Optical coherence tomography angiography in retinal diseases

Abstract

Optical coherence tomography angiography (OCTA) is a new, non-invasive imaging system that generates volumetric data of retinal and choroidal layers. It has the ability to show both structural and blood flow information. Split-spectrum amplitude-decorrelation angiography (SSADA) algorithm (a vital component of OCTA software) helps to decrease the signal to noise ratio of flow detection thus enhancing visualization of retinal vasculature using motion contrast. Published studies describe potential efficacy for OCTA in the evaluation of common ophthalmologic diseases such as diabetic retinopathy, age related macular degeneration (AMD), retinal vascular occlusions and sickle cell disease. OCTA provides a detailed view of the retinal vasculature, which allows accurate delineation of microvascular abnormalities in diabetic eyes and vascular occlusions. It helps quantify vascular compromise depending upon the severity of diabetic retinopathy. OCTA can also elucidate the presence of choroidal neovascularization (CNV) in wet AMD. In this paper, we review the knowledge, available in English language publications regarding OCTA, and compare it with the conventional angiographic standard, fluorescein angiography (FA). Finally, we summarize its potential applications to retinal vascular diseases. Its current limitations include a relatively small field of view, inability to show leakage, and tendency for image artifacts. Further larger studies will define OCTA's utility in clinical settings and establish if the technology may offer a non-invasive option of visualizing the retinal vasculature, enabling us to decrease morbidity through early detection and intervention in retinal diseases.

Optical Coherence Tomography Angiography Findings in Dengue-Related Maculopathy: A Case Report

“…It shows both structural and blood flow changes, and provides a highly detailed view of the retinal vasculature. 20 In our case, the OCTA showed an irregular enlargement of the foveal avascular zone, with loss of capillaries superiorly, in the internal and external retinal plexus.…”

Image artefacts in swept-source optical coherence tomography angiography

“…OCTA provides a three-dimensional vascular mapping at the microcirculation level and has shown its ability to identify important vascular changes in different retinal and choroidal diseases including diabetic retinopathy, retinal vascular occlusions and choroidal neovasculartisation (CNV) 1 2…”

Treatment of Macular Degeneration with Sildenafil: Results of a Two-Year Trial

“…Most recently, ultrafast ultrasound imaging has been demonstrated to provide depictions of choroidal flow dynamics, including velocities over the cardiac cycle [21]. These imaging techniques provide documented substantiation of increased choroidal perfusion [22]. Overall, these techniques show growing promise for even more precise measurements of choroidal perfusion in the future and should be developed further.…”

“…We have shown that sildenafil mediates choroidal flow by determining the fraction of the choroid occupied by measurable flow (decorrelation) using the swept-mode ultrasound imaging technique as a proxy for choroidal perfusion [21]. A similar processing scheme is currently used in split-spectrum OCT angiography to define the vascular density (the percentage area occupied by blood vessels) having at least two standard deviations above noise [22]. Most recently, ultrafast ultrasound imaging has been demonstrated to provide depictions of choroidal flow dynamics, including velocities over the cardiac cycle [21].…”