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M. Shirayama, L. Wang, D. D. Koch; Repeatability of Corneal Powers and Wavefront Aberrations Measured with the Galilei Dual Scheimpflug Analyzer. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5100.
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To evaluate the repeatability of the corneal powers, corneal wavefront aberrations, pachymetry and anterior chamber depth (ACD) measured with the Galilei (Version 3.0).
Prospectively, three consecutive measurements were performed in one eye of 20 subjects by one observer, with subjects sitting back and re-focusing before each measurement. Four categories of parameters were evaluated: 1) corneal powers: Simulated K (SimK, 1-4 mm zone), posterior corneal power (Kpost, 1-4 mm), and central, paracentral and peripheral average total corneal powers (TCP, 0-4 mm, 4-7 mm, and 7-8 mm, respectively); 2) total corneal higher-order wavefront aberrations (HOAs, 3rd-6th order) for 6-mm pupil; 3) central, paracentral and peripheral average pachymetry, and 4) ACD. To assess the repeatability, the standard deviation (SD) of the repeated measurements, coefficient of variation (CV, ratio of SD and mean), and intraclass correlation coefficient (ICC) values were calculated.
For corneal powers, the SD values were 0.06 D and 0.02 D for SimK and Kpost, and 0.07 D, 0.05 D and 0.15 D for central, paracentral and peripheral TCP, respectively; the CV ranged from 0.10% to 0.35%, and ICC ranged from 0.996 to 0.999 (all P<0.001). For total corneal wavefront aberrations, the SD values ranged from 0.06 µm to 0.10 µm for 3rd-order Zernike coefficients, and 0.02 µm to 0.08 µm for 4th-order Zernike coefficients, and 0.02 µm, 0.02 µm and 0.08 µm for 5th-, and 6th- order root-mean-square (RMS) and HOAs RMS, respectively; the CV values ranged from 14% to 29%, and ICC ranged from 0.787 to 0.878 for 3rd-, 4th-, 5th-, and 6th-order RMS and HOAs RMS (all P<0.001). For central, paracentral and peripheral pachymetry, respectively, the SD values were 1.39 µm, 1.74 µm, and 2.58 µm; the CV values ranged from 0.25% to 0.38%; and ICC values were 0.999 (P<0.001). For the ACD, the SD was 0.02 mm, CV was 0.69%, and ICC was 0.996 (P<0.001).
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