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,

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.

Purpose: To study parameters for ocular femtosecond laser surgery in terms of process efficiency and safety aspects using ultraviolet (UV) femtosecond laser pulses. Methods: Studies on corneal surgery and flap processing on enucleated porcine eyes were performed using a newly developed ytterbium-doped gain media laser source. Ultraviolet femtosecond laser pulses centered at a wavelength of 345 nm and working at a repetition rate of 100 kHz were generated by the third harmonics of the 1035-nm fundamental wavelength. Results: Flaps with a diameter of 6 mm and a thickness of 100 µm were created in less than 2 minutes with low energy pulses. Transmissions and spectral measurements were performed during flap processing. Less than 2% UV radiation reaches the retina during corneal flap processing. A detectable transmittance towards the retina of visible light centered on 440 nm was found for UV pulses. Conclusions: Ultraviolet corneal refractive surgery is a novel procedure and has the potential to be an alternative to infrared refractive surgery considering safety aspects. [ J Refract Surg . 2009;25:383–389.]

We report on the influence of femtosecond laser pulses at different wavelengths (1035, 517, and 345nm) on chinese hamster ovary cells exposed to intense radiation. The aim of the study was to determine the mean power thresholds from which the cells were influenced by the laser radiation up to irreversible cell damage. An influence of the wavelength has been shown. The damage threshold is lower in the ultraviolet (UV) than in the infrared (IR) by a factor of 5–6. At the green wavelength the threshold value was higher due to the low absorption (i.e., a relatively high transmission). The range between the lowest power where a loss of viability could be observed (25μW) and the mean power for direct cell damage (45μW) is 20μW in the UV. The corresponding range in the IR is between 75 and 240μW and thus about 165μW broad: In the case of UV irradiation, the cells seem to be unaffected close to the ablation or damage threshold at low energy pulses.

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