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Toxicological Study of Laser-Induced Pyrolysis
Products in Cataract Surgery Specht H, Auffarth
GU, Burk ROW, Voelcker HE
Introduction Phacoemulsification is the standard
in cataract surgery. Ultrasonic
phacoemulsification is highly effective and today
standardizied. Concerns exist about the potential
risks of ultrasonic energy delivered by the
phacoemulsification tip on such nontarget ocular
structures a s the corneal endothelium 2. Laser
assisted cataractous lens removal has been
investigated because of ergonomic considerations
and the desire to minimize surgical invasiveness
5. Several laser technologies from the
wavelength of UV to IR have been investigated
there for. Different methods of nucleus cracking
are capable mostly used is the ErYAG laser in
directly contact mode 4. In contrast to a
standard phaco procedure only small openings
within the corneal tissue are aimed for. The
purpose of this in vitro study is to evaluate the
feasibility of toxicological risks 1 of the
pyrolysis products 3 created by ErYAG laser
Treatment of lens fragment (assembled from
clinical cataract patients). Purpose To
estimate the possibility of toxically pyrolysis
products after laser treated cataractous nucleus
under surgical conditions. Materials and
Methods Photoablation Used was a ErYAG laser
(Fig.4 InPro Hamburg, Germany Type CUT 2940) in
the normal spiking mode. The ErYAG emits a
radiation of 2.94 µm with a tuneable pulse
lengths lt 600 µs and a repetition rate lt 10 Hz up
to a maximal averaged power of 10 W. The laser
was operated multimode with a uniform beam
profile. At the tip, the laser beam was coupled
into a zirconium fluoride fiber of 600 microns
core diameter. The tip was used in contact mode
to fracture and emulsify the nucleus. The energy
per pulse delivered through the fiber was
measured with a joule meter (PEM 10) at its high
sensitivity of 81.5V/J. The fluence per pulse was
calculated from energy per pulse and the measured
spot diameter. The fluence was regulated by
changing of the bank voltage. Parameters were
energy of 35 mJ, repetition rate of 3 Hz and a
puls length of 250 µs.   The lens fragments
from 3 patients were used according to
conventional method. The fragments of the lenses
as well as the BSS liquid with rests of Healon
GV were caught in a bag after ultrasound phaco.
The samples were divided in each case in
equal parts and a proportion was treated once
with the ErYAG laser. The untreated sample
served as reference.   Analysis The analysis of
the burn-up products was executed at a gas
chromatograph and mass spectrograph. For this
first screening a non polar column was
used.   Results This first screening points
showed a modification of the determined data
from untreated material (Fig.1) to treated
material (Fig.2). This modification could be
observed in each case with the samples of
the 3 patients. The data of the laser treated
sample showed additional various, different
masses could be detected. These mass
numbers (Fig.3,5) are representing substances in
the samples were detected. The measurements of
the treated samples showed the same spectral mass
again almost on the following day as the
untreated samples (Fig.6-8).     Conclusion The
results of this investigation do not permit a
conclusion over poisonous of the detected
substances especially not an clinical reaction.
The measurements with polar columns necessarily
enable a very narrow-band detection of individual
chemical products. The investigation allows the
statement that the detected substances are
short-lived or volatile. A precise investigation
of the detected substances is necessary to
exclude the toxicologically potential of these
laser induced products.
University of Heidelberg Department of
Ophthalmology INF 400, D-69120 Heidelberg
Germany E-mailHolger_Specht_at_med.uni-Heidelberg.de
ASCRS American Sociaty of Cataract and
Refractive Surgery 2001

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