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Optical coherence tomography (OCT) scanning systems designed to obtain cross-sectional images of eye (i.e., ophthalmic) tissues. These systems typically consist of a computerized unit that includes a light source, a photodetector, and a display. The light beam (usually in the infrared range) is divided into two beams, one directed towards the sample and the other towards a moving reference mirror. Tomographic images are then obtained by detecting the interference between the light reflected by both beams. The images obtained can show tissue about two or three mm (0.08 to 0.12 inch) in depth and provide axial and lateral resolution in the order of micrometers. The systems reveal the underlying structure not directly observable (tomographic images) in an analogous way, but with higher image resolution than conventional B-mode ultrasound and magnetic resonance imaging. Systems that use light sources at different frequencies simultaneously (spectral domain systems), rather than a mechanical movement of a mirror, are also available. OCT ophthalmic scanning systems are used for a variety of clinical applications involving accurate retinal and intraretinal thickness measurements.
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