McKelvey School of Engineering Neurotechnologies

New technology offers faster, broader 3D imaging of retinas, feasibility study shows

A volumetric render of the retina from a healthy volunteer acquired using the SDM-OCT instrument. Wide-field 3D images covering a 12.5 mm×7.4 mm region were acquired in less than 1 second. (Image: Zhou lab)

Each year, more than 30 million people have their eyes scanned using optical coherence tomography (OCT) to detect for diseases of the retina, such as age-related macular degeneration and diabetic retinopathy. While OCT takes excellent images, it is very sensitive to any movement — even breathing — by the patient, and is limited to a specific region of the eye. A team of biomedical engineers in the McKelvey School of Engineering at Washington University in St. Louis has performed a clinical feasibility study on a new technique that is at least 10 times faster than existing OCT scanners, which creates fewer opportunities for errors from patient movement and allows for earlier detection and treatment of eye diseases.

Chao Zhou, associate professor of biomedical engineering, led a team in testing a light-splitting technique known as space-division multiplexing (SDM) that takes four high-definition OCT images simultaneously with a single detector. Working with ophthalmologists at the Scheie Eye Institute at the Penn Presbyterian Medical Center at the University of Pennsylvania, Zhou and doctoral student Jason Jerwick tested the technique on 10 patients ages 18-80 with retinal disease and were able to acquire images in a wider field than existing OCT scanner in less than 1 second. The results of the feasibility study are published in Photonics Research April 1.

Because of limitations on imaging speed, the existing OCT scanners can only take an image from a limited region of the retina, which may result in missed defects or disease in the peripheral retina and an incorrect diagnosis. To address this, Zhou and Jerwick built a prototype system, which looks similar to equipment used for a regular eye exam. For the SDM-OCT scan, the patient places his or her chin on a chin rest and leans forward so that the laser beam can scan much more of the eye at a resolution of about 7 micron, or seven-millionths of a meter. The exposure has minimal risk to any damage to the eye.

The prototype used fiber-based splitters to facilitate the parallel imaging that allowed them to get four images without overlapping. Then, they stitched the images together to get a high-definition, 3D image.

“We can get similar image quality with a much higher speed and the wider field of coverage so that we can detect the peripheral disease more effectively and at an earlier stage,” Zhou said.

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