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Elaine Thung, Shane Knipping, Joseph Caprioli, Kouros Nouri-Mahdavi; Global and Regional Intrasession Test-Retest Variability of Macular Thickness Measurements with Spectral-domain Optical Coherence Tomography with and without Tracking. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5533.
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© ARVO (1962-2015); The Authors (2016-present)
To compare regional and global intrasession test-retest variability of macular thickness (MT) measurements with Spectral-domain Optical Coherence Tomography (SD-OCT) with and without tracking in a group of glaucoma and normal eyes.
Ninety-nine eyes of 56 patients (38 normal eyes, 10 glaucoma suspect eyes, and 51 glaucoma eyes) that underwent three consecutive macular scans in the same session (Glaucoma Posterior Pole Algorithm, 8x8 cell matrix of macular thickness measurements centered on fovea, Spectralis SD-OCT) with and without activation of the tracking system were included in this study. Variances for global thickness measurements and square root of pooled sum of variances in individual cells and 2x2 or 4x4 grids were compared with and without tracking. The effect of baseline macular thickness on the magnitude of variability was also explored.
Seventy-five eyes were imaged with macular tracking (MTr group) and 24 eyes were imaged without macular tracking (NMTr group). The average global MT was 273.2 μm and 271.7 μm in the MTr and NMTr groups, respectively (p=0.467). The average MT measurements were 275.6 μm for the individual cells, 275.6 μm for the 2x2 grid, and 273.2 μm for the 4x4 grid for the MTr group vs. 274.2 μm for the individual cells, 274.4 μm for the 2x2 grid, and 274.2 μm for the 4x4 grids for the NMTr group (p>0.05 for all). The average square root of the pooled variances was 30.2 μm for the individual cell, 28.3 μm for the 2x2 grid, 17.1 μm for the 4x4 grids, and 1.4 μm for the global measurement for the MTr group. The corresponding values for the NMTr group were 33.9 μm for the individual cells, 31.1 μm for the 2x2 grids, 17.4 μm for the 4x4 grids, and 3.8 μm for the 8x8 grids (p=0.04 for individual cells, p=0.055 for 2x2 grids, p=0.91 for the 4x4 grids, and p=0.003 for global variance; Levene's robust test statistic for equality of variances). Intrasession variability increased with increasing macular thickness (p<0.001).
The average variance of macular thickness test-retest measurements decreased with increasing grid size within the posterior pole. Using macular tracking system significantly improved intrasession test-retest variability for macular SD-OCT imaging. Intrasession variability correlated positively with macular thickness measurements.
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