Binarization Parameters Affect Quantitative Choriocapillaris Biomarkers Derived from Optical Coherence Tomography Angiography

Background/Objectives: Quantitative choriocapillaris biomarkers derived from optical coherence tomography angiography (OCTA) depend on binarization settings. We assessed Phansalkar parameters using chronological age as an exploratory physiological reference. Methods: Seventy participants (70 eyes) in three age groups (22–40, 41–60, and 61–83 years) underwent swept-source OCTA. In Fiji, the window radius (R = 2–6 pixels) was varied at k = 0.25 and r = 0.50; 24 k–r combinations were subsequently examined at R = 3. Age-group effects were evaluated using ANOVA, η2, false discovery rate (FDR) correction, and permutation max-statistic testing. Results: Across radii, only large flow-deficit counts (FDN5000 and FDN10000) consistently differed between age groups, peaking in middle age. Among the five radii, η2 was largest at R = 4 for FDN5000 (0.164) and at R = 3 for FDN10000 (0.261). The common working set (R = 3, k = 0.25, r = 0.50) maximized the mean η2 of both counts. At this setting, FDN10000 remained significant after family-wise correction (p = 0.001), whereas FDN5000 did not (p = 0.060). Conclusions: Parameter choice affects choriocapillaris quantification. The identified setting is an exploratory, protocol-specific candidate and requires external validation.