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Geoffrey T. Dair, Wayne S. Pelouch, Paul P. van Saarloos, Darren J. Lloyd, Simone M. Paz Linares, Fred Reinholz; Investigation of Corneal Ablation Efficiency Using Ultraviolet 213-nm Solid State Laser Pulses. Invest. Ophthalmol. Vis. Sci. 1999;40(11):2752-2756.
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purpose. To determine the threshold and efficiency of corneal ablation for
various values of laser fluence at the ultraviolet wavelength of 213
methods. A commercial Q-switched Nd:YAG laser was used to produce the fifth
harmonic wavelength of 213 nm. Ablation trials were carried out on
porcine corneas. Slit ablations of dimensions 0.5 × 2.5 mm were
performed using seven values of laser fluence to obtain the most
efficient fluence for ablation. The morphology of each ablation was
obtained using a computer-automated confocal profiling system. These
profiles were then analyzed to determine the ablation depth for the
range of fluence values used.
results. A fluence in the region of 200 mJ/cm2 was found to be the
most efficient for ablation. The efficiency in this region was
approximately 0.35 mm3/J, and the ablation rate was found
to be 0.6 μm/pulse. The ablation threshold was found to occur at a
fluence of 50 mJ/cm2. In the region of highest efficiency,
the peak varied slightly in the fluence range between 150 and 250
conclusions. This study confirms that the corneal ablation properties at 213 nm are
comparable with those at the 193-nm excimer laser wavelength. Increased
pulse energy was obtained for the fifth harmonic of Nd:YAG lasers at
213 nm through the use of new nonlinear optical crystals to perform the
frequency conversion. A solid state laser is feasible to replace the
excimer gas laser for performing refractive surgery procedures. For the
first time, the increased energy at 213 nm allows large-beam ablations
to be performed at this wavelength.
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