News ID: 254987
Published: 1219 GMT June 29, 2019

Low-cost retinal scanner could help prevent blindness worldwide

Low-cost retinal scanner could help  prevent blindness worldwide

Biomedical engineers at Duke University have developed a low-cost, portable optical coherence tomography (OCT) scanner that promises to bring the vision-saving technology to underserved regions throughout the United States and abroad.

Thanks to a redesigned, 3-D-printed spectrometer, the scanner is 15 times lighter and smaller than current commercial systems and is made from parts costing less than a tenth the retail price of commercial systems — all without sacrificing imaging quality.

In its first clinical trial, the new OCT scanner produced images of 120 retinas that were 95 percent as sharp as those taken by current commercial systems, which was sufficient for accurate clinical diagnosis.

The results appear online on June 28 in Translational Vision Science and Technology, an ARVO journal.

In use since the 1990s, OCT imaging has become the standard of care for the diagnosis of many retinal diseases including macular degeneration and diabetic retinopathy, as well as for glaucoma. However, OCT is rarely included as part of a standard screening exam since machines can cost more than $100,000 — meaning that usually only larger eye centers have them.

"Once you have lost vision, it's very difficult to get it back, so the key to preventing blindness is early detection," said Adam Wax, professor of biomedical engineering at Duke. "Our goal is to make OCT drastically less expensive so more clinics can afford the devices, especially in global health settings."

OCT is the optical analogue of ultrasound, which works by sending sound waves into tissues and measuring how long they take to come back. But because light is so much faster than sound, measuring time is more difficult. To time the light waves bouncing back from the tissue being scanned, OCT devices use a spectrometer to determine how much their phase has shifted compared to identical light waves that have travelled the same distance but have not interacted with tissue.

The primary technology enabling the smaller, less expensive OCT device is a new type of spectrometer designed by Wax and his former graduate student Sanghoon Kim. Traditional spectrometers are made mostly of precisely cut metal components and direct light through a series of lenses, mirrors and diffraction slits shaped like a W. While this setup provides a high degree of accuracy, slight mechanical shifts caused by bumps or even temperature changes can create misalignments.

Wax's design, however, takes the light on a circular path within a housing made mostly from 3-D-printed plastic. Because the spectrometer light path is circular, any expansions or contractions due to temperature changes occur symmetrically, balancing themselves out to keep the optical elements aligned. The device also uses a larger detector at the end of the light's journey to make misalignments less likely.

Traditional OCT machines weigh more than 60 pounds, take up an entire desk and cost anywhere between $50,000 and $120,000. The new OCT device weighs four pounds, is about the size of a lunch box and, Wax expects, will be sold for less than $15,000.

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