Laser thermokeratoplasty: analysis of in-vitro results and refractive changes achieved in a first clinical study

Ralf Brinkmann*, Gerd Geerling, Jürgen Kampmeier, Norbert Koop, Benno Radt, Reginald Birngruber

*Corresponding author for this work


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 μm 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°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.

Original languageEnglish
JournalProceedings of SPIE - The International Society for Optical Engineering
Pages (from-to)180-186
Number of pages7
Publication statusPublished - 22.12.1997
EventProceedings of Medical Applications of Lasers in Dermatology, Ophthalmology, Dentistry and Endoscopy 1997 - San Remo, Italy
Duration: 04.09.199707.09.1997
Conference number: 59693

Research Areas and Centers

  • Academic Focus: Biomedical Engineering


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