Changes in choriocapillaris blood flow following half-fluence, full-dose photodynamic therapy (PDT) and half-fluence, half-dose PDT in patients with central serous chorioretinopathy: A quantitative analysis of early post-treatment alterations

Purpose: To investigate temporal changes in the choriocapillaris (CC) and the effects of varying laser energies using optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) in central serous chorioretinopathy (CSC) treated with photodynamic therapy (PDT). Method: Medical records of CSC patients who underwent PDT were retrospectively reviewed. Swept-source OCT and OCTA were performed prior to PDT (baseline), at 1 h, 1month and 4months post-PDT. For quantitative assessment, CC flow void was measured using the Phansalkar threshold method. Subjects were categorized into two groups. The HH-group was defined as eyes that received half-fluence, half-dose PDT, and the HF-group included eyes that underwent half-fluence, full-dose PDT. Results: The final analysis included 35eyes from 33patients. Of these, 10eyes were included in the HH group and 25eyes were assigned to the HF group. In the HF group, parameters associated with flow void area (total, average and percent area), except for CC count, exhibited a significant increase within 1 h after PDT compared to baseline, followed by a significant decrease at 1month (p < 0.05). By contrast, CC void count significantly declined 1 h post-treatment (p < 0.05) and returned to baseline levels at 1month. In the HH group, similar trends were observed without statistical significance. Conclusion: Short-term alterations in choriocapillaris flow void parameters appear to reflect the initial mechanism of PDT in CSC. Compared to the HH group, the significant vascular changes observed in the HF group suggest that vascular remodeling effects may differ depending on the PDT energy concentration used. This difference in vascular response could explain the lower recurrence rate observed in the HF group, indicating potential clinical advantages of half-fluence and full-dose PDT compared to half-fluence and half-dose PDT in CSC management.