title: Evaluation of refractive error measurements of the Wavescan Wavefront system and the Tracey Wavefront aberrometer.
abstract: OBJECTIVE
  To evaluate the accuracy and repeatability of the WaveScan WavePrint system and the Tracey wavefront aberrometer in measuring refractive errors in phakic eyes.
  
  
  METHODS
  Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA.
  
  
  METHODS
  Using subjective manifest refraction (MR) as the standard, the spherical equivalent (SE), sphere, and cylinder were compared to values measured by WaveScan and Tracey devices in virgin eyes and eyes that had had corneal refractive surgery. Astigmatism was evaluated using vector analysis. The accuracy of the WaveScan and Tracey devices was assessed by 95% limits of agreement (95% LA), and repeatability was analyzed by 2 standard deviations (SDs) and intraclass correlation coefficients (ICCs).
  
  
  RESULTS
  The mean differences in SE, sphere, and cylinder between MR and WaveScan were -0.26 diopter (D), -0.12 D, and -0.28 D, respectively, and between MR and Tracey, -0.21 D, -0.01 D, and -0.40 D, respectively. The 95% LA for SE, sphere, and cylinder were -1.09 to 0.57 D, -1.14 to 0.89 D, and -0.95 to 0.40 D, respectively, for WaveScan and -1.37 to 0.95 D, -1.27 to 1.26 D, and -1.16 to 0.35 D, respectively, for Tracey. Vector analysis revealed mean differences of -0.47 +0.07 x 9 degrees between MR and WaveScan and of -0.53 +0.27 x 12 between MR and Tracey. The 2 SDs for SE, sphere, and cylinder were 0.26 D, 0.29 D, and 0.16 D, respectively, for WaveScan and 0.31 D, 0.36 D, and 0.33 D, respectively, for Tracey. The ICCs for SE, sphere, and cylinder were 0.993, 0.992, and 0.902, respectively, for WaveScan and 0.994, 0.992, and 0.764, respectively, for Tracey. The Tracey device measured all eyes evaluated; the WaveScan could not measure 14% of normal eyes and 50% of post laser in situ keratomileusis eyes.
  
  
  CONCLUSIONS
  Using MR as the standard, refractive errors measured by the WaveScan and Tracey devices were reliable and reproducible. However, the Tracey device was more robust in its ability to obtain measurements in normal and postoperative eyes.
authors.affiliation: Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, 6565 Fannin, Houston, TX 77030, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.forename: Nan
authors.initials: N
authors.lastname: Wang
authors.forename: Douglas D
authors.initials: DD
authors.lastname: Koch
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000175:diagnosis; D003315:Cornea / Q000473:pathology; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation*; D006801:Humans; D008875:Middle Aged; D012029:Refraction, Ocular; D012030:Refractive Errors / Q000175:diagnosis*; D015203:Reproducibility of Results