In vitro measurements of cytotoxic effects of 193 nm and 213 nm laser pulses at subablative fluences.
OBJECTIVE
The frequency-quintupled q-switched Nd:YAG laser is being studied as an alternative to the ArF excimer laser for photorefractive procedures. The present report describes two experiments comparing biologic effects of these laser devices.


METHODS
Bovine corneas were irradiated with subablative laser pulses in liquid nitrogen and analyzed by electron paramagnetic resonance spectroscopy to assess free radical production. Aqueous bacterial suspensions were irradiated with low-intensity laser pulses and assayed for cell survival.


RESULTS
Electron paramagnetic resonance spectra were very similar in both amplitude and shape for exposure at the two wavelengths. Bacterial survival was markedly less for 213 nm irradiation than 193 nm exposure and displayed a different dependence on cumulative exposure.


CONCLUSIONS
Free radical production by 213 nm laser exposure is quite comparable to that seen previously for 193 nm irradiation. However, cell lethality appears to be significantly greater at the longer ultraviolet wavelength. This difference may contribute to complications observed after corneal photoablation with the 213 nm device.
Ediger
M N
MN
Center for Devices & Radiological Health, Food and Drug Administration, Rockville, Maryland 20857, USA.
Pettit
G H
GH
Matchette
L S
LS
D000818:Animals; D002417:Cattle; D002470:Cell Survival / Q000528:radiation effects; D003315:Cornea / Q000378:metabolism / Q000528:radiation effects / Q000601:surgery*; D004578:Electron Spin Resonance Spectroscopy; D004926:Escherichia coli / Q000528:radiation effects; D005609:Free Radicals; D066298:In Vitro Techniques; D054018:Lasers, Excimer; D018903:Photorefractive Keratectomy / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods
D005609:Free Radicals