This article is more than 5 years old. Information may no longer be current.
Spectral-domain OCT offers potential in treating AMD
KOLOA, Hawaii — The advent of spectral-domain optical coherence tomography could signify a better standard of care for patients with age-related macular degeneration and other retinal diseases.
This is the opinion of Philip J. Rosenfeld, MD, PhD, who spoke on the newest generation of optical coherence tomography (OCT) during Retina 2007, held in conjunction with Hawaiian Eye 2007. Dr. Rosenfeld said the newest generation offers better image quality, segmentation of the macula, fundus reconstruction, image registration and other features that will enable specialists to become more familiar with the disease and its clinical manifestations. “We’re going to develop a greater anatomic appreciation of the diseased macula and how patients respond to therapy using this technology,” he said.
Features
Spectral-domain OCT offers advantages over traditional OCT in many aspects, especially imaging, Dr. Rosenfeld said.
“Rather than a single detector, as in the Stratus OCT [Carl Zeiss Meditec, Dublin, Calif.], there’s now a spectrometer that collects all the information at once and, based on Fourier transformation of these reflected frequencies, it can provide a beautiful map,” he said. “The spectral-domain OCT gives a much better anatomic representation of what the macula looks like, with higher resolution and fewer movement artifacts.”
Dr. Rosenfeld said the six diagonal scans are replaced with a rapid raster scanning technique without a moving reference arm to assess depth, so the scans are much faster, taking 2 seconds or less. Faster scans mean fewer movement artifacts and greater reproducibility. In addition, he showed that the new technology is compact enough to fit on a small platform.
Another asset of spectral-domain OCT, he said, is that you can combine all scans to reconstruct a virtual image of the fundus.
“You know exactly where you’re cutting. It’s remarkable that you can register exactly where the cuts are on the fundus image,” he said.
He added that spectral-domain OCT also provides a clear resolution of pathology on the retina, such as epiretinal membrane, as well as under the retina, as shown by the ability to view drusen topographically at the level of retinal pigment epithelium (RPE).
These images can then be segmented at various depths in the retina or under the retina to further examine the effects of the disease and its response to treatment.
“You can segment at any level,” Dr. Rosenfeld said. “Any layer you can detect using the OCT, you can also perform segmentation.”
Overall, preoperative spectral-domain OCT enables clinicians to view the fundus image, superimpose images, return to the exact slice and know exactly where they are cutting, he said.
After the surgery, he said, “You can look at your cases postop and it will be in the exact same place, and you can appreciate the outcomes of your surgery.”
Dr. Rosenfeld said all of the commercially available spectral-domain OCT devices should be able to provide similar tomographic images, because the hardware is very similar; however, the differences in the devices will reside in the software and the data manipulations.
At last year’s American Academy of Ophthalmology meeting, Reichert Ophthalmic Instruments, Ophthalmic Technologies and Heidelberg Engineering were among the companies displaying spectral-domain OCT systems.
Bioptigen announced U.S. Food and Drug Administration premarket approval of its spectral domain OCT system in January, and Carl Zeiss Meditec received its FDA approval in February. The Reichert SOCT Copernicus is pending 510(k) approval.
“This is all basically the same technology; it’s how the information is processed that is going to distinguish various companies,” Dr. Rosenfeld said.
Uses
Dr. Rosenfeld said he has enjoyed putting the features of spectral-domain OCT to use in everyday practice.
“One of the reasons that I am excited is it gives you ability to look at dry AMD in ways we never could before,” Dr. Rosenfeld said. “While histopathologic analysis of eyes with AMD showed us that the retina is thinned overlying drusen, the three-dimensional maps using spectral-domain OCT show us a lunar landscape with the retinal contour appearing as craters due to retinal thinning overlying the drusen.”
In addition, he said, spectral- domain OCT will be useful in mapping geographical atrophy by creating a virtual reconstruction of the fundus by showing increased reflection corresponding to geographic atrophy.
“When you look at the map, you can actually see, in the segmentation of the RPE, the depression that occurs with the geographic atrophy,” he said. “It also gives us a greater appreciation for epithelial detachment in [AMD].
“I’m looking forward to doing some longitudinal studies using this technology,” Dr. Rosenfeld said, pointing out that the point-to-point registration will allow a surgeon or research team to return to the exact same points over time and after treatment to evaluate change.
“It will provide better image quality and allow you to get these virtual images that you can put on top of the fundus image and get point-to-point registration,” he said. “You’re going to have more reliable algorithms when you get the 3-D reconstruction and get thickness measurements, but I think the value is that we’re going to gain a better understanding of the disease, so we can take better care of our patients.”
Cautious optimism
In a separate presentation, Jay S. Duker, MD, discussed another advancement to OCT technology, ultra-high resolution OCT. Although this is not commercially available because of the high cost of building it, he said, for research purposes, the advancements in imaging represent a “promising research tool.”
He also said he is “a little less optimistic than [Dr. Rosenfeld]” that spectral-domain OCT and ultra-high resolution OCT will be a “revolution in our field.”
“There is no evidence yet that it is improving our ability to treat disease, although it is helping us qualitatively visualize retinal pathology better,” he said.
Although the 3-D images are dramatic, he said he is not sure how clinically relevant they will be when it comes to treating a patient from visit to visit.
For more information:
- Philip J. Rosenfeld, MD, PhD, can be reached at Bascom Palmer Institute, University of Miami School of Medicine, 900 NW 17th St., Miami, FL 33163; 305-326-6148; fax: 305-326-6417; e-mail: prosenfeld@med.miami.edu. Dr. Rosenfeld has received travel reimbursement but does not receive research support from Carl Zeiss Meditec.
- Jay S. Duker, MD, can be reached at New England Eye Center, 750 Washington St., Box 450, Boston, MA 02111-1533; 617-636-4604; fax: 617-636-4866; e-mail: jduker@tufts-nemc.org.
This article also appeared in Ocular Surgery News, a SLACK Inc. publication.
Learn more about this topic! Attend PCON's 2-credit course during SECO 2009! Click here for details