Prospective evaluation of changes in choroidal vascularity index after half-dose photodynamic therapy versus micropulse laser treatment in chronic central serous chorioretinopathy

Purpose To assess whether treatment of chronic central serous chorioretinopathy (cCSC) with photodynamic therapy (PDT) and high-density subthreshold micropulse laser (HSML) results in choroidal vascularity index (CVI) changes that may account for the treatment effect. Methods Patients with cCSC were prospectively included and analyzed. Patients received either half-dose PDT or HSML treatment. CVI of the affected and unaffected eye was obtained before treatment, 6 to 8 weeks after treatment, and 7 to 8 months after treatment. Results At baseline, 29 eyes (29 patients) were included both in the PDT and in the HSML group. The mean (± standard deviation) CVI change in the HSML group between before PDT and 6 to 8 weeks after PDT was − 0.009 ± 0.032 (p = 0.127), whereas this was 0.0025 ± 0.037 (p = 0.723) between the visit before PDT and final visit. The patients in the PDT group had a CVI change of − 0.0025 ± 0.037 (p = 0.723) between the visit before PDT and first visit after PDT, and a mean CVI change of − 0.013 ± 0.038 (p = 0.080) between the visit before PDT and final visit. There was no significant correlation between CVI and BCVA at the measured time points, in both the HSML group (p = 0.885), and in the PDT group (p = 0.904). Moreover, no significant changes in CVI occurred in the unaffected eye at any time point. Conclusions PDT and HSML do not significantly affect CVI, and therefore a CVI change may not be primarily responsible for the treatment effect. The positive treatment effect of both interventions may rely on other mechanisms, such as an effect on choriocapillaris and/or retinal pigment epithelium function.