Comparison of Retinal Nerve Fiber Layer and Ganglion Cell Complex Rates of Change in Patients With Moderate to Advanced Glaucoma

Abstract

PurposeTo compare ganglion cell complex (GCC) and retinal nerve fiber layer (RNFL) rates of change (RoC) in eyes with central or moderate to advanced glaucoma. DesignProspective cohort study. Participants918 matched macular and RNFL OCT scan pairs from 109 eyes (109 patients) enrolled in the Advanced Glaucoma Progression Study with ≥2 years of follow-up and ≥4 OCT scans. MethodsWe exported GCC and RNFL thickness measurements in 49 central macular superpixels and 12 RNFL clock-hour sectors, respectively. We applied our latest Bayesian hierarchical longitudinal model to estimate population and subject-specific baseline thickness (intercepts) and rates of change (RoC) in macular superpixels and RNFL sectors. Global RNFL and GCC RoC were analyzed in a single bivariate longitudinal model to properly compare them accounting for the correlation between their RoC. Main Outcome MeasuresProportion of significant negative (deteriorating) and positive (improving) RoC expressed in μm/year. Standardized RoC were calculated by dividing RoC by the corresponding population SD. Analyses were repeated in eyes with visual field mean deviation (MD) ≤–6 and >–6 dB. ResultsAverage (SD) 24-2 visual field MD and follow-up length were –8.6 (6.3) dB and 4.2 (0.5) years, respectively. Global RNFL RoC (–0.70 µm/year) were faster than GCC (–0.44 µm/year) (p<.001); corresponding normalized RoC were not significantly different (p=0.052). In bivariate analysis, patients with a significant negative global RNFL RoC (n=63, 57%) or GCC (n=56, 51%) frequently did so for both outcomes (n=49, 45%). The average proportion of significantly decreasing RNFL sectors within an eye was 30.7% in eyes with MD >–6 dB compared to 20.5% in those with MD ≤–6 dB (p=0.014); the proportions for GCC superpixels were 21.1% vs. 18.7%, respectively (p=0.63). ConclusionsBoth GCC and RNFL measures can detect structural progression in glaucoma patients with central damage or moderate to advanced glaucoma. The clinical utility of RNFL imaging decreases with worsening severity of glaucoma.