Early changes in choriocapillaris flow voids as an efficacy biomarker of photodynamic therapy in central serous chorioretinopathy

To assess the early changes produced in the choriocapillaris (CC) and choroidal vasculature using swept-source optical coherence tomography angiography (SS-OCTA) in patients with persistent central serous chorioretinopathy (CSCR) as predictors of the efficacy after photodynamic therapy (PDT). Prospective observational study in 52 eyes of 52 patients with persistent subretinal fluid (SRF). SS-OCTA scans of the 6 × 6 mm macular region were assessed before; 2–3 days, one month and three months after half-fluence PDT. Vessel occlusion in the CC and choroid was measured as flow signal voids (FSV). A 3.67 ± 4.12 and 2.76 ± 3.63 fold increase in CC and CH FSV, due to vessel occlusion, was observed at 2–3 days after PDT versus baseline. There was less SRF at 3 months in patients with an increase in FSV (≥1-fold) compared to those without this increase (<1-fold) after PDT ( p  ≤ 0.003). An association between the increase in CC and choroidal FSV at the early control (2–3 days) and the height of SRF at 1 month was found ( R =-0.405; p  = 0.002 and R =-0.356; p  = 0.008 respectively). In a multivariate model, the SRF at one month was not associated with age, gender, visual acuity, or FSV ( p  ≥ 0.288). At 3 months, flow restoration was achieved in the choroid versus the baseline ( p  = 0.619), but there was a persistent increase in the CC FSV ( p  = 0.008). Early vessel occlusion by OCTA after PDT in CSCR was associated with good treatment response. Therefore, an increase in FSV immediately after PDT could be a biomarker to predict SRF resorption.