NEW PRODUCT APPLICATIONS

Getting a Detailed Look at Retinal Disease

Imaging system employs optical coherence tomography angiography to obtain in-depth segmented microvascular images

BY KAREN APPOLD, CONTRIBUTING WRITER

David Sarraf, MD, clinical professor of ophthalmology, Retinal Disorders and Ophthalmic Genetics Division, Stein Eye Institute, University of California, Los Angeles, was eager to employ Optovue’s AngioVue Imaging System using optical coherence tomography angiography (OCTA) knowing that he could better visualize the deep retinal capillary system in isolation and detect microvascular morphology of neovascular lesions without dye injection.

“En face segmentation allows physicians to independently analyze the superficial and deep retinal capillary plexus (DCP) as well as the choriocapillaris,” Dr. Sarraf says. Segmentation of the retina, layer by layer, allows physicians to study the retinal and choroidal microvasculature — which is not easily identified with fluorescein (the current angiography imaging standard) and indocyanine green (ICG) angiography.

OCTA uses a standard OCT platform, but can integrate the properties of either phase or amplitude decorrelation to detect motion and blood flow. “Vessels can be visualized if the flow exceeds the system’s detection threshold,” Dr. Sarraf explains.

CLINICAL APPLICATIONS

Physicians can use AngioVue OCTA to image blood vessel abnormalities characteristic of diabetic retinopathy and wet age-related macular degeneration (AMD). The hallmark finding of wet AMD includes neovascularization that can originate from the retina or choroid below the retinal pigment epithelium. “Our system is ideally suited for imaging this abnormality as it progresses in size and morphology,” says Tony Ko, PhD, vice president of research and development, Optovue, Fremont, CA. “By having the ability to image changes in a neovascular lesion, clinicians can better prescribe treatments and manage patients. In diabetic retinopathy, the foveal avascular zone is the area of interest as it increases and becomes more irregular in shape. As the disease progresses, the density of blood vessels decrease.”

In addition, evaluating the DCP is an important advantage of OCTA systems for patients who have retinal vascular disease such as diabetic retinopathy or sickle cell retinopathy. “The DCP is poorly visualized by conventional dye-based angiography methods, and there is growing evidence that the DCP may be preferentially affected in retinal vascular diseases such as diabetic retinopathy, sickle cell retinopathy, and retinal vascular occlusive disorders,” Dr. Sarraf says.

Type 1 neovascular lesions that are occult, latent, and reside under a pigment epithelial detachment (as in common disorders such as AMD and chronic central serous retinopathy) can be challenging to identify, Dr. Sarraf adds. OCTA has become an integral tool to help detect these lesions in order to better guide prognosis, follow-up, and therapy.

BENEFITS TO PATIENTS

The noninvasive nature of AngioVue’s image acquisition greatly reduces testing time. Technicians can acquire each scan in less than three seconds, while fluorescein and ICG angiography may require 10 to 30 minutes of patient testing time.

Another advantage of being noninvasive is that images can be acquired as often as necessary to assess disease progression and treatment response, Dr. Ko says, which allows clinicians to follow patients more closely and adjust their treatment plans accordingly.

In addition, the use of dye contrast requires an intravenous injection and can have systemic complications. “OCTA doesn’t expose patients to the possible systemic adverse effects of a contrast dye,” Dr. Ko says.

EASE OF USE

OCT angiography currently employs scanning speeds of 70,000 to 100,000 A-scans per second. Technicians do not need a high level of skill or experience to use Optovue’s instrument. Physicians can easily view images in an exam room or on an office computer.

While OCTA technology is still evolving and requires technical improvements in order to seamlessly integrate this system into a busy clinical retinal practice, the information that these systems have provided has already remarkably improved physicians’ understanding and management of retinal disease, Dr. Sarraf concludes. RP