Abstract:
PURPOSE: To evaluate agreements in lower and higher order aberration measurements by two Hartmann-Shack wavefront-sensing devices. METHODS: Using the VISX WaveScan and Alcon LADARWave aberrometers, ocular aberrations at a fixed optical zone of 6 mm were measured on 36 eyes of 18 patients. A tunable light intensity source was used to control pupil size, which was checked using infrared pupillometry. Repeatability of measurements was evaluated using the intra-class correlation coefficient with 3 consecutive measurements on each aberrometer. RESULTS: Mean absolute defocus for WaveScan and LADARWave was 2.82±2.69 and 2.93±3.24 rootmean-square (RMS) μm, whereas astigmatism was 0.81±0.49 and 0.87±0.57 μm, respectively. Pearson correlation coefficients between the two aberrometers were 0.908 and 0.870 for defocus and astigmatism, respectively, whereas higher order aberration correlation was less tight (Pearson correlation coefficient=0.596 for coma, 0.746 for trefoil, 0.836 for spherical aberration, 0.637 for secondary astigmatism, and 0.963 for quadrafoil [P.001 for all]). The LADARWave had a tendency to display more spherical aberration than the WaveScan, especially at high aberration values, with mean absolute difference in measurement of 0.12±0.08 μm, and only 44percent of eyes having less than ±0.10 RMS pm of difference. The mean total higher order aberration absolute difference was 0.14±0.14 μm, with only 50percent of eyes within ±0.1 RMS of agreement. Vector analysis revealed appreciable discrepancies in third- and fourth-order directional Zernike components, while showing similar values for fifth-order components. Intra-class correlation coefficient values for both aberrometers over different aberration orders showed excellent repeatability. CONCLUSIONS: The WaveScan and LADARWave share similar lower order aberration measurements, but display significantly different higher order aberration values.