Medical applications of excimer lasers

Abstract

Excimer laser radiation, especially at the wavelength of 193nm, is well suitable for processing biological tissue. Its absorption length is below 0.25μm and due to the short interaction time of only several nanoseconds, the collateral thermal damage of ArF-laser-ablated tissue is limited to less than 100nm with a uniformly appearing surface [1, 2]. Micro surgical interventions like refractive surgery of the eye take advantage of this high quality standard. However, due to the poor transmission of 193nm radiation through optical fibers, endoscopical operations inside the human body are impossible today. 248nm radiation of KrF lasers shows better transmission, but this wavelength is banned for medical application due to its high mutagenic risk [3, 4]. At 308nm the mutagenic risk is negligible and fiber transmission is satisfactory. Though the absorbance has decreased by more than one order of magnitude at 308nm, surgical interventions which allow a thermal damage of some 10μm are possible applications. The main clinical application for 308nm radiation is laser angioplasty where occluded vessels are opened by means of photoablation via an optical fiber. Another promising attempt of 308nm photoablation is an ophthalmological application: The reduction of the intra-ocular pressure on glaucoma surgery. © 2005 Springer-Verlag Berlin Heidelberg.