OCT Angiography Predicts Exudation in Macular Degeneration

Laird Harrison

July 24, 2018

VANCOUVER, Canada — Optical coherence tomography (OCT) angiography can help predict which eyes affected by age-related macular degeneration are most likely to develop exudation, research shows.

The new technology can monitor choroidal neovascularization and potentially identify eyes that would benefit from prophylaxis, said investigator David Huang, MD, PhD, from Oregon Health and Science University in Portland.

"I believe the detection and monitoring of nonexudative CNV will become a killer app for OCT angiography," he told Medscape Medical News.

Huang presented data on a series of eyes with intermediate age-related macular degeneration here at the American Society of Retina Specialists 2018 Annual Meeting.

Current guidelines recommend that eyes with neovascular age-related macular degeneration be treated only when they become exudative. But by then, some visual acuity can already have been lost. Treating the eyes earlier might prevent this damage.

Conventional imaging techniques cannot predict which eyes are most likely to become exudative, Huang explained. "You cannot detect nonexudative CNV with clinical fundus examination, fluorescein angiography, or structural OCT. OCT angiography is needed."

OCT angiography scanners can create about 70,000 images of the back of the eye in 3 seconds and at the same time correct for blinking and microsaccades. The technology can show the flow of blood and produce detailed images of blood vessels in the retina.

Researchers are just beginning to figure out the best uses for the new technology.

You cannot detect nonexudative CNV with clinical fundus examination, fluorescein angiography, or structural OCT. OCT angiography is needed.

To see whether the choroidal neovascularization frequently detected by OCT angiography correlates with exudation, Huang and his colleagues followed 63 patients who had intermediate nonexudative age-related macular degeneration in one eye and exudative disease in the other.

Every 6 months, the nonexudative eyes were scanned with 6 × 6 mm and 3 × 3 mm OCT angiography (AngioVue, Optovue).

During a follow-up period of at least 24 months, ten eyes developed nonexudative choroidal neovascularization.

In the eight eyes that leaked within 10 months, progression of choroidal neovascularization was rapid. In the two eyes that did not leak, progression was slow. In all the eyes, treatment with a vascular endothelial growth factor (VEGF) inhibitor stopped this progression.

Of the 53 eyes that did not develop choroidal neovascularization, few progressed to exudation.

In fact, eyes were 18.1 times more likely to progress to exudation if choroidal neovascularization was identified on OCT angiography than if it was not.

The study shows the value of OCT angiography for eyes with nonexudative neovascular by age-related macular degeneration, Huang said.

He recommends close monitoring of such eyes with OCT angiography for the first month to watch for rapid progression. "The rate of growth of nonexudative CNV can be measured by OCT angiography, and might serve as the key metric to guide treatment," he explained.

Without a clinical trial or new guidelines, though, "exudation is still the primary factor in deciding whether you need to treat," Huang said. "A clinical trial is needed to show whether these nonexudative lesions need to be treated."

Still, this study suggests the feasibility of a future protocol in which OCT angiography is used to guide prophylaxis in fellow eyes, said session moderator Manish Nagpal, MBBS, DO, from the Retina Foundation in Ahmedabad, India.

"If the correlation is good, it could be a very good technique," he told Medscape Medical News. "Once exudation starts, even when you treat, you do lose some vision." That vision can sometimes be restored, but prophylactic treatment might be a better option because it could prevent the retina from ever lifting, he said.

Age-related macular degeneration is not the only condition in which OCT angiography might prove useful.

Less-Invasive Option for Diabetic Retinopathy

A separate study of ultra-widefield OCT angiography to monitor patients with diabetic retinopathy was presented by Kasra Rezaei, MD, from Associated Retina Consultants in Phoenix.

Because the detailed visualization of vascular networks covers a field of view of about 120 degrees, the technology can be used to locate the area of neovascularization in the peripheral retina and the capillary impairment zone, and to measure retina vascular density and vessel diameter, Rezaei explained.

In this way, OCT angiography can help monitor the progression of diabetic retinopathy and responses to treatment, he added.

However, unlike in eyes with age-related macular degeneration, the information provided by OCT angiography in eyes with diabetic retinopathy can also be obtained with fluorescein angiography, Nagpal said.

The main advantage of OCT angiography is that it is less invasive because no contrast agent is required, he explained. So this technology would be a good option for patients with a contraindication for fluorescein.

The macular degeneration study was supported by the National Institutes of Health, Research to Prevent Blindness, Champalimaud Foundation and Optovue. Huang reports a financial relationship with Optovue. Nagpal reports a financial relationship with Nidek.

American Society of Retina Specialists (ASRS) 2018 Annual Meeting. Presented July 23, 2018.

Follow Medscape on Twitter @Medscape and Laird Harrison @LairdH

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