By Emily Dieckman, College of Engineering
March 9, 2022
Eye infections are common in rural farming communities. A scratch on the cornea caused during agricultural work can become infected and turn into a scar and then an ulcer. These corneal ulcers cause blindness and visual impairment in 4.3 million people worldwide each year, according to data published by The Lancet Global Health.
Existing methods for diagnosing these ulcers can be expensive, invasive and time-consuming, and they are not always accessible to people living in rural areas.
A University of Arizona researcher is working on an alternative: a wearable device he’s creating with the support of a million-dollar grant from the National Eye Institute.
Dongkyun “DK” Kang, an assistant professor of biomedical engineering and optical sciences at UArizona and a member of the university’s BIO5 institute, had developed a smartphone-based confocal microscope for diagnosing rural cancer. Halfway around the world, Jaya Chidambaram, a senior lecturer at the University of Manchester in the UK, was testing a confocal microscope to diagnose corneal ulcers in patients in India.
When Chidambaram heard about Kang’s work, she asked if her low-cost wearable technology could be applied to corneal imaging to make diagnostics faster, more affordable and accessible in rural communities. They worked on a concept to create a portable in vivo confocal ophthalmoscope, or PICO.
“She came with a problem, I came with a solution, and we felt like it was a really good match,” said Kang, principal investigator of the PICO project and head of the Translational Optical Imaging Lab. from UArizona James C. Wyant College of Optical Sciences.
Go beyond invasive imaging
The first-line diagnostic tool for corneal ulcers is a slit lamp – a device used in routine eye exams to shine a slit of light, which the ophthalmologist can move back and forth across the eye. patient’s eye to look for problems. However, even experienced ophthalmologists often cannot determine the origin of an infection from a slit lamp examination alone. Knowing whether the infection is fungal, parasitic, or bacterial is key to effectively treating the ulcer. Today’s gold standard is microbiological testing, which involves scraping a small piece of the cornea and culturing it for several weeks.
It’s not ideal, Kang said.
“This type of exam is not always available in low-resource settings, and if the ulcer is acute, it sometimes progresses even further during that one to two week wait,” he said. “Not to mention that it’s an invasive and painful process for the patient.”
Chidambaram’s clinical trial involved the use of in vivo confocal microscopy to capture images of patients’ eyes. This method is faster, more accurate and less invasive than microbiological tests, but it is not without drawbacks: confocal microscopes are expensive, not portable and require direct contact with the cornea. Although the method offers same-day results, the actual imaging, in which the microscope touches a patient’s already inflamed eye, can take around half an hour.
By teaming up with Kang, Chidambaram hopes to overcome some of these challenges.
Faster scanning of a larger area
The confocal microscopes used now achieve high resolution and contrast by illuminating a single point at a time with laser-focused light. The laser moves over each point to gather information, combines all the data and digitizes it to create a highly detailed image. This high level of resolution is critical, but the mechanical precision required is time-consuming. Doctors can only capture a relatively small area of the image. Eye movement, which is virtually unavoidable when a device touches a patient’s eye, often requires doctors to re-scan certain areas, further lengthening the process. And it’s expensive. Confocal microscopes cost upwards of $75,000, which severely limits their use in rural clinics.
The key to the technology Kang and Chidambaram are working on is that it scans in two dimensions rather than one – line by line, rather than point by point. The PICO device uses a diffraction grating to scatter the light source into different colored wavelengths, similar to what happens when light passes through a prism. Diffraction illuminates a two-dimensional line, rather than a one-dimensional point, so a much larger portion of the eye can be scanned at once without sacrificing image quality.
“We use this diffraction method to scan and illuminate an image in the entire tissue area, without having to scan anything mechanically,” Kang said. “It increases the speed by up to 20 times and reduces the cost by up to eight times.”
Kang estimates the method will take about two minutes. Since the beam does not need to be moved with such mechanical precision, it is also easier to scan a larger area of the eye in one go. And all of this can be done without direct contact with the cornea, reducing risk and discomfort for the patient. Because the device is portable, it also means doctors can bring the technology directly to patients and provide results immediately, rather than a patient needing to make multiple trips to the hospital or doctor’s office.
“We strongly believe that PICO will be adopted as a standard corneal imaging tool, and its availability in a wide range of healthcare settings will fundamentally improve eye care worldwide,” Kang said.
President of the University of Arizona Robert C. Robbinsa heart surgeon, praised Kang and Chidambaram’s efforts.
“This partnership has the potential to transform eye care, especially in rural communities where access to such care may be limited,” he said. “By leveraging existing technology in an innovative way to improve the patient experience, this work speaks directly to the university’s core values of adaptation and compassion. I look forward to following Dr. Kang’s progress in creating a new gold standard for corneal imaging.