Novel imaging technology provides real-time volumetric visualization

By Cheryl Guttman Krader

Las Vegas-Swept-source, microscope-integrated, ocular coherence tomography (SS-MIOCT) is a new investigational technology for real-time intraoperative imaging of the cornea and anterior segment, said Terry Kim, MD.

The system, which is being developed by researchers at Duke University Eye Center, Durham, NC, provides live, depth-based anatomic information that is expected to be highly useful for monitoring and guiding surgical procedures, said Dr. Kim at Refractive Surgery 2015 during the American Academy of Ophthalmology annual meeting.

“Ophthalmic surgical microscopes provide a top-down view of the surgical field while OCT imaging provides direct depth information,” said Dr. Kim, professor of ophthalmology, Duke University School of Medicine. “Microscope integration of OCT allows for simultaneous surgery and imaging.

“SS-MIOCT adds a new dimension to the surgeon’s intraoperative view, and the results from preliminary evaluation of its clinical applications are very encouraging,” he added.

The system has an A-scan rate of 100 kHz, a volume rate of 2 Hz, an A/B-scan ratio of 500, resolution of 14x14x7.8 µm (x, y, z) and an imaging range of 12x12x7.4 mm (x, y, z).

It provides a volume (three-dimensional; 3-D) image, a B-scan (2-D) image, and a summed voxel projection (top down) image. It is referred to as “4-D” imaging because the technology adds real-time as a fourth dimension to the volumetric image, according to Dr. Kim.

Dr. Kim presented images and videos from early studies evaluating use of SS-MIOCT in patients undergoing cataract surgery, patients undergoing Descemet stripping automated endothelial keratoplasty (DSAEK), and during deep anterior lamellar keratoplasty (DALK) performed in ex vivo human eye bank globes.

Videos from cataract surgery demonstrated how the technology could be used for assessing incision integrity while pressing on the cornea with a Weck-cel sponge. Videos from DSAEK showed the process of graft unfolding and checking of the graft interface. Use of SS-MIOCT revealed a focal graft detachment, and its resolution after rolling with a LASIK flap roller.

Intraoperative evaluation of the DSAEK graft interface can otherwise be confounded by the presence of corneal edema, Dr. Kim noted.

The benefit of real-time depth imaging with SS-MIOCT was demonstrated in the examples from the DALK procedure that highlighted how it allowed visualization of the needle tip within the cornea before injecting air to separate Descemet’s membrane and stroma.

“Using SS-MIOCT, surgeons will be able to maximize the position of the needle to ensure a successful big bubble,” Dr. Kim said.