Exploring Inner Choroidal Flow Deficits Across the Different Stages of Dry Age-related Macular Degeneration: Insights from Swept-Source OCT Angiography and Associations with Structural Biomarkers.

Abstract

Purpose : Inner choroidal flow deficit percentage (ICFD%) is a new metric to assess choriocapillaris perfusion using optical coherence tomography angiography (OCTA). Aim of this study is to establish a reference database for ICFD% for dry age-related macular degeneration (AMD) and explore the association with other imaging biomarkers.

Methods : This observational, cross-sectional study included dry AMD eyes (Beckman classification) with good-quality 6x6-mm swept-source OCTA (PLEX® Elite 9000; Carl Zeiss Meditec).
OCTA scans were processed on ARI Network with the Choriocapillaris Slab Imaging algorithm (v.0.2). 5-25-µm compensated angio images with Max Projection were imported in FIJI (NIH), and ICFD% was measured after binarization (Phansalkar method, r=15 px) in the central 6, 3, and 1 mm circles and ETDRS sectors. Additionally, (1) scans were graded for subretinal drusenoid deposits (SSD), (2) drusen volume in the central 3 mm was collected from PLEX® Elite software, (3) size of retinal pigment epithelium (RPE) atrophy was manually measured from the hypertransmission defects slab (RPE-RPE, 64-400 offset).
The relationship between ICFD%, AMD stage, and other biomarkers was assessed using non-parametric comparison tests and generalized linear mixed-effects models after nesting and adjusting for age.

Results : Overall, 270 eyes of 181 patients (median age 74, Female 76%) were included (70 early, 121 intermediate, 79 advanced dry AMD).
ICFD% were 19.7-22.0 for early, 24.3-27.7 for intermediate, and 29.5-32.4 for dry advanced AMD. ICFD% significantly increased with AMD stage severity, SDD presence, and greater RPE atrophy in all the analyzed regions (all p<0.05). On multivariate analysis, older age and more severe AMD stage were associated with greater ICFD% in all analyzed regions (all p<0.01). More extensive RPE atrophy was associated with greater ICFD% in the 6-mm circle and outer ETDRS sectors (all p<0.05).

Conclusions : This study establishes an initial reference database for ICFD% across dry AMD stages and reports associations with characteristic AMD imaging biomarkers. Our findings show that greater choriocapillaris flow deficits are seen with aging, more advanced AMD stage, and larger RPE atrophy. ICFD% is a promising OCTA biomarker for assessing the perfusion status of choriocapillaris in AMD.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.