Advances in imaging technology using swept-source microscope-integrated optical coherence tomography (OCT) provides detailed and three-dimensional volume images in real time, which cannot be obtained with conventional spectral-domain intraoperative OCT systems.
Durham, NC-Intrasurgical imaging using a swept-source, microscope-integrated optical coherence tomography (MIOCT) device is the latest advance in OCT technology that has positively impacted intraoperative human retinal imaging during vitreoretinal surgery.
Intraoperative OCT imaging has been pioneered at Duke University, Durham, NC, by a team led by Cynthia Toth, MD, professor of ophthalmology and bioengineering, and Joseph Izatt, PhD, professor of bioengineering.
“The increased speed and tracking of our next-generation swept-source MIOCT device addresses many of the deficiencies of current intraoperative spectral-domain (SD) platforms and enables seamless real-time, three-dimensional (3-D) imaging of instrument-retina interactions for the first time,” said Paul Hahn, MD, PhD, speaking about the swept-source MIOCT prototype unit developed at Duke University.
A number of different types of OCT imaging systems are available for use intraoperatively, but they come with their downsides. A particular handheld SD-OCT instrument (Envisu, Bioptigen) that is approved by the FDA can indeed be used intraoperatively, he noted.
“Much of our current data on intraoperative OCT comes from handheld devices, but they require stopping surgery and therefore cannot obtain real-time OCT images around a moving instrument,” said Dr. Hahn, assistant professor of ophthalmology, Duke Eye Center, Duke University School of Medicine.
(Figure 1) Individual line scans capturing a surgical maneuver (top row) may provide information about retina-instrument interactions but are very difficult to interpret out of context. Real-time 3-D volume scans, acquired with a prototype Duke swept-source, based microscope-integrated OCT system, enable improved visualization and contextual perception. (Figure courtesy of Paul Hahn, MD, PhD)
In addition to the Duke MIOCT unit, other microscope-integrated OCT devices include the Haag-Streit iOCT and the Zeiss RESCAN 700. None of these devices is currently commercially available in the United States.
The major advantage of microscope-integration is the shared optical path with the surgical microscope that enables OCT image acquisition simultaneously with surgical maneuvers. The previous-generation Duke device and all current devices are spectral-domain OCT based, which have allowed visualization of only individual line scans during surgery.
“These individual scans can be very difficult to interpret out of context,” Dr. Hahn said.
Recently, the Duke team finished incorporating next-generation technology into their MIOCT, including use of a swept-source OCT engine to replace the previous spectral-domain engine along with customized tracking hardware and software to target the OCT beam in real -time to a desired area of interest in the retinal tissue.
Dr. Hahn and colleagues obtained MIOCT images concurrently with surgical manipulations in both model eye systems and in human patients undergoing macular surgery using this next-generation device.
“The lightning-fast speed of our swept-source OCT engine allows us to obtain many individual scans in the time it previously took to obtain one,” Dr. Hahn said. “As a result, we can view individual line scans but can now see the retina in three-dimensional volumes in real time-which adds so much more information compared with visualization of a single scan as with other spectral-domain systems,” Dr. Hahn said.
In commenting on the current and future directions, Dr. Hahn said, “MIOCT facilitates an understanding of real-time intrasurgical changes in vitreoretinochoroidal anatomy and their impact on visual outcomes.
“Our next-generation system can push the envelope further, allowing us to develop new surgical techniques and advanced multimodal methods of surgical viewing,” Dr. Hahn said. “As with any new technology, the possibilities are endless.”
Paul Hahn, MD, PhD
This article was adapted from Dr. Hahn’s presentation during the 2014 meeting of the American Society of Retina Specialists. Dr. Hahn has no financial interest in the subject matter.