Comparison of Higher Order Aberrations Measured by NIDEK OPD-Scan Dynamic Skiascopy and Zeiss WASCA Hartmann-Shack Aberrometers

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To compare the measurement of wavefront aberrations in non-cyclopleged human eyes with Hartmann-Shack and dynamic skiascopy wavefront analyzers. Eighty eyes of 40 healthy young adults (19 men, 21 women; mean age 20.8 +/- 2.5 years) with refractive errors ranging from +1.50 to -9.75 diopters (D) sphere and up to 1.75 D cylinder (mean spherical equivalent refraction -2.12 +/- 2.69 D) were examined with the Zeiss/Meditec WASCA and NIDEK OPD-Scan wavefront analyzers and with the Nippon SRW5000 binocular, open-field autorefractor without the instillation of antimuscarinic agents. Three measurements were taken with each system, in randomized sequence. To avoid differences due to instrument myopia, eyes were excluded if mean spherical equivalent refraction with any of the analyzers exceeded those obtained with the SRW5000 by more than 1.00 D; 13 eyes were excluded. Coefficient of repeatability was determined for the WASCA as the confidence interval (CI) for the differences between the repeated measures. Paired t tests with Bonferroni adjustment for multiple comparisons, correlation analysis, and Bland-Altman plots of difference versus mean were performed. The coefficient of repeatability for the WASCA ranged from 0.008 to 0.022 microm. Data distribution was normal for all Zernike coefficients measured with WASCA, but only for Z(3)(-1), Z(3)(1), and Z(4)(0) measured with the OPD-Scan. Mean differences between instruments in coefficients Z(3)(-3), Z(3)(1), Z(3)(3), Z(4)(0), and Z(4)(2) and higher order root-mean-square (RMS) reached statistical significance (mean difference +/- CI: -0.054 +/- 0.021, -0.056 +/- 0.022, and 0.030 +/- 0.016 microm, respectively, P < .05 in all cases). Correlation coefficients were significant only for higher order RMS (Spearman's rho = 0.777; P > .001). Although agreement is shown for higher order RMS, aberration values obtained with dynamic skiascopy and Hartmann-Shack systems on non-cyclopleged human eyes are not well correlated with each other, and are therefore not interchangeable.