Dipl Ing (FH), Christian Wüllner, Dipl Ing (FH), Joachim Löffler, Dipl Ing (FH)Purpose: To describe a method for calculating wavefront-optimized ablation profiles to precompensate for the spherical aberration and higher-order astigmatism induced by myopic, hyperopic, and astigmatic corneal laser corrections. Setting:Methods: The basic ablation profile for myopic, hyperopic, and astigmatic correction is derived from the 2nd-order Zernike representation of wavefront aberrations. Including 4th-order spherical aberration and higher-order astigmatism in the theoretical calculation of the ablation profile allows precompensation for the expected amount of higher-order aberrations (HOAs). The shapes of wavefront-optimized ablation profiles are compared with the shapes of "classic" ablation profiles for myopic and astigmatic corrections. Results:The introduction of precompensating spherical aberration and higherorder astigmatism leads to a more aspheric ablation profile with a significant increase in ablation depth (up to 35%) in the midperiphery of the optical zone. The central ablation depth remains unchanged in the myopic correction but increases by 3% in cylinder correction.Conclusions: Wavefront-optimized ablation profiles provide a simple method to precompensate for the expected 4th-order spherical aberration and higher-order astigmatism in the average eye. Further clinical studies must be performed to prove the theoretical results; demonstrate the reduction in HOAs; and predict safety, predictability, and stability of wavefront-optimized ablation profiles. J Cataract Refract Surg 2004; 30:775-785  2004 ASCRS and ESCRSthat the best-corrected image quality degrades after cor-M odern corneal laser surgery aims for customizaneal refractive surgery. Reasons for the observed increase tion to improve the optical and visual outcomes in higher-order (wavefront aberration) optical aberraof the refractive procedure. One major weak point in tions after corneal laser surgery are manifold. "classic" photorefractive treatments for myopia, hyperScanning algorithms and spot size. Changes in the opia, and astigmatism is the postoperatively observed ablation depth for each laser pulse when moving the increase in higher-order aberrations (HOAs). Studies laser beam from the corneal apex toward the limbus based on corneal aberrations, 1-12 wavefront aberrachanges the angle of incident light, resulting in signifitions, 13-19 and visual performances 2,3,5,18,20,21 demonstrate cant undercorrection in the periphery and consequent generation of spherical aberrations. 22-25 Besides this, mathematical algorithms for precise overlapping of single laser spots 26,27 have been described. The use of spots Reprint requests to Michael Mrochen, PhD, Swiss Federal Institute of of 0.5 to 2.0 mm might not be sufficient to completely Technology and University of Zürich, Institute of Biomedical Engicorrect optical aberrations or might induce other types neering,

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High-repetition-rate excimer laser systems require spot sequences with optimized temporal and spatial spot distribution to minimize the increase in ocular surface temperature. An ocular surface temperature increase will always occur depending on the amount of refractive correction, the type of ablation profile, the radiant exposure, and the repetition rate of the laser system.

The temporal and spatial distribution of the laser spots (scan sequence) during a corneal laser procedure affected the surface quality and maximum ablation depth of the ablation profile. Corneal laser surgery could theoretically benefit from smaller spot sizes and higher repetition rates. The temporal and spatial spot distributions are relevant to achieving these aims.

The WaveLight FS200 femtosecond laser provides a high reproducibility for cutting three-dimensional tissue structures. The IOP increase is comparable to other microkeratomes and femtosecond lasers. The minimized opaque bubble layers allow the surgeon to perform an excimer laser treatment immediately after FS200 flap creation.