• Northwestern Engineering
    Comprehensive Ophthalmology, Retina/Vitreous

    Scientists at Northwestern University have developed a microscopic, transparent device that they incorporated into a contact lens to measure blood flow speed and oxygen metabolic rate at the back of the eye.

    Called the Micro-ring resonator detector, the device builds upon Northwestern Professor Hao F. Zhang’s groundbreaking work in photoacoustic imaging, which combines sound and light waves to create images of biological materials.

    Zhang hopes the imaging technique can be used in both fundamental biological investigations and for the diagnosis of common diseases such as macular degeneration and diabetes.

    “We believe that with this technology, optical ultrasound detection methods will play an increasingly important role in photoacoustic imaging for the retina and many biomedical applications,” Zhang said.

    Zhang and colleagues published their work in the January 2017 issue of Transactions on Biomedical Engineering.

    Their work began with an idea presented to Zhang more than a decade ago. In 2006, Dr. Amani Fawzi, now an associate professor of ophthalmology at Northwestern’s Feinberg School of Medicine, presented the idea of a diagnostic device that could measure biological activities in the posterior segment.

    To meet Fawzi’s challenge, the team had to develop a detector small enough for ocular use, soft enough to be integrated into a contact lens and yet efficient enough to generate super-high resolution images. In other words, a radical shift from the bulky, opaque ultrasound detection devices of that time.

    “We needed a device that had large enough bandwidth for spatial resolution,” Zhang said. “And it needed to be optically transparent to allow light to go through freely.”

    After several attempts, they landed on the idea of a tiny ring implanted in a single-use contact lens worn during diagnosis.

    The resulting plastic Micro-ring resonator is a transparent device that is 60 micrometers in diameter and 1 micron high. It continues to evolve and improve, with support from Northwestern, the National Institutes of Health, Argonne National Laboratory, and the National Science Foundation.

    Scientists from a variety of fields have approached the team about adapting it for their own work. From urologists who want to study the optics of breast cancer cells, to neuroscientists interested in drug protection in the cortex during different points of a stroke.

    Even geologists see the potential for investigating earthquakes and the earth’s crust.

    “Hearing from a geologist—that was a surprise,” Zhang said, adding that the next step is to test the device in humans.