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New Scanning Tool may Provide Early Detection for Blinding Eye Disease

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A new optical device has the ability to detect eye disease in the palm of a hand. The tool, which is about the size of a hand-held camcorder, scans a patient's entire retina in mere seconds and could significantly help primary care physicians in the early detection of a slew of retinal diseases including diabetic retinopathy, glaucoma, and macular degeneration.

Researchers at the Massachusetts Institute of Technology (MIT) describe their new ophthalmic-screening instrument in a paper published in the open-access journal Biomedical Optics Express, published by The Optical Society (OSA).

Albeit other research groups and companies have created hand-held devices using similar technology, the new design is the first to join state of the art technologies such as ultrahigh-speed 3-D imaging, a tiny micro-electro-mechanical systems (MEMS) mirror for scanning, and a method to correct for unintentional movement by the patient. These inventions, the authors note, should enable physicians to gather comprehensive data with just one measurement.

Usually, to diagnose retinal diseases, an ophthalmologist or optometrist must inspect the patient in his or her office, normally with table-top instruments. However, few people visit these specialists on a constant basis. Therefore, in order to improve public access to eye care, the MIT research group, in cooperation with the University of Erlangen and Praevium/Thorlabs, has developed a portable device that can be transported and used outside a specialist's office.

"Hand-held instruments can enable screening a wider population outside the traditional points of care. For instance, they can be used at a primary-care physician's office, a pediatrician's office or even in the developing world," said researcher James Fujimoto of MIT, an author on the Biomedical Optics Expresspaper.early detection of blinding

The device uses a procedure called optical coherence tomography (OCT), which the MIT group and collaborators helped forge in the early 1990s. The technology sends beams of infrared light into the eye and onto the retina. Echoes of this light return to the machine, which uses interferometry to measures changes in the time delay and scale of the returning light echoes, revealing the cross sectional tissue structure of the retina, similar to radar or ultrasound imaging. Tabletop OCT imagers have become a traditional form of care in ophthalmology, and current generation hand-held scanners are used for imaging infants and monitoring retinal surgery.

The researchers were able to minimize what has been characteristically a large somewhat cumbersome device into a portable size by using a MEMS mirror to scan the OCT imaging beam. They tested two designs, one of which is similar to a handheld video camera with a flat-screen display. In their tests, the researchers discovered that their device could attain images comparable in quality to standard table-top OCT instruments used by ophthalmologists.

To cope with the motion instability of a hand-held device, the instrument takes multiple 3-D images at high speeds, scanning a specific volume of the eye several times but with different scanning directions. By using multiple 3-D images of the same part of the retina, it is possible to correct for distortions due to motion of the operator's hand or the subject's own eye.

According to Fujimoto, the next stage, is to assess the technology in a clinical environment. However, the device is still relatively expensive and will most likely be some time before this technology finds its way into doctors' offices or in the field, pressuring manufacturers to find a way to support or lower its cost.

“Many people with eye diseases may not even be aware of them until irreversible vision loss occurs. Screening technology is important because many eye diseases should be detected and treated long before any visual symptoms arise. For example, in a 2003 Canadian study of nearly 25,000 people, almost 15 percent were found to have eye disease, even though they showed no visual symptoms and 66.8 percent of them had a best-corrected eyesight of 20/25 or better. Problems with undetected eye disease are exacerbated with the rise of obesity and undiagnosed diabetes. The Center for Disease Control and Prevention estimates that 11.3 percent of the U.S. population over the age of 20 has diabetes, even though many do not know it,” said Fujimoto.

For the coming years, Fujimoto believes that hand-held OCT technology can be applied in many other medical specialties beyond ophthalmology, for instance in applications ranging from surgical guidance to military medicine.

"The hand-held platform allows the diagnosis or screening to be performed in a much wider range of settings. Developing screening methods that are accessible to the larger population could significantly reduce unnecessary vision loss,” he said.

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