Application of iOCT to ophthalmic surgery: Pioneer 18-month results

Take-Home

PIONEER study results find that intraoperative optical coherence tomography is vital for vitreoretinal surgery and recovery.

By Michelle Dalton, ELS; Reviewed by Justis P. Ehlers, MD

Cleveland-Optical coherence tomography (OCT) can be successfully used during vitreoretinal surgery and can provide significant information about various milestones throughout the surgery, said Justis P. Ehlers, MD.

“Anatomic visualization with intraoperative OCT (iOCT) provides live feedback to the surgeon,” said Dr. Ehlers, assistant professor, Vitreoretinal Service, Cole Eye Institute, Cleveland Clinic. “It’s a unique opportunity to understand the underlying pathophysiology of surgical ophthalmic diseases.”

The Prospective Intraoperative and Perioperative Ophthalmic ImagiNg with Optical CoherEncE TomogRaphy (PIONEER) Study prospectively enrolled 394 eyes of patients undergoing ophthalmic surgery to assess its feasibility and use in anterior and vitreoretinal surgery, Dr. Ehlers said.

The study

Of those 394 eyes, 196 were vitreoretinal surgeries, most of which were for macular surgical diseases.

Over the course of the first 18 months of the ongoing study, six vitreoretinal surgeons and five anterior segment surgeons used a microscope-mounted portable spectral-domain OCT probe (Envisu SDOIS, Bioptigen) to acquire images during the surgeries (see figure).

Most eyes (n = 149; 76%) were pseudophakic; 40 eyes (20%) were phakic and seven eyes (4%) were aphakic.

In the vitreoretinal arm of the study, epiretinal membrane and full thickness macular hole were the most frequent indications with 73 eyes (37%) and 42 eyes (21%), respectively.

Other diagnoses included retinal detachment and proliferative diabetic retinopathy/traction retinal detachment (31 and 27 eyes, respectively). The remaining eyes underwent surgery for vitreomacular traction, vitreous hemorrhage, subretinal hemorrhage, and endophthalmitis.

Successful iOCT imaging was obtained in 188 eyes (96%), and added anywhere from 65 seconds to 4 minutes to the procedure.

“Using the microscope-mounted system, the surgeon would stop surgery, position the device for aiming, and acquire the image,” Dr. Ehlers said. “In the future, utilizing a microscope integrated system, the surgeon could potentially image without even stopping the surgery.”

The PIONEER investigators obtained multiple images at each session, and it typically required about 65 seconds to position, aim, and acquire the first image, Dr. Ehlers said.

Although adverse events occurred during the various surgeries (e.g., elevated IOP), none was determined to be specifically related to the OCT scan acquisition, Dr. Ehlers said.

Real-world feedback

Using a surgeon feedback questionnaire, it was determined that if the surgeon was unsure if membrane peeling was complete, iOCT gave the definitive answer in 97% of cases, Dr. Ehlers said.

In the cases where surgeons believed the surgical objectives were achieved and membrane peeling was complete, iOCT revealed residual membranes that the surgeons determined required peeling due to foveal proximity in 8% of cases, he said.

Novel findings included:

·      Subclinical alterations in the foveal architecture.

·      Increased subretinal hyporeflectivity following ILM peeling.

·      Focal architectural changes at the surgical manipulation site.

Analysis of the iOCT images showed significant expansion in the subretinal hyporeflective band following membrane peeling, suggesting increased distance between the ellipsoid zone (i.e., IS/OS junction) and the retinal pigment epithelium, Dr. Ehlers said.

The system utilized for PIONEER was a SD-OCT engine.

Time-domain OCT has both quality and speed issues, Dr. Ehlers said, making it of limited utility for the purposes of this study.

“(However), swept source OCT may have a significant role in the future and we are actively looking at this in our research labs at the Ophthalmic Imaging Center at Cleveland Clinic and through a collaborative biomedical research partnership NIH grant with Duke University in partnership with Cynthia Toth, MD, and Joseph Izatt, PhD,” he said.

“Swept source would provide an even better acquisition speed, as well as a much greater scan depth that allows for visualization, not only at the retinal surface but also in the vitreous, “ Dr. Ehlers said, “which may be particularly useful for intraoperative applications, such as visualizing instrument-tissue interactions.”

Complications

PIONEER does have some limitations, he added.

As it currently exists, the OCT system-though mounted on the microscope-is optically separate from the microscope, which does not allow for the visualization of the instrument-tissue interaction, he said.

“The Cole Eye iOCT research team, including Yuankai Tao, PhD, has developed an integrated system that is currently undergoing laboratory testing,” he said.

“(Clearly), more research is needed to delineate functional and anatomic correlates and surgical outcomes,” Dr. Ehlers said.

However, plans are under way for disease-specific iOCT studies at the Cole Eye Institute to better inform clinicians on the role for iOCT in optimizing patient care, he said.

Justis P. Ehlers, MD

P: 216/636-0183

Dr. Ehlers receives royalties and has intellectual property rights with Bioptigen.

CAPTIONS:

Figure 1: Photograph of microscope mounted handheld Bioptigen spectral domain optical coherence tomography system (red circle).

Figure 2: Three-dimensional reconstruction of vitreomacular traction intraoperative OCT scan revealing the configuration immediately prior to lifting the hyaloid (gray) and immediately after removing the hyaloid (red overlay). Prominent foveal traction is noted with vitreous traction (yellow arrow). Following release of traction there is decrease in central foveal thickness (orange arrow) and continuity of the inner retinal contour (white).

Figure 3: Intraoperative OCT showing prominent epiretinal membrane prior to peeling (red arrow). Following membrane peeling expansion of the IS/OS (i.e., ellipsoid zone) to retinal pigment epithelial distance is noted with increased subretinal hyporeflectivity (yellow arrows). Residual membrane is noted at the optic nerve head (orange).

(Images courtesy of Justis P. Ehlers, MD)

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