System offers advanced capabilities in OCT, OCTA

Reviewed by Philip J. Rosenfeld, MD, PhD

The recent FDA clearance of a swept-source optical coherence tomography (OCT) and OCT angiography (OCTA) platform (PLEX Elite 9000, Carl Zeiss Meditec) for posterior ocular structures enables fast, dense, wide, and deep imaging of the retina, choroid, and their associated microvasculature, said Philip J. Rosenfeld, MD, PhD.

This high-end technology is expected to be a valuable tool for retinal disease research, as well as patient care, he noted.

Dr. Rosenfeld, professor of ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, is the chairman of a global consortium of clinician scientists set up by Carl Zeiss Meditec to conduct cutting-edge retinal disease research using the new system. Purchasers are required to join the collaborative research effort-known as the Advanced Retina Imaging (ARI) Network-to exchange ideas and findings and work with scientists and developers on technological innovations and clinical applications of OCT technology.

Several prospective studies will be under way soon, according to Dr. Rosenfeld.

Greater detail

Greater detail

The wide-field, high-resolution visualization of the platform will enhance the ARI’s investigations, Dr. Rosenfeld noted.

“It’s a marvelous piece of technology, and we can see things that we have never seen before,” he said. “With this system, we can obtain both a standard OCT image and an image showing blood flow, both generated from the same dataset. By scanning at a rate of 100,000 A-scans per second, we can rapidly obtain images that are visualized in real time for patient care or stored for research purposes.

“While it’s primarily a research tool right now, my prediction is that it’s going to become the standard-of-care instrument within the next few years,” Dr. Rosenfeld said.

To help offset qualms from physicians who are hesitant to invest in the new system despite its advanced capabilities, the manufacturer will include free software and hardware upgrades for the next several years, including an upgrade this year expected to double the speed of the laser to 200,000 A-scans per second with even faster scanning rates in the years ahead.

The technical specification of the system include a swept-source tunable laser centered at 1050 nm and a scan speed of 100,000 A-scans at a tissue depth of 3 mm. The axial resolution is 6.3 µm and offers fields of view ranging from 3 × 3 mm up to 12 × 12 mm. Wider field images are planned later this year.

Making the case for an investment in swept-source OCT and OCT angiography, whether now or later, Dr. Rosenfeld describes it as a replacement for today’s standard-of-care retinal imaging protocols.

“The future includes both structural imaging and OCT angiographic imaging through an undilated pupil and increased efficiency of patient care,” Dr. Rosenfeld said.

“The need for fundus photography, fluorescein or indocyanine green angiography, or even a dilated fundus exam, will greatly decrease,” he said. “Imaging will be faster and patients will prefer it to being dilated and having a bright flash of light in their eyes. It can also be frequently repeated, and I predict the information will significantly enhance patient management and outcomes. All we need for most patients with macular disease is a 7- to 8-second scan with this OCT, and we get all of the information we need.”

Though the image quality with spectral-domain OCT is similar to that of swept-source OCT angiography for macular diseases that affect the retina above the retinal pigment epithelium (RPE), swept-source OCT is faster and therefore can generate wider-field images, according to Dr. Rosenfeld.

Monitoring patients

Monitoring patients

When monitoring diabetic patients with macular neovascularization or individuals with macular edema, a single 12- × 12-mm swept-source image will provide a sufficiently detailed, comprehensive view of the affected area. Swept-source OCT is also useful for screening patients with diabetes whose eyes show early signs of change but have not yet developed visual complications, and more importantly, can visualize neovascularization before it could be detected with a fundus exam.

“That changes how you manage the patient and how you follow the patient,” Dr. Rosenfeld said.

For managing diseases below the RPE, such as age-related macular degeneration or polypoidal choroidal vasculopathy, the longer wavelength of swept-source OCT is a significant advantage. Spectral-domain OCT has a wavelength of 840 nm, whereas that of swept-source is 1,050 nm, and this longer wavelength penetrates the RPE much better with less sensitivity roll-off into the choroid.

Dr. Rosenfeld and colleagues are conducting a prospective study in patients with dry AMD and have found that with the platform they can see blood vessels growing months before leakage occurs.

“It has revolutionized the way we think about dry and wet AMD,” he said. “We now can identify the patients with neovascularization months before they develop exudation and vision loss. 

“We’re following these patients without treatment, trying to identify the changes in neovascularization that precede the exudation,” Dr. Rosenfeld added. “We’re catching patients at an earlier stage of exudation with better vision, and hopefully this will translate into better long-term vision.”

As part of the study, the investigators also monitor the effects of treatment in patients who have developed exudation. The new imaging technology enables them to visualize the status of the blood vessels and helps them determine when to re-treat and the appropriate treatment intervals. 

Philip J. Rosenfeld, MD, PhD

E: prosenfeld@med.miami.edu

Dr. Rosenfeld receives research support from Carl Zeiss Meditec and is a consultant to the company.