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GH Pettit, JA Campin, KK Liedel, GP Gray; Impact Of Wavefront Aberrations On Visual Performance . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4157.
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Purpose: Wavefront sensing is rapidly being incorporated into refractive laser surgery. In using this technology to evaluate outcomes and optimize ablation profiles it is important to know the true impact of the measured aberrations on visual function. Methods: An Alcon Hartmann-Shack wavefront sensing device was used to measure visual aberrations for a population of normal patients undergoing LASIK surgery (N ≷ 300). This instrument allows accurate registration of the wavefront data to the geometry of the eye, so that measurements made at different sessions can be precisely correlated to each other. Wavefront data were analyzed against clinical parameters (e.g., high and low contrast VA, etc.) for pre-operative examinations and for exams three months after surgery. Regression analysis was used to identify trends between individual Zernike coefficients and clinical measures. Results: Predictably, pre-operative uncorrected visual acuity was most highly correlated with the amplitude of the defocus error under either high or low contrast conditions (correlation coefficient = -0.59 and –0.35 respectively). BCVA was most highly correlated with oblique astigmatism amplitude under either contrast condition (correlations of -0.10 and –0.22). Post-operative high contrast UCVA was most strongly correlated with the spherical aberration term (+0.27), while low contrast UCVA was again best correlated with defocus (-0.32). In addition, post-operatively there was a small but consistent negative correlation between secondary astigmatism and most of the clinical parameters. Further, the slope dependencies on these aberrations were typically larger than those for other parameters. Computer simulation of visual function in the presence of various aberrations also showed a marked negative effect on VA by secondary astigmatism. Of the two secondary astigmatic terms, the oblique aberration was more highly correlated to the clinical data, and with larger negative slopes. Conclusion: Studying the relationship between visual performance and Zernike wavefront aberrations does reveal modest but consistent trends. Oblique astigmatism terms, both primary and secondary, appears to be notably debilitating to vision.
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