Correlation of retino-choroidal thickness and vascular metrics with drusen volume as a severity marker of age-related macular degeneration.

Objective: To assess retinal vascular perfusion and choroidal vascularity biomarkers correlated with drusen volume and severity of age-related macular degeneration (AMD).

Methods: Patients underwent swept-source optical coherence tomography angiography (SS-OCTA) (PlexElite-9000). Eyes with geographic atrophy or neovascular AMD were excluded. Retinal thickness, retinal perfusion including superficial (SCP) and deep capillary plexuses (DCP), foveal avascular zone (FAZ), drusen volume, choroidal thickness (ChT) and choroidal vascularity index (CVI) were assessed through the Advanced Research and Innovation Network. Linear mixed model and Spearman test were used for statistical analysis.

Results: We assessed 81 eyes from 57 subjects (34 early-stage, 47 intermediate-stage AMD). The mean age was 74.95 ± 8.79 years. The mean LogMar visual acuity (VA) was 0.16 ± 0.18 (early-stage: 0.12 ± 0.17, intermediate-stage: 0.19 ± 0.18, P = 0.122). Between early and intermediate AMD, no significant differences were seen in SCP and DCP vascular perfusion (P = 0.368, 0.859, respectively), FAZ (p = 0.836) and retinal thickness within the 6-mm area (P = 0.680). Drusen volume showed a significant difference (early-stage: 0.0706 ± 0.1272, intermediate-stage: 0.2102 ± 0.2211mm3, P < 0.01). Intermediate-stage AMD had significantly lower mean ChT (266.40 ± 115.55 vs. 204.97 ± 70.69 µm, P = 0.038) and CVI (0.605 ± 0.021 vs. 0.591 ± 0.015, P = 0.004) within the 5-mm area. Drusen volume was negatively correlated with ChT (r = -0.198, P = 0.017) and CVI (r = -0.209, P = 0.029). No significant correlation was found between drusen volume and VA (r = 0.051, P = 0.143), retinal thickness (-0.03, P = 0.393), FAZ (r = -0.023, P = 0.150), SCP (r = -0.011, P = 0.307), and DCP (r = -0.022, P = 0.190).

Conclusions: Drusen volume, a key AMD severity marker, correlates more strongly with choroidal parameters like ChT and CVI than retinal thickness and perfusion. It may serve as a biomarker for dry AMD severity, with choroidal biomarkers showing earlier disease changes.