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22 December 1997 Laser thermokeratoplasty: analysis of in-vitro results and refractive changes achieved in a first clinical study
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Laser thermokeratoplasty (LTK) is a minimally invasive method to correct hyperopia and astigmatism. A cw mid-IR laser diode emitting at wavelengths around 1.86 micrometers was used to perform LTK on a first clinical trial. The coagulations were applied to the cornea by means of a specially designed focusing handpiece which was introduced into a corneal application mask fixed by a suction ring. Coagulation patterns consisting of 8 spots per ring were performed with a laser power between 100 - 150 mW and an irradiation time of 10 seconds both on single and on double rings. Significant refractive changes up to 19 D could initially be achieved followed by a strong regression within the first month. Three months post LTK, refractive changes achieved with the single and double ring have stabilized, yielding 1.2 and 1.8 D on the average, respectively. The method reveals only little adverse effects limited to the first days post-op. Force measurements were performed on corneal stripes, which were submerged for 10 s into an oil bath of constant temperature in order to investigate the absolute temperatures required for corneal collagen contraction. Only temperatures exceeding 90 degree(s)C induced a significant force. Analyzing the clinically used LTK parameters by temperature calculations revealed that only a small part of the heated stromal volume experienced sufficient high temperatures to induce significant collagen shrinkage.
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Ralf Brinkmann, Gerd Geerling, Juergen Kampmeier, Norbert Koop, Benno Radt, and Reginald Birngruber "Laser thermokeratoplasty: analysis of in-vitro results and refractive changes achieved in a first clinical study", Proc. SPIE 3192, Medical Applications of Lasers in Dermatology, Ophthalmology, Dentistry, and Endoscopy, (22 December 1997);

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