Background/aims To investigate the changes in the intrachoroidal structures after half-dose verteporfin photodynamic therapy (PDT) for central serous chorioretinopathy (CSC).

Methods Swept-source optical coherence tomography cross-sectional images of 22 eyes of 22 patients with CSC were retrospectively analysed by a manual delineation technique and binarisation method.

Results In the 22 eyes, the mean subfoveal choroidal thickness decreased from 412.9±112.9 μm at baseline to 340.0±111.0 μm at 3 months (p<0.0001). The mean thickness of the large choroidal vessel layer decreased from 368.7±112.7 μm at baseline to 292.2±118.0 μm at 3 months (p<0.0001), but the mean choriocapillaris-medium choroidal vessel layer thickness did not change from 44.2±29.2 μm at baseline to 47.8±25.7 μm at 3 months (p=0.85). Analyses of the binarised choroidal images showed that a 3 mm subfoveal choroidal area decreased from 1.141±0.290 mm² at baseline to 0.962±0.320 mm² at 3 months after PDT (p=0.0001). The mean luminal areas decreased from 0.826±0.246 mm² at baseline to 0.665±0.234 mm² at 3 months (p=0.0001), however, the mean stromal areas did not change from 0.315±0.066 mm² at baseline to 0.297±0.095 mm² at 3 months (p=0.60).

Conclusions Half-dose PDT reduces subfoveal choroidal thickness and alters the intrachoroidal structures in eyes with CSC.