual field damage and ≥2 years of follow-up and ≥3 macular OCT scans were recruited. The GS cohort had suspicious optic discs with normal OCT retinal nerve fiber layer thickness at baseline. GCL and IPL measurements from the central 18° of the macula (36 superpixels, 3°×3° each) were exported. A Bayesian linear hierarchical model with random intercepts, slopes, and random variances was fitted to estimate GCL and IPL RoC at superpixels. RoC were normalized by dividing absolute rates by their SD. Normalized RoC and proportions of superpixels with significantly negative RoC for GCL and IPL were compared within the GS and glaucoma groups.

Results : The average (SD) baseline age, mean (SD) follow-up time, and average (SD) number of OCT scans were 61.3 (13.7) years, 3.5 (0.7) years and 4.2 (1.0) scans, respectively, in the GS group and 66.9 (8.5) years, 3.6 (0.4) years and 7.3 (1.1) scans in the glaucoma group. In the GS group, the mean normalized RoC (averaged across all superpixels) was faster for GCL than IPL (0.66 vs.0.32 SD unit per year). In 24 out of 36 superpixels, average GCL RoC was significantly negative while only 8 out of 36 superpixels showed significant negative IPL RoC (p=0.003)(Fig.1). In the glaucoma group, the mean normalized RoC was faster for IPL than GCL (0.46 vs.0.28 SD unit per year). 13 out of 36 and 23 out of 36 superpixels had significant negative RoC for GCL and IPL, respectively (p=0.006)(Fig.1).

Conclusions : GCL thickness is more likely to demonstrate significant negative slopes compared to IPL in very early stages of glaucoma. In contrast, in eyes with established glaucoma, the IPL change rates tended to provide more information(Fig.2). These results confirm our prior findings based on cross-sectional data. The sum of GCL and IPL thickness may provide a stronger signal to detect change in the macula.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

Proportions of significant negative RoC