If you're like a lot of people, you don't make an annual trip to the ophthalmologist to get your eyes checked ... and you really ought to, in order to catch any problems before it's too late. If it were possible to get them checked at a regular doctor's office or clinic, though, perhaps you might do so more often. That's one of the reasons that a team at MIT have designed a new hand-held retinal scanner, that can quickly and easily be used anywhere.

Ordinarily, eye exams are carried out using relatively large instruments that are permanently located in an optometrist or ophthalmologist's office. The portable prototype MIT device, by contrast, is about the size of a consumer camcorder. It can "read" a patient's eye in seconds, using a single measurement to look for conditions such as diabetic retinopathy, glaucoma and macular degeneration.

It utilizes an existing technique known as optical coherence tomography (OCT), in which beams of infrared light are shone onto the retina. By measuring both how long it takes those beams to reflect back, and the intensity of those reflections, the scanner is able to build up a radar-like 3D image of the retina. It's the same technology used by the traditional larger scanners, although the development of a miniaturized mirror for scanning the imaging beam allows it to be used in the new device.

One challenge with a hand-held scanner is the fact that the user's shakes could result in blurred images. To correct for that, the MIT device quickly performs several scans of the same part of the retina, from different directions. Those scans are then combined to form one composite three-dimensional image, with any details that are missed in one scan being caught by another. The system can also compensate for unintentional movements of the patient's eye.

Other portable retinal scanners do already exist, although this feature – along with the high-speed 3D scanning and the miniaturized mirror – are said to be unique to this prototype.

Two versions of the device have been lab-tested, and found to produce results similar in quality to those of traditional larger OCT scanners. It is hoped that once developed further, the smaller scanners could be used not only in regular doctors' offices but also in developing nations, where the regular equipment simply isn't available. Before that can happen, however, additional research will be required to bring down the cost of the device.

MIT collaborated with Praevium/Thorlabs and Germany's University of Erlangen on the research, which is outlined in a paper recently published in the journal Biomedical Optics Express.

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