Longitudinal Analysis of the Choriocapillaris Using Optical Coherence Tomography Angiography Reveals Subretinal Fluid as a Substantial Confounder in Patients with Acute Central Serous Chorioretinopathy

Introduction To describe the influence of subretinal fluid (SRF) in analysis of the flow signal from the choriocapillaris (CC) via optical coherence tomography angiography (OCTA) in patients with acute central serous chorioretinopathy (CSC). Methods Observational, longitudinal, cross-sectional case-control study. Twenty-three eyes of 22 patients with acute CSC were compared with 20 eyes of 20 healthy controls. OCTA images (AngioPlex (R), Zeiss) were recorded at baseline and follow-up examination and automatically quantified using an image-processing algorithm. Abnormal CC decorrelation signals (increased and decreased flow, IF and DF) were quantified using a custom image-processing algorithm. To analyze the spatial correlation between SRF and OCTA, CC signal heat-map images containing macular thickness information were used. Results Choriocapillaris flow alterations were significantly more pronounced at baseline than at follow-up examination in patients with acute CSC and resolving SRF (IF: p < 0.002; DF: p < 0.003). The extent of SRF correlated significantly with the abnormal CC decorrelation signals when comparing baseline with follow-up examinations (IF: rho = 0.56, p < 0.005; DF: rho = 0.64, p < 0.001). In particular, the reduced OCTA flow signal in the area occupied by SRF at baseline disappeared at follow-up examination (p < 0.02). In comparison with controls, CSC patients with complete resorption of SRF continued to show a reduced OCTA flow signal in the CC (p < 0.008). Conclusions The temporospatial association between SRF and reduced OCTA signal from the CC demonstrates that fluid might be a significant confounder for OCTA analysis in patients with CSC. CSC patients with complete absorption of the SRF at follow-up, however, show persistently reduced CC flow signals.