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Optical Coherence Tomography Angiography Revolutionizes Ocular Flow Assessment

Dual-modality system allows for 3D viewing without staining.

BY KAREN APPOLD, CONTRIBUTING WRITER

Optovue’s (Fremont, CA) AngioVue imaging system combines OCT with angiography (OCTA) for the first time, enabling the assessment of microvasculature and perfusion with unprecedented detail. No contrast medium is needed, permitting noninvasive procedures, and AngioVue data are three-dimensional and depth-resolved. Before now, OCTA was only available in research prototypes.

Caroline R. Baumal, MD, of New England Eye Center in Boston was prompted to try AngioVue because “imaging retinal and choroidal vasculature without dye injection would greatly benefit patients.” Multiple factors can preclude the use of intravenous fluorescein angiography, such as allergy. Eliminating the risk of an adverse reaction is an advantage of OCTA, as this can potentially be a serious issue. Because the majority of her patients have wet AMD and diabetic retinopathy, they are ideal candidates for this type of imaging.

QUICK AND IN-DEPTH, TOO

Another advantage, Dr. Baumal reports, is AngioVue’s fast imaging time of three seconds per scan, which enables retinal physicians to image patients faster and potentially perform OCTA more frequently than with FA or ICG angiography. In comparison, dye-based angiography can take up to 30 minutes.

Images can be segmented into layers of retinal and choroidal anatomy to allow for visualization of the microvasculature within specific layers of the retina, without the blurring or obscuring effects of fluorescein staining or pooling. Deep choroidal imaging is also possible, as AngioVue can visualize small capillaries such as deep retinal capillary plexus and radial peripapillary capillaries. “Clinicians can see much finer detail compared to FA of the vascular plexuses,” says Jay Wei, founder and CEO, Optovue. “This enables them to look for very small changes that may ultimately lead to vision loss.”

Dr. Baumal finds the layout of the standardized OCTA scans user friendly. The machine offers a variety of printouts, including segmented OCTA with corresponding high-definition B-scans. “This is an improvement over present technology,” she says, noting that the images are high resolution with a range of 5 µm transverse resolution.

AngioVue uses motion contrast to distinguish the presence or absence of ocular blood flow. Sequential OCT B-scans are acquired at a single cross-section of the retina and are compared. Differences between scans indicate motion or flow. “The ability to scan through the 3D image is really innovative,” Dr. Baumal says. “The OCTA image combined with the OCT B-scan gives combined static flow and structural information.”

VERSATILE CLINICAL UTILITY

Retinal physicians are currently exploring the range of clinical applications for OCTA. Early work shows that the technology is beneficial in evaluating patients who are at risk of, or are being treated for, neovascular AMD, choroidal neovascularization, and retinovascular abnormalities such as diabetic retinopathy, and retinal vein and artery occlusion. “This is because AngioVue can quantify the flow density, flow area, and nonflow area,” Wei says. “It can be used to track change over time with quantification measurements.”

These disorders are a major cause of retinal morbidity, Dr. Baumal notes. OCTA imaging features have also been described in other disorders, including macular telangiectasia and CSC.

Although not currently available in the US, physicians who use Optovue’s Avanti Widefield OCT may upgrade to the AngioVue when it receives regulatory clearance in their countries. RP