title: Ocular aberrations measured by the Fourier-based WaveScan and Zernike-based LADARWave Hartmann-Shack aberrometers.
abstract: To evaluate agreements in lower and higher order aberration measurements by two Hartmann-Shack wavefront-sensing devices.
  
  
  
  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.
  
  
  
  Mean absolute defocus for WaveScan and LADARWave was 2.82 +/- 2.69 and 2.93 +/- 3.24 root-mean-square (RMS) microm, whereas astigmatism was 0.81 +/- 0.49 and 0.87 +/- 0.57 microm, 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 quadra-foil [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 microm, and only 44% of eyes having less than +/-0.10 RMS microm of difference. The mean total higher order aberration absolute difference was 0.14 +/- 0.14 microm, with only 50% of eyes within +/-0.1 RMS of agreement. Vector analysis revealed appreciable discrepancies in third- and fourth-order directional Zemike components, while showing similar values for fifth-order components. Intra-class correlation coefficient values for both aberrometers over different aberration orders showed excellent repeatability.
  
  
  
  The WaveScan and LADARWave share similar lower order aberration measurements, but display significantly different higher order aberration values.
authors.affiliation: Department of Ophthalmology, UT Southwestern Medical Center, Dallas, Texas 75390-9057, USA.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Knapp
authors.forename: Shady T
authors.initials: ST
authors.lastname: Awwad
authors.forename: Claudine
authors.initials: C
authors.lastname: Ghali
authors.forename: James P
authors.initials: JP
authors.lastname: McCulley
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000175:diagnosis; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D008297:Male; D008875:Middle Aged; D012030:Refractive Errors / Q000175:diagnosis*; D015203:Reproducibility of Results; D014792:Visual Acuity