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H. Specht, H.E. Voelcker, F.E. Kruse; Scanning Electron Microscopic Determination of Ablation Patterns and Laser Parameters for Non-Mechanical Trephination With a New Fiber Optic Device for the 308 NM Excimer Laser . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4697.
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Purpose: Compared to conventional methods a newly developed non-mechanical Excimer laser trephine with a new fiber optic unit offers distinct advantages for penetrating keratoplasty. Here we describe the optimized parameters of application for this simple trephine which can be used in conjunction with small, mobile, laser units. Methods: A motor driven trephine was developed which can be centered by use of a suction ring. It is used in conjunction with a fiber that is connected to a small, mobile, commercially available 308nm Excimer laser. In a pre clinical study freshly enucleated pig an human eyes were used. The following parameters were examined: Power density (10mJ/mm² – 40mJ/mm²), repetition rate (10 Hz – 100 Hz), fiber diameter (100µm, 200µm, 300µm), overlap (0%, 25%, 50%, 75%). Conventional histology and Scanning Electron Microscopy (SEM) of cuts with the laser trephine were performed. Results: The laser trephine is easy to use and allows to precisely cut both porcine and human corneas. The SEM showed smooth cutting edges and the histology showed a thermal damage of less than 10µm. The minimum time needed for the entire cut was with approximately 1.5 min at 300µm diameter of the ablation pattern without overlap and a repetition rate of 100 Hz. The power density was about 20mJ/mm². Conclusions: Depending on the overlap of the laser spots and power densities the accuracy of the cut and the time necessary to complete perforation can be modified. Our new laser trephine system offers advantages over the current method of Excimer laser trephination and its practicability should allow widespread clinical use.
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