Doing so may aid physicians' initial diagnosis of glaucoma by indicating areas of generalized thinning or focal defects, and it has the potential to assist with follow-up progression analysis as well. Moreover, operators can create thickness maps of retinal regions of interest by segmenting the RNFL on each frame of the 3-D data cube (Figure 2). Such an advance would enhance the longitudinal evaluation of glaucoma patients and glaucoma suspects. The new capabilities afforded by 3-D imaging may facilitate image registration, which could lead to more reliable and consistent measurements over time. It is also possible to go back to a 3-D data cube to extract scanning patterns (eg, the 3.4-mm circumpapillary scan) after an imaging session has occurred. Operators may use these images to evaluate ocular motion that occurred during the scan.
#Spectral domain optical coherence tomography software
After acquiring a 3-D data cube, SDOCT software can sum the tissue-reflectance values along individual A-scans to create an OCT fundus (en-face) image (Figure 1). The 3-D data volumes of tissue obtained by raster scanning offer several unique advantages compared with traditional scanning methods. In addition, faster scanning makes possible the acquisition of new scanning patterns, including three-dimensional raster data sets (also referred to as 3-D data cubes), comprising volumes of tissue. Averaging multiple scans reduces the image's noise level and may improve the quality of the scan. Alternatively, users can rapidly acquire repeated scans at a given location. The quickness with which these scans can be obtained minimizes the effect of ocular movements. The drastic increases in scanning speed with SDOCT facilitate the rapid acquisition of scanning patterns, such as the 3.4-mm circumpapillary scan used to characterize the retinal nerve fiber layer's (RNFL) thickness in time-domain OCT. What applications might SDOCT have in glaucoma? For this reason, SDOCT can obtain images much faster-more than 100 times faster in some systems-than time-domain OCT. Information on depth is transformed from the frequency domain to the time domain, and a moving reference mirror is not necessary to obtain complete A-scans. These machines acquire entire A-scans in one instance by measuring frequency components of reflected light at a given point in tissue. In the past 2 years, the FDA has approved several Fourier/spectral domain OCT (SDOCT) imaging devices. Time-domain OCT imaging has been commercially available for almost a decade and has become the cornerstone for retinal imaging. OCT B-scans are generated by acquiring several neighboring A-scans. In time-domain OCT imaging, tissue-reflectance information in depth (an A-scan) is gradually built up over time by moving a mirror in the reference arm of the interferometer. Optical coherence tomography (OCT) uses low-coherence interferometery to obtain cross-sectional images of ocular structures such as the retina, optic nerve, and cornea.
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