Novel imaging technology provides real-time volumetric visualization for cataract and cornea surgeons

Take-home message: Swept-source microscope-integrated ocular coherence tomography is an investigational real-time imaging technique for monitoring and guiding anterior segment procedures.

Reviewed by Terry Kim, MD 

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

The technology provides live, depth-based anatomic information that is expected to be highly useful for monitoring and guiding surgical procedures. The system is being developed by a team of researchers led by Joseph Izatt, PhD, professor of biomedical engineering and ophthalmology, and Cynthia Toth, MD, professor of ophthalmology and biomedical engineering, Duke University Eye Center, Durham, NC.

“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,” Dr. Kim 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.

Impressive images

Impressive images

Dr. Kim presented images and videos from early studies with Anthony Kuo, MD, assistant professor of ophthalmology, Duke University, 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 taken during 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, noted Dr. Kim, who is also chief, cornea and external disease division director, refractive surgery service, Duke University Eye Center.

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.

Terry Kim, MD

E: terry.kim@dm.duke.edu

This article was adapted from Dr. Kim’s presentation during Refractive Surgery Subspecialty Day at the 2015 meeting of the American Academy of Ophthalmology. Dr. Izatt and Dr. Toth are co-authors on a patent for MIOCT held by Duke University. Dr. Kim and Dr. Kuo have no relevant financial interests to report.