Association between choroidal structure and retinal fluid location in type 1 neovascular age-related macular degeneration.

OBJECTIVES: To correlate choroidal structure parameters with the presence and amount of subretinal fluid (SRF) and intraretinal fluid (IRF) in treatment-naïve neovascular age-related macular degeneration (nAMD) patients with type 1 macular neovascularisation (MNV). METHODS: A retrospective study reviewed clinical records of 96 patients diagnosed with nAMD between 2015 and 2022. Optical coherence tomography (OCT) scans were analysed for choroidal thickness, choroidal vascularity index (CVI), and large choroidal vessel index (LCVI) using ImageJ software with automated binarisation. SRF was manually quantified using embedded OCT tools, and IRF volume was measured using an artificial intelligence-based platform. Patients with type 1 MNV (n = 56) were included for fluid-choroidal correlations. Statistical analyses included t-tests, Mann-Whitney U tests, and Spearman correlations (p < 0.05). RESULTS: In type 1 MNV eyes, SRF presence was associated with greater choroidal thickness (p = 0.03), and SRF area correlated positively with choroidal thickness (p = 0.02) and foveal LCVI (p = 0.004). Maximum SRF height correlated with foveal LCVI (p = 0.007). IRF presence was linked to reduced choroidal thickness (p = 0.0008), and IRF volume inversely correlated with choroidal thickness (p = 0.01) and macular LCVI (p = 0.002). No significant choroidal changes were observed pre-MNV or compared to fellow eyes. CONCLUSIONS: In treatment-naïve type 1 MNV, choroidal thickness and LCVI exhibit opposite associations with subretinal and intraretinal fluid, emphasising distinct pathophysiological mechanisms: choroidal venous overload may be associated with SRF accumulation, while choroidal thinning may be implicated in IRF formation. These findings may help generate hypothesis regarding variability in anti-VEGF treatment response and suggest that choroidal characteristics warrant further investigation as potential biomarkers for future individualised management strategies.