Optical Coherence Tomography Angiography in Healthy Subjects and Diabetic Patients

Fluorescein angiography and indocyanine green angiography provide information about the normal retinal and choroidal vascular perfusion. They allow the evaluation of different diseases and increase the capability to define and diagnose several pathological conditions. Fluorescein angio graphy is the "gold standard" in imaging the retinal vascular bed and its changes, although not all the different layers of the capillary network can be visualized in a bidimensional examination. Optical coherence tomography angiography allows a depth-resolved visualization of the retinal and choroidal microvasculature, by calculating the difference (decorrelation) between static and nonstatic tissue. Given that the main moving elements in the eye fundus are contained in vessels, determining a vascular decorrelation signal permits a three-dimensional visualization of the retinal and choroidal vascular network without the administration of an intravenous dye. Moreover, a complete morphofunctional assessment may help in defining both the origin and the clinical activity of different vascular diseases such as diabetic retinopathy.