Non neovascular Age – related macular degeneration – Review on clinical and imaging advances

The aim of this review was to provide an overview of the principal features of non-neovascular age – related macular degeneration (NNAMD) and how they appear by multimodal imaging. None are specific of the disease, but their simultaneous detection, their distribution and the development in a particular age range allow to make the correct diagnosis. The current availability of different imaging modalities offers the chance to better characterize the disease and to detect the earliest changes, monitoring its progression to the late stage, known as geographic atrophy (GA). A recent consensus has provided a novel definition of GA, based on optical coherence tomography (OCT), introducing two novel concepts: incomplete and complete retinal pigment epithelium (RPE) and outer retinal atrophy (iRORA and cRORA, respectively). The main recognized risk factors for progression are soft drusen, drusenoid pigment epithelium detachment (PED), subretinal drusenoid deposits (SDD), intraretinal hyperreflective foci (iHRF) and acquired vitelliform lesion. Soft drusen represent one of the earliest signs of NNAMD and their confluence can lead to the development of drusenoid PED, whose height mainly correlates with progression. SDD have been better characterized after the advent of the OCT and differently from the drusen, the material accumulates above the RPE. iHRF could be observed in different retinal layers, but the involvement of the outer nuclear layer has been recognized to correlate more with GA development. The identification of valid biomarkers is crucial to monitor and predict the disease progression and to evaluate the efficacy of novel proposed therapies in clinical trials.