Choriocapillaris Flow and Retinal Vascular Fractal Dimension in Dry Age-Related Macular Degeneration

Background/Objective: To evaluate the association between optical coherence tomography angiography (OCTA)-derived choriocapillaris flow (CCflow), retinal vascular fractal dimension (FD), and drusen burden in eyes with dry age-related macular degeneration (AMD). Methods: This retrospective study included 113 eyes from 73 patients with dry AMD. Eyes were classified into large and small drusen groups based on median drusen area. OCTA-derived CCflow and FD indices of the superficial and deep capillary plexuses were analyzed. Patient-level clustered analyses were performed using linear mixed-effects and generalized estimating equation models to account for inter-eye correlation. Results: Eyes with large drusen showed significantly lower CCflow compared with those with small drusen (p < 0.001), whereas FDsup did not differ between groups, and FDdeep demonstrated only a near-significant trend toward higher values. CCflow was moderately and negatively correlated with drusen area (ρ = -0.452, p < 0.001), whereas FDdeep showed no significant correlation in unadjusted analyses (ρ = 0.137, p = 0.148). In patient-level age-adjusted multivariable models accounting for inter-eye dependency, CCflow remained independently associated with drusen burden, while FDdeep demonstrated an independent association only after adjustment for age. Conclusions: Reduced CCflow is independently associated with increased drusen burden in dry AMD. FD metrics provide complementary descriptive information regarding microvascular remodeling but do not function as independent biomarkers. CCflow may serve as a robust quantitative indicator of early choroidal compromise in dry AMD.