A new hand-held retinal scanner was designed to be quickly and easily 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.