An adaptation of OCT put into use at Northwestern University, visible OCT (vis-OCT), will be a key component in an Advanced Research Projects Agency for Health (ARPA-H)-funded project that aims to conduct successful eye transplants in the next several years. The technology will be used to examine the structural integrity of eyes in donors, such as the health of retinal layers and the flow of blood as well as monitoring their continued viability throughout the process.
This work will be supported by over $50 million in ARPA-H funds to multiple institutions, earmarked for viability, imaging, surgical, immunomodulation, ocular preservation, and neuroregeneration strategies within the Transplantation of Human Eye Allografts (THEA) project. The Northwestern team, led by Hao Zhang, a professor of biomedical engineering, and Cheng Sun, a professor of mechanical engineering, will be part of group directed by Jeffrey Goldberg, professor and chair of ophthalmology at the Byers Eye Institute at Stanford University.
A variation of OCT, vis-OCT, will be integral to a six-year project led by Stanford University aimed at enabling successful eye transplantation. Courtesy of ARPA-H.
Traditionally, OCT systems that are commonly used in ophthalmological applications utilize NIR light. But the use of visible light (provided in most cases by a supercontinuum laser or swept-source laser), can improve axial resolution as well as provide enhanced contrast to examine fine details in tissue layers. As Zhang related in a feature article in BioPhotonics magazine in 2019, vis-OCT can reveal important health metrics, such as retinal hemoglobin oxygen saturation.
Opticent Health, a spinoff company of Zhang’s lab at Northwestern, created the Halo 375 for animal research and the Aurora X4 for human research. These center on a vis-OCT system that includes a supercontinuum white light laser based on photonic crystals, fundus camera for fast imaging, an adjustable field of view, and software to analyze the generated data. It has not yet been approved by the FDA, but is in use for clinical research.
“At this point, we have created the system, it is about overcoming logistical issues associated with this project,” Zhang said. “We have to adapt it for a robotic arm and account for multiple instruments at the bedside. A traditional OCT instrument is used with a chin rest when the patient is sitting, but obviously that wouldn’t work for something like this.”
He said the ARPA-H funding includes expectations of meeting certain guidelines, such as a system ready for use in a medical setting within the next two years, and a clinical protocol within the next three years.
Eye transplants are not new, as more than 70,000 people in the U.S. donate their eyes each year when they die. But these historically have involved corneal transplants, whereas the most common forms of vision loss are caused by retinal degeneration. That is where the whole-eye transplants fit into global eye health. And Zhang acknowledged the questions that need to be answered go beyond the imaging itself.
“With a whole-eye transplant you would need to look at how the muscles attach and whether the blood will flow as it should,” he said. “Then there’s the question of attaching and regenerating the nerves. But I know there are lots of people working on that part of the problem, too.”