Absorption of 308-nm excimer laser radiation by balanced salt solution, sodium hyaluronate, and human cadaver eyes
R. H. Keates, R. T. Bloom, R. T. Schneider, Q. Ren, J. Sohl and J. J. Viscardi
Department of Ophthalmology, University of California, Irvine 92717.
Absorption of the excimer laser radiations of 193-nm argon fluorine and
308-nm xenon chloride in balanced salt solution, sodium hyaluronate, and
human cadaver eyes was measured. The absorption of these materials as
considerably different for the two wavelengths; we found that 308-nm light
experienced much less absorption than the 193-nm light. The extinction
coefficient (k) for 308 nm was k = 0.19/cm for balanced salt solution and k
= 0.22/cm for sodium hyaluronate. In contrast to this, the extinction
coefficient for 193 nm was k = 140/cm for balanced salt solution and k =
540/cm for sodium hyaluronate. Two 1-day-old human phakic cadaver eyes
showed complete absorption with both wavelengths. Using aphakic eyes,
incomplete absorption was noted at the posterior pole with 308 nm and
complete absorption was noted with 193 nm. The extinction in the anterior
part of aphakic eyes (the first 6 mm) was 4.2/cm for 308 nm, meaning that
the intensity of the light is reduced by a factor of 10 after traveling the
first 5.5 mm. However, we observed that the material in the eye fluoresces,
meaning the 308 nm is transformed into other (longer) wavelengths that
travel through the total eye with minimal absorption. Conclusions drawn
from this experiment are that the use of the 308-nm wavelength may have
undesirable side effects, while the use of the 193-nm wavelength should be
consistent with ophthalmic use on both the cornea and the lens.
