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RESEARCH PRODUCT

Comparison of higher order aberrations measured by NIDEK OPD-Scan dynamic skiascopy and Zeiss WASCA Hartmann-Shack aberrometers.

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<h4>PURPOSE</h4><p>To compare the measurement of wavefront aberrations in non-cyclopleged human eyes with Hartmann-Shack and dynamic skiascopy wavefront analyzers.</p> <h4>METHODS</h4><p>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.</p> <h4>RESULTS</h4><p>The coefficient of repeatability for the WASCA ranged from 0.008 to 0.022 µm. Data distribution was normal for all Zernike coefficients measured with WASCA, but only for Z<sub><img src="http://www.journalofrefractivesurgery.com/images/jrs/248/_13.gif" alt="" width="9" height="16" border="0"></sub>, Z<sub><img src="http://www.journalofrefractivesurgery.com/images/jrs/248/13.gif" alt="" width="9" height="16" border="0"></sub>, and Z<sub><img src="http://www.journalofrefractivesurgery.com/images/jrs/248/04.gif" alt="" width="9" height="16" border="0"></sub> measured with the OPD-Scan. Mean differences between instruments in coefficients Z<sub><img src="http://www.journalofrefractivesurgery.com/images/jrs/248/_33.gif" alt="" width="9" height="16" border="0"></sub>, Z<sub><img src="http://www.journalofrefractivesurgery.com/images/jrs/248/13.gif" alt="" width="9" height="16" border="0"></sub>, Z<sub><img src="http://www.journalofrefractivesurgery.com/images/jrs/248/33.gif" alt="" width="9" height="16" border="0"></sub>, Z<sub><img src="http://www.journalofrefractivesurgery.com/images/jrs/248/04.gif" alt="" width="9" height="16" border="0"></sub>, and Z<sub><img src="http://www.journalofrefractivesurgery.com/images/jrs/248/24.gif" alt="" width="9" height="16" border="0"></sub> 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 µm, respectively, <i>P</i><.05 in all cases). Correlation coefficients were significant only for higher order RMS (Spearman’s rho=0.777; <i>P</i>>.001). </p> <h4>CONCLUSIONS</h4><p>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. [<cite>J Refract Surg.</cite> 2008;24:790-796.]</p> <h4>ABOUT THE AUTHORS</h4> <p>From the Department of Optics, University of Valencia, Valencia, Spain (Cerviño, Montés-Micó); School of Life and Health Sciences, Aston University, Birmingham, United Kingdom (Cervino, Hosking); the Department of Optometry and Visual Sciences, City University, London, United Kingdom (Hosking); and the Department of Ophthalmology, University of Melbourne, Melbourne, Australia (Hosking).</p> <p>The authors have no proprietary or financial interest in the materials presented herein.</p> <p>Correspondence: Alejandro Cerviño, OD, PhD, MCOptom, Dept of Optics, University of Valencia, C/Dr Moliner, 50, 46100 (Burjassot), Valencia, Spain. Tel: 34 963544343; Fax: 34 963544715; E-mail: <a href="mailto:alejandro.cervino@uv.es">alejandro.cervino@uv.es</a></p> <p>Received: April 29, 2007</p> <p>Accepted: November 7, 2007</p> <p><b>Posted online: March 15, 2008</b></p>