Reduced-fluence photodynamic therapy versus placebo for central serous chorioretinopathy (REPLAY trial): rationale and study protocol of a pivotal double-blind randomised controlled trial.

introductionChronic central serous chorioretinopathy (CSC) can cause progressive and permanent vision loss. Although photodynamic therapy (PDT) is a primary treatment option globally, it is not approved for CSC worldwide, limiting therapeutic access. The REPLAY trial is a phase III, investigator-initiated trial to evaluate the efficacy and safety of reduced-fluence PDT (rf-PDT) for chronic CSC to seek the first regulatory approval globally. METHODS AND ANALYSIS: This study comprises two cohorts. The 'untreated cohort' is a multicentre, randomised, placebo-controlled, double-masked trial involving 60 patients with untreated, fovea-involving chronic CSC, randomised 2:1 to receive a single rf-PDT or placebo treatment. The 'previously treated cohort' is a single-arm, open-label trial for up to 10 patients with recurrent CSC after PDT. The primary endpoint for both cohorts is the proportion of eyes with a complete resolution of subfoveal fluid at 12 weeks post-treatment, assessed by optical coherence tomography. Secondary endpoints include changes in best-corrected visual acuity, central choroidal thickness, recurrence rates and incidence of adverse events over a 48 week follow-up. ETHICS AND DISSEMINATION: The study protocol was approved by the Kyoto University Hospital Institutional Review Board, IRB of Chiba University Hospital, Tokyo Women's Medical University Institutional Review Board and Institutional Review Board of Kansai Medical University Hospital. Written informed consent is obtained from all participants. The results will be disseminated through publication in a peer-reviewed journal and presentations at scientific conferences. TRIAL REGISTRATION NUMBER: jRCT2051230156 (URL: https://jrct.mhlw.go.jp/latest-detail/jRCT2051230156).