We thank Kucukevcilioglu and associates for their comments about our article. In our study, we investigated long-term changes in subfoveal choroidal thickness following photodynamic therapy (PDT) in chronic central serous chorioretinopathy (CSC) patients. We found that the degree of choroidal thinning following PDT reflects the treatment efficacy and may help predict long-term recurrence. Unlike central macular thickness, which remained stable after resolution of subretinal or intraretinal fluid, the subfoveal choroidal thickness gradually decreased throughout the 2-year follow-up period. Although reduction of choroidal thickness following PDT is a well-known finding in various retinal diseases, data on the long-term influence of PDT on choroidal structure are scarce.
Kucukevcilioglu and associates suggested that we compare the choroidal thickness in both eyes of patients with unilateral disease. Unfortunately, optical coherence tomography of the unaffected contralateral eye was available in only 10 eyes. The baseline subfoveal choroidal thickness was significantly greater in CSC eyes than in the contralateral eyes (CSC eyes, 404.9 ± 132.5 μm vs contralateral eyes, 345.8 ± 106.8 μm; P = .009, Wilcoxon signed-rank test). However, 2 years after PDT, the choroidal thickness of the CSC eyes decreased to the same level as that of the contralateral eyes, with no significant differences between the values of the affected and contralateral eyes (CSC eyes, 347.9 ± 127.1 μm vs contralateral eyes, 350.5 ± 108.7 μm; P = .878, Wilcoxon signed-rank test). Although only 10 cases were evaluated, this result suggests that PDT does not induce choroidal thinning in CSC eyes to a greater extent than that observed in eyes without disease activity after 2 years.
A recent study on subfoveal choroidal thickness following full-fluence or half-fluence PDT showed that the amount of choroidal thinning was significantly greater after full-fluence PDT than after half-fluence PDT, suggesting that PDT has a dose-dependent effect on choroidal thickness. In that study, the choroidal thickness in half-fluence PDT–treated eyes remained thicker than that in the contralateral eyes after 12 months. Further, the authors commented that choroidal thinning following PDT should be considered in the context of normalization of the pathologically increased choroid as opposed to the pathologic choroidal thinning that is observed in myopia or geographic atrophy. Another study on the long-term efficacy and safety of half-dose PDT showed that only 1 of 56 eyes (mean follow-up, 55.5 months) exhibited enlargement of retinal pigment epithelial atrophy. Furthermore, the shape of the autofluorescence changes did not correspond to the shape of the PDT spot, indicating that this might have been a result of the natural course of CSC rather than a direct PDT-related complication.
Therefore, there is presently no evidence that PDT induces significant choroidal thinning in CSC eyes compared to untreated eyes for as long as 2 years after treatment. In addition, it seems unlikely that PDT-induced choroidal thinning exceeds the normal range or that it significantly affects the health status of the choroid or retinal pigment epithelium in CSC patients. Based on these data, we believe that PDT should be actively considered for chronic CSC patients and that concerns about safety should not discourage treatment. However, further prospective studies with longer follow-up periods are needed to clarify these issues.