Purpose
This study demonstrates spatial and temporal relationships between the 2 processes of RMD, subretinal drusenoid deposits (SDD) and choroidal alterations, in early Age-Related Macular Degeneration (AMD).
Methods
33 eyes (26 subjects) with early AMD/no SDD (RMD-) and 18 eyes (16 subjects) with early AMD/SDD (RMD+) underwent enhanced depth imaging spectral domain optical coherence tomography (EDI SD-OCT) in the macula for choroidal thickness (CTh) measurements at 11 points per scan, 475 μm apart, in 5 horizontal B scans, 1 mm apart: a grid of 55 points. These 55 data points were treated as a cluster, to control for within-subject variation, in a generalized estimating equation model of CTh as a function of SDD status, age, gender, OD/OS, and fundus region. Subdividing the sample by total group median age (<=82 and >82 years) allowed analysis of the annual rate of CTh change in 4 groups (RMD+, <=82: 7/18; RMD+, >82: 11/18; RMD-, <=82: 21/33; RMD-, >82: 12/33).
Results
CTh was significantly reduced in the subfoveal region in RMD+ eyes compared to RMD- eyes (mean difference= - 12 μm, P=0.02), but not in the nasal or temporal regions. Among subjects <=82 years old, the overall mean CTh was significantly reduced in RMD+ eyes compared to RMD- eyes (mean difference= - 54 μm, P=0.012). Conversely, there was no significant difference in CTh in the older group (>=82 years) between RMD+ and RMD-. In the older age group, with each additional year of age, the choroids of RMD+ eyes got thicker (trend, 4.8 µm/year, p=0.33), while choroids of RMD- eyes got thinner (trend, -0.3 µm/year, p=0.39).
Conclusions
Choroidal alterations in RMD vary with age and fundus region. The choroid was thinner in RMD+ than RMD- eyes in the subfoveal region. Among subjects <=82 years old, the choroid was significantly thinner overall in RMD+ eyes, but not in older subjects, highlighting the role of age. In RMD+ eyes, CTh dynamics showed a trend to thinning before age 82, followed by thickening after this age, consistent with RMD-associated choroidal stromal fibrosis and thickening as a late development. RMD is a dynamic disease in 2 compartments, SDD in the subretinal space and pathology in the choroid, which must be studied together.