COHERENCE COM FULL
Applied to the optic disc it includes its full depth. These OCT-A algorithms produce an image (3mm 2 to 12mm 2) that is segmented, by standard, into four zones: the superficial retinal plexus, the deep retinal plexus, the outer retina and the choriocapillaris. To improve visualization and reduce background noise from normal small eye movements, two averaging methods - split spectrum amplitude decorrelation technique and volume averaging - were developed. Phase variance is related to the emitted light wave properties, and the variation of phase when it intercepts moving objects. The former detects differences in amplitude between two different OCT B-scans. OCT-A employs two methods for motion detection: amplitude decorrelation or phase variance. Longer wavelengths have a deeper tissue penetrance, but a slightly lower axial resolution. Light is emitted through either a spectral domain OCT (SD-OCT), with a wavelength of near 800nm or a swept-source OCT (SS-OCT), which utilizes a longer wavelength, close to 1050nm. with marked changes between scans) and zones with slower, or no flow at all, which will be similar among scans. With OCT-A technology, the same tissue area is repeatedly imaged and differences are analyzed between scans (over time), thus allowing one to detect zones containing high flow rates (i.e. The OCT scan of a patient's retina consists of multiple individual A-scans, which when compiled into a B-scan provides cross-sectional structural information. OCT-A technology uses laser light reflectance of the surface of moving red blood cells to accurately depict vessels through different segmented areas of the eye, thus eliminating the need for intravascular dyes. The first clinical studies using this innovative technology were published in 2014.
Optical coherence tomography angiography (OCT-A) has emerged as a non-invasive technique for imaging the microvasculature of the retina and the choroid. The foveal avascular zone is seen in the center of the macula.
OCT angiogram of a normal eye illustrating detailed microvasculature in the macula.
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