Assessment of choriocapillary blood flow changes in response to half-dose photodynamic therapy in chronic central serous chorioretinopathy using optical coherence tomography angiography

BACKGROUND: Optical coherence tomography angiography (OCTA) is a newly developed imaging quantitative technique for analysis of choriocapillaris (CC) flow changes, thereby exploring the pathological mechanism of chronic central serous chorioretinopathy (CCSC) and the therapeutic effects of photodynamic therapy (PDT). In this study, we sought to quantify the blood flow changes in CC of CCSC patients receiving half-dose PDT using OCTA. METHODS: A total of 28 affected eyes and 24 unaffected eyes of 26 CCSC patients receiving half-dose PDT, and 40 eyes of 20 healthy gender- and age-matched subjects were retrospectively enrolled in this study. The proportion of total areas of flow signal voids (FSV, %) in CC level of OCTA was assessed in both eyes of the CCSC patients at baseline and repeated in multiple sections at 1-week, 1-month, 3-month and 6-month intervals after PDT. In addition, the CC patterns in response to PDT at early stage and the subsequent morphologic changes were qualitatively documented using OCTA. RESULTS: For affected eyes, FSV at 6-m follow-up was significantly lower than that at 1-m follow-up (p = 0.036). When compared to normal control eyes, FSV in affected eyes was significantly higher at 1-m, 3-m and 6-m follow-up (p < 0.05 for all), and FSV in unaffected eyes was significantly higher at baseline, 1-w, 1-m and 3-m follow-up (p < 0.05 for all). Three CC patterns of early response to PDT were identified, including signs of recovery with more even flow signals, transient appearance of worse ischemia and secondary neovascularization within CC level. CONCLUSION: Abnormal CC flow attenuation remains in completely resolved eyes of CCSC patients treated with half-dose PDT.