EN FACE IMAGING

Three-dimensional angiographic imaging with the RTVue XR Avanti (Optovue) optical coherence tomography (OCT) system can provide a wealth of new information not obtained through fluorescein angiography in a wide range of retinal diseases, said Daniel Pauleikhoff MD, Saint Franziskus Hospital, Münster, Germany.

Dr Pauleikhoff stressed the revolutionary nature of the new technology, likening it to the advent of mobile phones and their subsequent rapid evolution into the smartphones of today.

“We should not imagine that we will continue to do the same thing for 20 or 30 years like fluorescein angiography, but rather that new technologies that are developing will give us totally different things and possibilities of which we at the moment are probably not aware,” he said.

He noted that the principle behind OCT angiography is that the horizontal volume scan and the vertical volume scan are both performed within a very short interval. The difference between the two scans, as measured with split-spectrum amplitude-decorrelation angiography (SSADA) software, enables the detection and quantification of blood flow in the vasculature being examined.

Furthermore, the technology enables the en face segmentation of the intraocular anatomy into different layers, allowing visualisation of the three-dimensional structure of the total retinal and choroidal vascularisation within seconds.

The Optovue Avanti is the first OCT device to provide OCT angiography, while others coming online include the angiography modules for the SPECTRALIS (Heidelberg Engineering) and the CIRRUS HD-OCT (ZEISS) devices.

BENEATH THE SURfACE

Dr Pauleikhoff noted that his initial experience with the Optovue device showed a good correlation with findings obtained through fluorescein angiography. The technology provides a clear differentiation between occult and classic choroidal neovascularisation (CNV). It also reveals previously hidden aspects of the disease.

For example, with OCT angiography it becomes clear that occult CNV lesions extend into the choroid and corneal capillaries, and the classic CNV lesions extend to the outer retinal pigment epithelium and the outer retina, he noted. OCT angiography also reveals changes deep in the retina, not visible with fluorescein angiography, in eyes with branch vein occlusion, diabetic macular oedema and macular telangiectasia type 2.

However, he noted that the more three-dimensional vascular changes, like the neovascular complex found in exudative age-related macular degeneration (AMD) will require a more sophisticated diagnostic analysis strategy, which has still to be developed. He proposed a grading system based on the amount of distinctness of the suspected neovascularisation from the surrounding vasculature.

Daniel Pauleikhoff: dapauleikhoff@muenster.de