A Comparative Study of Short-Term Vascular and Stromal Alterations of the Choroid Following Half-Fluence Photodynamic Therapy in Pachychoroid Neovasculopathy and Chronic Central Serous Chorioretinopathy.

Background: Central serous chorioretinopathy (CSCR) and pachychoroid neovasculopathy (PNV) are among the pachychoroid spectrum diseases (PSDs). Half-fluence photodynamic therapy (hf-PDT) is one of the effective treatment methods for both diseases. The aim of this study was to compare the effect of hf-PDT on the choroidal structure in CSCR and PNV. Methods: This study included 35 patients with chronic CSCR and 18 patients with PNV. The hf-PDT protocol was applied to all eyes. Before and 3 months after hf-PDT, enhanced-depth optical coherence tomography images were analyzed. The total choroidal area (CA), luminal area (LA), and stromal area (SA) were measured using ImageJ software. Results: Compared with baseline values, 3 months after hf-PDT, the mean CA reduced from 1.398 to 1.197 mm2 (p < 0.001) in the CSCR group and the total CA reduced from 1.050 to 1.000 mm2 (p < 0.021) in the PNV group. The mean percentage changes in CA, LA, and SA values were statistically higher in the chronic CSCR group (13.86%, 13.53%, and 14.11%, respectively) than those in the PNV group (4.61%, 4.02%, and 5.74%; p = 0.001, p = 0.002, and p = 0.031, respectively). Conclusion: CSCR and PNV are thought to be PSDs. However, they differ in choroidal morphological response after hf-PDT, which might be a result of the different structural components of the PNV lesions.