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Real-time imaging adds interactive dimension to vitreoretinal surgery, training
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First introduced in the early 1990s, OCT is a noninvasive imaging technique that obtains high-resolution, cross-sectional images of the retina and other ophthalmic tissues.
In recent years, this technology has transitioned from being only available in the clinic to being able to be utilized in the operating room. Intraoperative OCT has allowed ophthalmologists to access real-time imaging of vitreoretinal surgery for the first time, adding a new dimension to surgery and education, according to a 2016 study published in Eye (London) by Justis P. Ehlers, MD.
There are several FDA-approved systems with optional add-ons to improve performance. Companies such as Leica, Carl Zeiss Meditec and Haag-Streit have developed systems for ophthalmologists to obtain and utilize real-time intraoperative images of their procedures.
Improvements in imaging
Since the early 2000s, technology has been developed to gather clinical images of the retina, such as fluorescein angiography, fundus photography, widefield imaging, OCT and OCT angiography, OSN Retina/Vitreous Board Member Seenu M. Hariprasad, MD, said.
Image: Hariprasad SM
However, when performing vitreoretinal surgery, there is a “complete disconnect” with these useful in-office technologies, he said.
“When I take a patient to the operating room, it’s a complete digital cutoff. I have a few still images that I printed out in my office to take to the operating room, but they’re not dynamic, but rather just a rough indication of what’s going on. It’s not live. It’s not dynamic. It’s not that useful beyond the ability to confirm that the patient has a certain diagnosis,” he said.
But now, with the development of intraoperative OCT systems, Hariprasad said ophthalmologists have the ability to image the eye in “real time” to assist the surgeon in various ways and enhance the educational experience for trainees.
An added dimension
The technology adds another dimension to vitreoretinal surgery and can help the surgeon in various ways. For example, during a tractional retinal detachment case, the EnFocus Leica intraoperative OCT unit can help delineate tissue planes and identify point adhesions between pathologic membranes and the retina, Hariprasad said.
“These technologies bring OCT imaging technology into the operating room setting. When I’m doing vitrectomy surgery for an epiretinal membrane, for example, and I want to take an optical slice of the retina, I just click a button and the machine starts scanning. I can see the epiretinal membrane as I would in my office. As I pinch the membrane to peel it away with my forceps, I can in real time see if I am applying too much traction to the retina as I peel the membrane off of the surface of the retina. After membrane peeling is completed, I can reimage to see whether I completely peeled the epiretinal membrane. Intraoperative OCT adds another dimension to surgery,” Hariprasad said.
The first step into intraoperative OCT technology was portable devices, with the Envisu (Bioptigen/Leica) and the iVue (Optovue) being the first two portable systems developed, according to a 2015 study by Ehlers and colleagues.
The hand-held devices enabled surgeons to take high-quality images during a procedure, but the surgery had to be halted for the pictures to be taken, so the devices lacked a real-time imaging aspect.
“When OCT was first developed, the definitive role for OCT was unclear. However, over time the use of OCT in our clinics has revolutionized our approach to disease diagnosis, treatment surveillance and clinical decision-making. The use of OCT in the operating room is still in its early stages. As the technology advances, its role in ophthalmic surgery will also evolve,” Ehlers said.
Microscope-integrated systems
The technology has evolved, and several companies integrated microscope optics into their OCT systems. Early prototype research systems demonstrated the feasibility of this technology. Integrating OCT and the microscope provided surgeons the first “real-time” OCT imaging during surgery. Prototypes with multiple microscopes and OCT systems have been described, according to Ehlers’ study.
Building on to this early research technology, Carl Zeiss Meditec developed the Rescan 700, the first FDA-approved intraoperative OCT system in 2014 and the second system to be available worldwide. The system is built on a Lumera 700 microscope platform and includes a heads-up display to provide surgeons with visualization of the OCT data stream and surgical field, according to Ehlers’ study.
In 2015, Leica received FDA approval for its EnFocus intrasurgical OCT system, which allows visualization of ocular tissue microstructure during ophthalmic surgery in high resolution, according to a 2015 press release from the company.
Ehlers said that his research group has utilized both systems. Each one offers advantages when used during different types of ocular surgeries, he said.
“We currently have multiple microscope-integrated intraoperative OCT systems that we utilize, including the Zeiss Rescan 700 and the Leica EnFocus. In addition, we have an external microscope-mounted system that is also used. There have been significant advantages to integrating the OCT technology into the microscope, including image acquisition efficiency, the ability to image rapidly in the area of interest, allowing for real-time OCT during tissue manipulation,” Ehlers said.
Haag-Streit designed its own system, the iOCT, which was the first globally commercially available system, approved by the FDA in 2015. The system uses a modular OCT scanner attached to a camera port of the microscope, according to a study published in Biomedical Optics Express in 2017.
