Purpose
In non-advanced age-related macular degeneration (AMD), retinal thinning may occur over drusen, but it is unclear whether changes occur to the entire neurosensory retinal volume (NSRV) of the macula. We sought to compare NSRV of eyes with intermediate AMD vs. aged control eyes, and to correlate NSRV with future AMD progression.
Methods
Spectral domain optical coherence tomography (SDOCT) was obtained in 314 AMD eyes and 122 control eyes enrolled in the prospective observational AREDS2 Ancillary SDOCT Study. Semi-automated SDOCT segmentation of the neurosensory retina was performed from internal limiting membrane to outer border of the photoreceptor layer within a 5-mm diameter field centered on the fovea. Complete SDOCT segmentation and NSRV calculation were achieved in 269 AMD eyes and 118 control eyes at baseline. NSRV was compared between AMD and control eyes, and NSRV change was compared between baseline and year 1. In AMD eyes with noncentral geographic atrophy (GA), baseline NSRV was correlated to color fundus photography (CFP) measurement of GA area at years 2 and 4 of follow-up.
Results
Baseline NSRV (mean ± standard deviation) was 5.21 ±0.42 mm3 for 269 AMD eyes and 5.06 ±0.35 mm3 for 118 controls (p<0.001). Year 1 NSRV was 5.16 ±0.37 mm3 for 250 AMD eyes and 5.02 ±0.32 mm3 for 99 controls (p<0.001). In paired baseline and year 1 scans, NSRV decreased significantly for AMD (-0.05 ±0.15 mm3, p<0.001) and controls (-0.03 ±0.06 mm3, p<0.001). There was no significant difference between AMD and controls for NSRV change (p=0.15) or percent of eyes with decreased NSRV (70% AMD vs. 74% controls, p=0.59) from baseline to year 1. In eyes with noncentral GA based on CFP measurement, smaller baseline NSRV was correlated with greater total GA area at year 2 (n=23 eyes, Spearman rho=-0.76 p<0.001), greater total GA area at year 4 (n=30 eyes, Spearman rho=-0.52, p=0.003), and greater change in GA area from baseline to year 4 (Spearman rho=-0.54, p=0.003).
Conclusions
Total macular volume of the neurosensory retina was greater in eyes with intermediate AMD than controls, but the volume decreased in both groups over 1 year. Structural or inflammatory changes may induce macular thickening in some early categories of AMD. In intermediate AMD, NSRV was negatively correlated with future GA area; therefore, NSRV may serve as an SDOCT biomarker that predicts progression of GA size.