The initiating events are considered to be generated by known as well as unknown genetic and environmental factors that may affect the Bruch membrane/choroid (BM/C), RPE, or photoreceptor cells (PRCs). The metabolic interdependence of the tissues is such that changes in any one would inevitably influence the others, giving rise to a complex of intermediate disease mechanisms of which little is known. The final events of GA, CNV, and PED are partially understood. It is likely that effective therapeutic intervention at any stage of the disease evolution would be of benefit and that successful treatment directed at one tissue would have a beneficial effect on other tissues.