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Editors Selection IGR 24-3
OCT: Signal-to-noise ratio
Comment by Chris Leung on:
23393 Signal strength is an important determinant of accuracy of nerve fiber layer thickness measurement by optical coherence tomography, Wu Z; Huang J; Dustin L et al., Journal of Glaucoma, 2009; 18: 213-216
OCT Signal-to-noise ratio Comment by Christopher Leung, Hongkong Minimizing RNFL measurement variability is important for reliable detection of progressive loss of the RNFL. Using the Stratus OCT, Wu et al. (191) demonstrated that signal strength, a parameter with a scale from 1 to 10 representing the signal-to-noise ratio and signal uniformity within a scan, contributed significantly to RNFL measurement variability.They found that higher signal strength was associated with greater RNFL thickness if the signal strength was less than 7. While a signal strength of at least 5 is recommended by the manufacturer, there is no consensus on signal strength requirement for RNFL imaging. Wu et al. suggested a signal strength of at least 7 was required. This finding, however, should be interpreted with reference to the fact that most images (79%) analyzed in the study had signal strength less than 8. In an earlier study by Cheung et al. (Ophthalmology 2008; 115: 1347-1351), series of OCT images were obtained with signal strength from 5 to 10. Significant differences were found between RNFL measurements obtained at signal strength of 10 and those obtained with signal strength less than 10. The relationship between RNFL thickness and signal strength was essentially linear. Obtaining maximal possible signal strength is desirable for detecting RNFL damage and its progression.
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