Optical Coherence Tomography Angiography in Healthy Subjects and Diabetic Patients

Abstract

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.

Retinal Nonperfusion Relationship to Arteries or Veins Observed on Widefield Optical Coherence Tomography Angiography in Diabetic Retinopathy

“…13,20,21 The results herein agree with these findings (Table). Furthermore, compared to FA, OCTA can also visualize periarterial capillary-free zones [16][17][18] and vessel connections at the level of precapillary arterioles and venules. These advantages enabled us to identify and trace small branches of arteries and veins on OCTA images.…”

“…As mentioned previously, OCTA visualizes a narrow capillary-free zone that physiologically exists around retinal arteries. [16][17][18] Automated quantification could erroneously detect this physiologic zone as a nonperfusion area, and the A/V ratio could have been overestimated because the periarterial physiologic capillary-free zones could still contribute to nonperfusion areas when combined with actual areas of nonperfusion in eyes with DR. However, we confirmed manually that this physiologic capillary-free zone was not detected as areas of nonperfusion by our software in eyes without DR. 13 Moreover, a very recent study quantitatively demonstrated that the periarterial capillary-free zone in severe NPDR was enlarged compared to that in the normal subjects.…”

“…OCTA images allowed the visualization of arterial branches, which are clearly distinguishable from veins by the presence of surrounding hypointense areas, representing the capillary-free zone, due to the absence of efferent vessels coming directly out of walls. [16][17][18] Furthermore, arteries do not cross other arteries, and veins do not cross other veins. Based on these characteristics, arteries and veins were manually traced up to the level of precapillary arterioles and venules.…”

Choroidal vascularity index as a biomarker of systemic inflammation in childhood Polyarteritis Nodosa and adenosine deaminase-2 deficiency

“…The choriocapillaris becomes wider and longer towards the equatorial region. In contrast to other capillary networks throughout the human body, the luminal diameter of these capillaries is significantly larger (approximately 20 μm at the macula and 18-50 μm at the periphery) [14]. Macula involves high density of photoreceptors, that results in a high metabolic demand at this region which is supplied primarily by choroid.…”

Discordant vascular parameter measurements in diabetic and non-diabetic eyes detected by different optical coherence tomography angiography devices

“…Recent literature has highlighted the importance of changes in choroidal blood flow in patients with diabetic retinopathy. [6][7][8] Therefore, a comprehensive evaluation of OCTA imaging in DR should consider the choroid in addition to the retina.…”