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

Purpose: 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).

Methods: 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).

Results: 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).

Conclusions: 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.