Supplementary Material for: The Progression of the Stargardt Disease Type 4 (ProgStar-4) Study: Design and Baseline Characteristics (ProgStar-4 Report No. 1)

<b><i>Background/Aims:</i></b> To describe the design and baseline characteristics of patients enrolled in the multicenter, prospective natural history study of Stargardt disease type 4. <b><i>Methods:</i></b> Fifteen eligible patients aged 6 years and older at baseline, harboring disease-causing variants in the <i>PROM1</i> gene, and with specified ocular lesions were enrolled. They were examined at baseline using a standard protocol, with 6 monthly follow-up visits for a 2-year period including best-corrected ETDRS visual acuity, spectral-domain optical coherence tomography, fundus autofluorescence (FAF), mesopic and scotopic microperimetry (MP). Areas of definitely decreased FAF (DDAF) and questionably decreased FAF were outlined and quantified on FAF images. <b><i>Results:</i></b> Amongst the 15 patients (29 eyes) that were enrolled at 5 centers in the USA and Europe, 10 eyes (34.5%) had areas of DDAF with an average lesion area of 3.2 ± 3.5 mm² (range 0.36–10.39 mm²) at baseline. The mean retinal sensitivity of the posterior pole derived from mesopic MP was 8.8 ± 5.8 dB. <b><i>Conclusions:</i></b> Data on disease progression in <i>PROM1</i>-related retinopathy from this study will contribute to the characterization of the natural history of disease and the exploration of the utility of several modalities to track progression and therefore to potentially be used in future interventional clinical trials.