DISCOVER and PIONEER studies
Two studies were conducted by Ehlers and colleagues to determine the implications and performance of microscope-integrated OCT systems, including the Rescan 700 and EnFocus intraoperative OCT systems in ophthalmic surgery.
The DISCOVER study, which had its first-year results published in 2015, evaluated 227 eyes, 91 anterior segment cases and 136 posterior segment cases, in the first year and has now enrolled more than 1,000 cases.
The PIONEER study, published in 2014, assessed intraoperative OCT imaging on 531 eyes that underwent various ophthalmic procedures.
Both large-scale, prospective studies evaluated the impact of intraoperative OCT on surgical decision-making, Ehlers said.
“The PIONEER study evaluated a microscope-mounted system. The DISCOVER study is still ongoing and utilizes various microscope-integrated systems. These studies demonstrated the potential significant impact of intraoperative OCT on surgical decision-making. Overall, intraoperative OCT appears to impact surgical decision-making in 20% to 30% of cases. These results strongly suggest that adding OCT to our intraoperative data stream adds more information to the surgeon than the microscope view alone. More research is needed, as outlined above, to better define how this information impacts outcomes,” he said.
Advantages yet to be defined
The technology is not yet seamless and in some cases may be disruptive, Darius M. Moshfeghi, MD, said.
Moshfeghi, who has used the Zeiss Rescan system in his practice, believes the role for intraoperative OCT has “yet to be defined.”
“I find right now that when I use it, it slows me down. That’s because the technology is not designed for inline surgical operating. I have to switch off my viewing system, bring in the technology, and it can be slow turning on. You need to see if you’re connected, if you’re in the right area, if you’re in focus. Doing all of that, in a situation where oftentimes you’re using it and you have a critical question to ask, the last thing you want is to be futzing around with making the system work to give you the answer. That only adds to your consternation,” he said.
Possible pediatric advantages
Despite not having access to the technology for his pediatric patients, Moshfeghi said he envisions intraoperative technology having a big impact on difficult pediatric cases in which the biology of a patient is not entirely clear.
The technology may be useful for pediatric patients who have a “lot of separation” and physicians may not know “where the membranes are in relation to the underlying retina,” he said.
“It would be very nice to have a tool that works seamlessly and easily, without having to switch back and forth between a traditional viewing system and the OCT viewing system,” he said.
From his own experience, intraoperative OCT offers visualization advantages when used in a pediatric setting, Scott Oliver, MD, said. Oliver noted that he has experience with both the EnFocus and Rescan systems in his adult and pediatric operating rooms and that the EnFocus offers good resolution during surgery.
“For pediatric retina cases, I find that I can steer the intraoperative OCT image more effectively than hand-held OCT. This works to confirm a tiny retinoblastoma tumor, to see if there really is a shallow tractional retinal detachment from retinopathy of prematurity or to distinguish thickened retina from detached retina in Coats’ disease. Even for nonincisional cases, intraoperative OCT has a role,” he said.
Current drawbacks
Intraoperative OCT technology may one day change the field of ophthalmology, but it still has some drawbacks, OSN Retina/Vitreous Section Editor Andrew A. Moshfeghi, MD, MBA, said.
Moshfeghi has used intraoperative OCT for vitreoretinal surgery in the context of an extended demo of the Zeiss product at the USC Roski Eye Institute. It was helpful to confirm release of traction after vitrectomy with internal limiting membrane peeling for full-thickness macular hole with persistent vitreomacular traction as well as several other macular cases, he said.
“This technology does have the potential to change the field of ophthalmology one day, but I’m not sure that day is now. One drawback of the system for vitreoretinal surgeons is that it is primarily useful for evaluating the posterior pole. One unmet need for vitreoretinal surgeons, however, is OCT imaging of the far peripheral retina, both in the clinic and intraoperatively. While hand-held systems can aid in this analysis, they suffer from image stabilization issues, are heavy on the eye and lack the high-resolution image capability we are used to with the office-based systems that evaluate the macula,” he said.
The Zeiss system also has drawbacks during surgery, Moshfeghi said. While it is noncontact, the system is coaxially situated with the surgeon’s view and cannot be angled to image the far peripheral retina on demand.
“Having the ability to direct a noncontact intraoperative OCT system to the pre-equatorial retina may significantly increase its pragmatic application for vitreoretinal surgeons dealing with complex peripheral pathology such as combined retinoschisis-rhegmatogenous retinal detachments, retinopathy of prematurity-related retinal detachments in immature and phakic eyes, as well as targeting areas of suspected retinal detachment whose clinical assessment may be equivocal for definitive subretinal fluid,” he said.
Educational possibilities
Currently, the technology and the various systems may offer more educational opportunities than surgical advantages, Oliver said.
“It will definitely change retina surgical training. Fellows will get real-time feedback as they learn to identify membrane layers and perform their first membrane peels,” he said.
