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C. Ye, S. Liu, G. W. Lai, L. Liu, C. Y. Cheung, D. S. Lam, C. P. Pang, C. K. Leung; Influence of Multiple B-Scan Averaging on RNFL Thickness Measurement With Spectral Domain Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2010;51(13):253.
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© ARVO (1962-2015); The Authors (2016-present)
To determine whether the number of images used in multiple B-scan averaging would affect retinal nerve fiber layer (RNFL) thickness measurement obtained with a spectral domain optical coherence tomography.
Twenty-five normal volunteers and 29 glaucoma subjects were recruited for this cross-sectional study. One eye was selected at random from each subject for circumpapillary RNFL scan by the Spectralis OCT (Heidelberg Engineering, Heidelberg, GmbH, Dossenheim, Germany). Three sets of OCT image series comprising 2, 8, and 16 consecutive B-scans were obtained in the same visit (Figure 1). The technologies of eye tracking and image registration ensured the same retinal location was scanned. The global and sectoral (superonasal, nasal, inferonasal, inferotemporal, temporal, and superotemporal) RNFL thicknesses were compared with repeated measures ANOVA among the image series with different numbers of B-scans.
The respective global RNFL thickness after 2, 8, and 16 multiple B-scan imaging were 105.84 ± 13.42 µm, 106.92 ± 13.62 µm, and 106.12 ± 12.98 µm for the normal group; and 70.17 ± 21.01 µm, 70.24 ± 20.73 µm, and 70.62 ± 21.56 µm for the glaucoma group. There were no significant differences in RNFL measurement among the groups with different numbers of B-scan (p = 0.116 and 0.503, respectively). Significant differences in RNFL thickness (all below 2µm), however, were detected in the nasal sector for the normal group and in the inferonasal sector for the glaucoma group (p = 0.044 and 0.038, respectively) (Table 1).
The number of images used in multiple B-scan averaging may not influence global RNFL thickness although caution should be exercised in interpretation of nasal RNFL measurement in diagnosing and following patients with glaucoma.
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