Choriocapillaris impairment in dry AMD: insights from swept-source OCT angiography and associations with structural biomarkers.

AIMS To assess choriocapillaris flow deficit percentage (CCFD%) across stages of dry age-related macular degeneration (AMD) using swept-source optical coherence tomography angiography (SS-OCTA). METHODS This cross-sectional, observational study included 270 eyes (182 patients), classified as early (70 eyes), intermediate (121 eyes) and geographic atrophy (GA, 79 eyes).Participants underwent a complete examination including macular 6×6 mm SS-OCTA scans (PLEX Elite 9000). Scans were reviewed and analysed for subretinal drusenoid deposits (SDDs), retinal pigment epithelium (RPE) atrophy size, incomplete RPE and outer retinal atrophy (iRORA) and drusen volume (3 mm). CCFD% was calculated after compensation and binarisation using Phansalkar's method (r=4-15 pixels) in various early treatment for diabetic retinopathy study sectors. Linear mixed-effects models adjusted for age evaluated associations with AMD stages and other imaging biomarkers. RESULTS CCFD% progressively increased with advancing dry AMD stages. Intermediate AMD eyes showed higher CCFD% than early AMD ones across all regions (p<0.001). GA eyes exhibited significantly higher CCFD% compared with early (p<0.001) and intermediate AMD eyes (p<0.001).SDDs were significantly associated with higher CCFD% in early (p<0.01) and intermediate AMD (p<0.05) for almost all regions examined, but not in GA (p>0.05). iRORA presence in iAMD and larger RPE atrophy in GA correlated with increased CCFD% (p<0.001). CONCLUSIONS This study provides a comprehensive reference database for CCFD% across the stages of dry AMD using SS-OCTA. CCFD% increased with AMD severity, iRORA, SDDs, particularly in early and intermediate stages, and RPE atrophy size. Our findings support CCFD% as a valuable biomarker for clinical and research applications, warranting longitudinal studies to validate its prognostic value.