Optical Coherence Tomography-Angiography in Geographic Atrophy

Geographic atrophy (GA) represents the non-exudative late stage of age-related macular degeneration and constitutes a leading cause of legal blindness in the developed world. It is characterized by areas of loss of outer retinal layers including photoreceptors, degeneration of the retinal pigment epithelium, and rarefication of the choriocapillaris. As all three layers are functionally connected, the precise temporal sequence and relative contribution of these layers towards the development and progression of GA is unclear. The advent of optical coherence tomography angiography (OCT-A) has allowed for three-dimensional visualization of retinal blood flow. Using OCT-A, recent studies have demonstrated that choriocapillaris flow alterations are particularly associated with the development of GA, exceed atrophy boundaries spatially, and are a prognostic factor for future GA progression. Furthermore, OCT-A may be helpful to differentiate GA from mimicking diseases. Evidence for a potential protective effect of specific forms of choroidal neovascularization in the context of GA has been reported. This article aims to give a comprehensive review of the current literature concerning the application of OCT-A in GA, and summarizes the opportunities and limitations with regard to pathophysiologic considerations, differential diagnosis, study design, and patient assessment.