ABCA4 and age-related macular degeneration: Thus, retinal structural changes that are used to differentiate adult-onset STGD1 from AMD for example (such as the appearance of macular or peripheral yellow-white flecks present in the transition between retinal pigment epithelium (RPE) and photoreceptor outer segments), may not be the earliest biomarker and is not present in all patients at the first visit [(3), see Supplementary Table S3].