[193 nm Excimer laser photoablation of the cornea. Spectrum and transmission behavior of secondary irradiation].
In order to estimate the photomutagenic and phototoxic potential involved we analyzed the spectrum and intensity of secondary radiation induced with a 193 nm excimer laser in photoablation of corneal tissue. The spectrum of secondary radiation was analyzed by an optical multichannel analyzer. A pyroelectrical detector was used to evaluate the energy of the secondary radiation. We found the secondary radiation to be in the range of ultraviolet to infrared. The spectrum has a relatively high quantity (20%) of radiation between 240 and 280 nm. The intensity of the secondary radiation depends on the energy fluence of the primary laser pulse and can reach a quantum yield of up to 10(-3) (at 800 mJ/cm2). At a fluence of 230 mJ/cm2 (193 nm), the secondary radiation in the range of 240-280 nm is approximately 5 microJ/cm2. Radiation below 300 nm was not transmitted through the cornea. Since the high genetic activity of UV radiation in the range from 240-280 nm is well known, evaluation of the potential mutagenicity of 193 nm excimer laser radiation should take into consideration the presence of secondary radiation in this problematic spectral range. However, there is no incidence known for specific UV-induced corneal cancers, which supports the argument that the potential mutgenic risk of clinical excimer laser application can be considered to be low. Because of the full corneal absorption of radiation below 300 nm, there is no risk known for pigmented intraocular structures.
Lubatschowski
H
H
Institut für Angewandte Physik, Universität Bonn.
Kermani
O
O
D000818:Animals; D003315:Cornea / Q000473:pathology / Q000528:radiation effects / Q000601:surgery*; D008028:Light Coagulation / Q000009:adverse effects / Q000295:instrumentation*; D011833:Radiation Injuries, Experimental / Q000473:pathology; D012542:Scattering, Radiation; D013552:Swine
193 nm Excimer-laserphotoablation der Hornhaut. Spektrum und Transmissionsverhalten von Sekundärstrahlung.