Optical Coherence Tomography Angiography in Diabetic Maculopathy.

Abstract

Fluorescein angiography (FA) and indocyanine green angiography have provided information about the normal retinal and choroidal anatomy, nearly comparable to histological findings. These tests have been fundamental in the evaluation of all retinal and choroidal vascular diseases and have allowed clinicians to define and diagnose several pathological conditions. FA became the "gold standard" in retinal imaging due to the capacity to visualize the retinal capillary bed and its changes, both in the macular area and in the periphery. Although the fluorescence of the injected dye enabled improved visualization of retinal capillaries, not all the different layers of the retinal capillary network could be visualized in this bi-dimensional examination, mainly because of the light scattering phenomenon. By calculating the difference between static and non-static tissues, optical coherence tomography angiography (OCT-A) allows a depth-resolved visualization of the retinal and choroidal microvasculature. Given that the main moving elements in the ocular fundus are contained in blood vessels, determining a vascular decorrelation signal enables visualization of the 3-dimensional retinal and choroidal vascular networks without the intravenous dye injection, reducing therefore the risk of potential adverse events. Since OCT-A is perfectly co-registered with its structural OCT, both morphological findings, such as macular edema, and functional ones, like capillary drop-out, may be clearly evaluated on a single dye-free examination. Proficient detection of the different findings in diabetic maculopathy on OCT-A can result in a rapid analysis of the examination, and in the capacity to distinguish truly decorrelated structures (perfused vessels) from artifacts. Moreover, a complete morpho-functional assessment may help in determining both the origin and the clinical activity of a given vascular disease.