OCTA providing two-for-one imaging and practical value

OCT angiography (OCTA) is a revolutionary new tool that adds value to clinical practice. It provides unique insights about retinal and choroidal vasculature compared with conventional OCT along with the advantages of conventional dye-based techniques, said Philip J. Rosenfeld, MD, PhD, at the 2017 Retina Subspecialty Day meeting.

“With a single volume scan, OCTA provides both structural imaging and vascular flow imaging, and therefore it offers multimodal imaging with a single modality,” said Dr. Rosenfeld, professor of ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami.

“In addition, OCTA imaging is rapid, noninvasive, can be done without pupil dilation, and does not involve bright flashes of light or venipuncture,” he said. “Therefore, it is safer than fluorescein angiography and indocyanine green (ICG) angiography and much preferred by patients. For these reasons, and because OCTA is less expensive and safer than dye-based imaging, it is also much better suited for serial follow-up.”

OCTA is available on spectral-domain and swept-source (SS) OCT platforms. Dr. Rosenfeld said he has been studying the two systems in parallel and prefers the SS technology because it provides better imaging under the retinal pigment epithelium (RPE).

“Thus, SS-OCTA is the better strategy for visualizing type 1 neovascularization in eyes with age-related macular degeneration (AMD), polypoidal choroidal vasculopathy, the choriocapillaris, and any macular diseases that involve the choroid and is complicated by choroidal neovascularization,” he said.

Among its clinical applications, Dr. Rosenfeld said he considers the ability of OCTA to identify eyes with “nonexudative neovascular AMD” as its greatest utility. These eyes are defined by the presence of nonexudative AMD with subclinical neovascularization.

Previous studies in the 1990s used ICGA to identify these subclinical lesions, and while they retain good vision, they were at increased risk for developing active exudation when compared with eyes without these subclinical lesions.

“We confirmed this risk in a recent study including 160 eyes,” Dr. Rosenfeld said.

“Although anti-VEGF treatment for these subclinical neovascularization is not recommended, by detecting the neovascularization, OCTA identifies patients who should have close clinical follow-up and daily home monitoring to allow early detection of exudation,” he said. “To me, that makes OCTA a real breakthrough in patient care.”

He added that while the subclinical neovascular lesions could also be detected with ICGA, ICGA would not be considered for use as a screening tool because of its invasive nature.

“OCTA is easier and safer,” Dr. Rosenfeld said.

Other applications

Because of its ability to identify or exclude neovascularization when macular fluid is present, OCTA has value for diagnosing conditions that may masquerade as macular neovascularization, including large non-vascularized serous pigment epithelial detachments, drusen with associated subretinal fluid, chronic central serous chorioretinopathy, and vitelliform maculopathies, among others.

By identifying or excluding neovascularization in these cases and also in eyes with inflammation, the findings from OCTA can guide appropriate treatment.

“For example, in a patient with drusen and associated fluid, sometimes the fluid arises in the absence of neovascularization and can resolve spontaneously,” Dr. Rosenfeld said. “OCTA helps us identify when anti-VEGF therapy is needed or when such an eye can just be observed.

“With inflammatory diseases, the decision of whether to treat with a corticosteroid or anti-VEGF therapy will depend on whether or not neovascularization is present,” Dr. Rosenfeld said.

As another application, OCTA has utility for defining the extent of disease in eyes with diabetic macular edema or retinal vein occlusion.

However, it has a limited role, if any, in the management of exudative AMD, Dr. Rosenfeld said.

“Being a strong advocate for OCTA, I have tried hard to find cases of exudative AMD where OCTA has added value by improving visual acuity outcomes, but conventional OCT already does an excellent job for management of patients being treated with anti-VEGF therapy,” Dr. Rosenfeld said. “Considering that we hardly use any dye-based angiography for managing patients with wet AMD, it stands to reason that there is really a limited role for OCTA as well.

“The major value of OCTA in exudative AMD is to confirm the presence of neovascularization after exudation is initially diagnosed with OCT,” he said.

Dr. Rosenfeld receives research funding and consulting fees from Carl Zeiss Meditec.