Inclusion criteria in AREDS2 resulted in the enrollment of participants with intermediate AMD, defined by the presence of large drusen, with and without additional pigmentary changes. Owing to the longitudinal nature of AREDS2 study, anatomical features of AMD in study participants can be monitored and characterized as a function of time to further understand the steps in AMD progression. Spectral domain OCT (SDOCT) is a non-invasive imaging technology that has the speed and resolution to image fine structures such as drusen and the photoreceptor layers. With annotation and processing of three-dimensional SDOCT scans, focal AMD pathology such as drusen can be mapped and monitored over time. The AREDS2 Ancillary SDOCT Study (A2A SDOCT) added the use of novel higher resolution three-dimensional OCT retinal imaging at four AREDS2 study centers to examine 400 of the participants in the AREDS2 clinical trial.