Optical coherence tomography angiography of non-exudative choroidal neovascularization
Age-related macular degeneration (AMD) has been classified in two groups, neovascular and non-neovascular, which historically has been synonymous with exudative and non-exudative, respectively. Neovascular AMD occurs when pathologic blood vessels, choroidal neovascularization (CNV), arise from the choroid and extend above Bruch’s membrane toward the outer retina. Often these vessels are exudative in nature, resulting in leakage of fluid, lipid exudate, or blood causing vision loss. The exudation from CNV allows detection as leakage with dye based angiography and as fluid with structural optical coherence tomography (OCT). In 2013, Querques et al. used multimodel imaging to detect treatment naïve quiescent CNV (1). This diagnosis requires presence of (I) moderate reflective material between an elevated retinal pigment epithelium and Bruch’s membrane on spectral domain OCT; (II) absence of fluid on OCT; (III) staining with fluorescein angiography; and (IV) a plaque identified with indocyanine green angiography. This study confirmed the existence of non-exudative neovascular AMD, and that exudation is not required for the presence of CNV. OCT angiography (OCTA), which can detect CNV as moving blood cells in the outer retinal slab (2) rather than relying on the presence of leakage on FA or fluid on OCT, is an ideal imaging modality to further study non-exudative CNV.