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17 May 1996 Depth-adjusted thermal keratoplasty using a cw diode laser and a new focusing handpiece
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Thermal keratoplasty is currently performed with a Ho:YAG laser at 2.1 micrometer wavelength. Long term stability critically depends upon the coagulation depth of each cone and thus upon emission wavelength, absorption and focusation, all contributing to controlled collagen shrinkage in order to induce central corneal steepening. Cw properties meet coagulation requirements more effectively by avoiding tissue cooling by thermal diffusion as well as peak temperatures of pulsed lasers. Both of these factors interfere negatively with collagen shrinkage. Therefore, a cw diode laser has been developed, emitting at 1.9 micrometer (absorption in water, comparable to Ho:YAG) with a maximal energy output of 400 mJ. For corneal application, the laser was coupled into a depth adjustable handpiece which allows the user to react to corneal thickness (maximal in the 6 h position) and its interindividual variation, covering a depth range between 350 micrometer and 800 micrometers. The histology of 10 porcine and 6 human cadaver corneas coagulated in vitro, revealed a similar spot geometry compared to conventional Ho:YAG radiation if the same total energy is applied. Higher corrections and better long term stability appear to be clinically achievable.
© (1996) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Benedikt J. Jean M.D., Thomas Bende, Theo Oltrup, Michael Matallana, and Rudolf Walker "Depth-adjusted thermal keratoplasty using a cw diode laser and a new focusing handpiece", Proc. SPIE 2673, Ophthalmic Technologies VI, (17 May 1996);

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