For experienced retina surgeons, intraoperative OCT technology will be more useful for adding insight where current visualization technology falls short, such as complex pathology in the periphery.
Hariprasad said he has used his system to show surgical retina fellows what he is doing in real time. The technology also gives them the ability to see vitreoretinal disease in a “different way than they ever had in the past. They understand surgical concepts more clearly, especially in tractional retinal detachment cases.”
The value of the technology for trainees is key, he said, as they can see the pathology from two different perspectives: one through the operating microscope oculars and the other on the display of the intraoperative OCT machine.
“For example, when I ask them during a tractional retinal detachment case to cut between the point adhesions and try to find planes that are safe to cut with the vitrectomy cutter, I can now actually show them in real time. Turn your head, look at the screen, see those two vertical point adhesions? Those are the two columns that are attaching the retina to the scar tissue — I want you to cut between those two point adhesions. With our intraoperative OCT machine, they can now visualize what I’m saying. Once they are done with the segmentation of the membranes, we reimage and they can see that they successfully cut the membrane without damaging the retina,” Hariprasad said.
The technology can help residents improve their surgical skills and outcomes for certain ophthalmic procedures, according to studies in the literature. For example, ophthalmology residents using microscope-integrated OCT technology during select anterior segment surgical maneuvers on porcine eyes outperformed residents who operated on porcine eyes without microscope-integrated OCT technology, according to a 2016 study published in Investigative Ophthalmology and Visual Science.
According to the study, residents who operated on porcine eyes with a microscope-integrated OCT system outperformed residents who did not use OCT technology during depth-based anterior segment maneuvers.
The enhanced performance continued when residents who had previously used the microscope-integrated OCT technology during their procedures had the technology taken away. Researchers suggested that the technology may allow for sustained learning of a surgical skill even when real-time feedback is not available.
Despite its potential advantages, the technology must see a reduction in cost and an increase of ease of use to become widespread throughout ophthalmology, Oliver said.
“There are two main barriers: cost and ease of use. Once cost comes down, widespread adoption will depend on a user interface that does not interrupt normal surgical workflow. Integrated visualization of the OCT with the microscope image, surgeon steerability even outside the arcades and high resolution are all top priorities,” he said.
Gone are the days of a single preoperative OCT image that surgeons use for all of their decisions in the operating room, Oliver said. Just as clinic-based OCT taught surgeons a great deal about the macula, intraoperative OCT will give dynamic information about the retina as it is being repaired in real time. – by Robert Linnehan
- References:
- Carrasco-Zevallos OM, et al. Biomed Opt Express. 2017;doi:10.1364/BOE.8.001607.
- Ehlers JP. Eye (Lond). 2016;doi:10.1038/eye.2015.255.
- Ehlers JP, et al. Am J Ophthalmol. 2014;doi:10.1016/j.ajo.2014.07.034.
- Ehlers JP, et al. JAMA Ophthalmol. 2015;doi:10.1001/jamaophthalmol.2015.2376.
- Leica receives FDA approval for EnFocus OCT. https://www.leica-microsystems.com/news-media/news-events/news-details/article/leica-receives-fda-approval-for-enfocus-oct/News/detail/. Published Dec. 14, 2015. Accessed June 19, 2017.
- Todorich B, et al. Invest Ophthalmol Vis Sci. 2016;doi:10.1167/iovs.15-18818.
- For more information:
- Justis P. Ehlers, MD, can be reached at Cole Eye Institute, Cleveland Clinic, 9500 Euclid Ave., i30, Cleveland, OH 44195; email: ehlersj@ccf.org.
- Seenu M. Hariprasad, MD, can be reached at University of Chicago Medicine and Biological Sciences, 5841 S. Maryland Ave., MC2114, Chicago, IL 60637; email: retina@uchicago.edu.
- Andrew A. Moshfeghi, MD, MBA, can be reached at USC Roski Eye Institute, Keck School of Medicine, University of Southern California, 1450 San Pablo St., 4th Floor, Los Angeles, CA 90033; email: amoshfeghi@gmail.com.
- Darius M. Moshfeghi, MD, can be reached at Byers Eye Institute, Stanford University of School of Medicine, 2452 Watson Court, Palo Alto, CA 94303; email: dariusm@stanford.edu.
- Scott Oliver, MD, can be reached at University of Colorado School of Medicine, 1675 N. Aurora Court, Stop F731, Aurora, CO 80045; email: scott.oliver@ucdenver.edu.
Disclosures: Ehlers reports he is a consultant for Zeiss, Leica and Alcon; has intellectual property licensed to Leica; and has received research support or equipment support from Leica, Zeiss and Alcon. Hariprasad reports he is a consultant for Leica and Alcon. Andrew Moshfeghi reports no relevant financial disclosures. Darius Moshfeghi reports he was previously a consultant for Alcon. Oliver reports no relevant financial disclosures.
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