OCT Angiography May Better Diagnose, Manage Retinal Disease

Marlene Busko

April 30, 2015

A new study shows how optical coherence tomography (OCT) angiography can be used to visualize common retinal diseases such as diabetic retinopathy, age-related macular degeneration, and choroideremia, which are major causes of blindness.

Researchers led by Yali Jia, PhD, from the Casey Eye Institute, Oregon Health & Science University, Portland, present six commonly seen case scenarios in an article published online April 20 in the Proceedings of the National Academy of Sciences.

OCT angiography is approved for clinical use in Europe and Asia but has not yet been approved by the US Food and Drug Administration. However, ophthalmologists in several US centers have been using this technology in research studies for about 5 years, senior author David Huang, MD, PhD, also from the Casey Eye Institute, told Medscape Medical News.

This technology enables ophthalmologists to better visualize blood flow in the retina and choroid capillary network and to detect the growth of abnormal blood vessels (neovascularization). "Once it's approved by the FDA, I think it's going to be used more than fluorescein angiography, because it's less invasive, and fast," Dr Huang said. Ophthalmologists would only need a new-generation OCT instrument plus a new software algorithm, he added.

"Drs Huang and Jia are pioneers in the field who have invented a software algorithm that elegantly allows some OCT hardware to perform OCT angiography," Amir H. Kashani, MD, PhD, from Keck Medicine of the University of Southern California-Pasadena and the University of Southern California Eye Institute, Los Angeles, told Medscape Medical News.

Researchers at the University of Southern California have developed a similar way to perform OCT angiography, which appears to be as effective, he noted. "It is not yet clear which method will be the best or most clinically meaningful, but it is fair to say that OCT angiography is a significant breakthrough technology that can change the practice of ophthalmology in the next 10 years, similar to how OCT revolutionized ophthalmology in the past decade," Dr Kashani said.

Noninvasive 3D Imaging of Eye Vasculature

OCT is very useful for evaluating fluid accumulation and guiding treatment in retinal diseases, and it has become "the most commonly used imaging modality in ophthalmology," Dr Jia and colleagues write. However, to detect capillary dropout or neovascularization in diabetic retinopathy or age-related macular degeneration, ophthalmologists still use fluorescein dye to visualize the retinal vasculature and then use indocyanine green dye to evaluate the choroidal vasculature. The dyes require intravenous administration, which is time consuming and may cause adverse effects such as nausea and vomiting. Moreover, the two-dimensional images from this type of angiography may be blurred at the edges because of dye leakage.

Dr Jia and colleagues used a custom-built OCT angiography system or a commercially available OCT angiography system (RTVue-XR, Optovue), along with a proprietary split-spectrum amplitude-decorrelation angiography algorithm to show how this technology could be used for noninvasive vascular imaging of blood flow in the eye in a clinical setting.

They report three major findings. First, OCT angiography with split-spectrum amplitude-decorrelation angiography captured a large, 6 × 6 mm view of the macula with adequate resolution, using a commercially available OCT system, Dr Jia and colleagues write.

Second, the colored display shows multiple vasculatures in the same image panel, so abnormalities can be located more precisely with minimal interference from artifacts.

Third, to the best of their knowledge, this is the first time that retinal neovascularization as well as the capillary dropout area in the retinal circulation and choriocapillaris were quantified in vivo.

"It is exciting that we can finally visualize the capillary level detail of the retina in real time," Dr Kashani said. Although ophthalmologists have known for decades that the earliest pathological signs of retinal vascular diseases such as diabetic retinopathy occur in the capillaries, until now the disease was only detected at more advanced stages, he noted.

However, "with OCT angiography, we now have a way to noninvasively, safely, and effectively visualize the earliest pathological changes in some of the most prevalent [diseases that cause blindness, which] will very likely lead to earlier diagnosis and more effective treatments."

The study was supported by grants from the National Institutes of Health, a Clinical and Translational Science Award, an unrestricted grant and Career Development Award from Research to Prevent Blindness, an Enhanced Career Development Award from the Foundation Fighting Blindness, and grants from the German Research Foundation. Dr Huang, Dr Jia, one coauthor, and the Oregon Health & Science University have a significant financial interest in Optovue. The researchers have submitted a patent application for the split-spectrum amplitude-decorrelation angiography algorithm and have licensed it to Optovue. Dr Huang and the coauthor receive royalties on an OCT patent licensed by MIT to Carl Zeiss Meditec. Two coauthors received royalties from intellectual property owned by MIT and licensed to Optovue. Dr Kashani reports that his employer, the University of Southern California, receives research support from Carl Zeiss Meditec for the study of OCT Angiography.

Proc Natl Acad Sci. Published online April 20, 2015. Abstract

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