Presidential Greeting - American Society for Laser Medicine and ...

4 American Society for Laser Medicine and Surgery Abstracts
Conclusion: These results indicate that subcurative PDT doses
lead to induction of SDF-1a/CXCR4 expression and increased
levels of CECs and CEPs. Studies are currently underway to
examine if CEC and CEP levels can be used as biomarkers of PDT
response and to determine if preventing CEP mobilization and
incorporation into tumor vasculature can, by blocking
angiogenesis, improve PDT responsiveness.
#9
COMPARISON OF ANTIANGIOGENIC AGENTS
FOR INHIBITING REPERFUSION OF
PHOTOCOAGULATED BLOOD VESSELS IN AN
ANIMAL MODEL
Wangcun Jia, Victor Sun, Tom Liu, Bernard Choi,
J. Stuart Nelson
Beckman Laser Institute and Medical Clinic, University of
California, Irvine, CA; Conrex Pharmaceuticals, Newtown
Square, PA
Background: Antiangiogenic agents have been demonstrated to
reduce the reperfusion of photocoagulated blood vessels with
varying degrees of success, which might improve the therapeutic
efficacy of port wine stain laser treatment. Our objective was to
compare the safety and efficacy of different antiangiogenic agents
for preventing photocoagulated blood vessels from reperfusing.
Study: Two macrolide lactones, rapamycin and tacrolimus were
tested in this study. Rapamycin is a specific mTOR inhibitor and
tacrolimus is a calcineurin/NFAT inhibitor. Both agents were
formulated as topical ointments which contained 1% effective
ingredient, solvent, medical base and a skin penetration
enhancer. The animal model was the dorsal skinfold window
chamber on hamster. Immediately after laser irradiation of blood
vessels in the window, a topical antiangiogenic agent was applied
to the epidermal side of the window daily for 14 days. Color digital
photography and laser speckle imaging were used to document
structure and flow dynamics of blood vessels.
Results: The reperfusion rate was reduced from nearly 100% for
control (laser irradiation only) to 39% and 78% for rapamycin and
tacrolimus, respectively. Skin irritation was observed on animals
treated with tacrolimus. It was also noted that efficacy varied
significantly among animals treated with the combined therapy.
Conclusion: More antiangiogenic agents need to be screened to
determine the best candidate for combined laser and topical antiangiogenic
therapy for port wine stain and other cutaneous
vascular lesions, which is currently being pursued in our lab.
#10
INFLUENCE OF PULSE DURATION ON
EFFICIENCY AND SOME ADVERSE EFFECTS OF
ND:YAG LASER IRIDOTOMY
Gregor Hawlina, Brigita Drnovsek-Olup
Eye Clinic, University Medical Centre, Ljubljana Ljubljana,
Slovenia
Background: Most common adverse effects following Nd:YAG
laser iridotomy are intraocular pressure elevation, reduction of
endothelial cell count, cystoid macular edema, retinal rupture/
detachment and acceleration of cataract. The causes of some
adverse effects are still poorly understood, but they are more
frequent when using laser pulses of higher energy level.
Photodisruptors trigger laser induced breakdown (LIB) by
transferring very high energy on very small area in focal region.
LIB has characteristics of microexplosion and is accompanied by
two secondary phenomena: cavitation bubble and high energy
pressure wave. In ophthalmic microsurgical procedures
amplitude of high energy pressure wave determines the area of
potential damage of nearby tissue, while the size of cavitation
bubble is proportional to removal of unwanted eye tissue. The area
of LIB in eye is small, but surrounded by many fragile structures.
These structures could be damaged by microexplosion itself or by
secondary effects which could damage more extensive area. The
size of area of mentioned laser effects is directly proportional to
laser pulse energy. Lower laser pulse energy level should
therefore lower the possibility of injuries of surrounding
structures.
Study: In the first part LIB and secondary effects in the water
and porcine vitreous following use of photodisruptor with pulse
duration of 5 nanoseconds and new model with pulse duration of
near 1 nanosecond is studied. In the second part we are comparing
number of pulses, average and total energy needed to create an
open iridotomy on animal model (porcine iris).
Results: Nd:YAG laser with shorter pulse duration needs almost
the same acting power but less energy to reach threshold for laser
induced breakdown (LIB). Consecutively the size of cavitation
bubble and amplitude of high energy pressure wave is smaller. To
create an open iridotomy on porcine iris Nd:YAG laser with
shorter pulse duration needs lower energy of one pulse and less
total energy.
Conclusion: Recently developed photodisruptor based on
Nd:YAG laser enables shorter pulse duration and consecutively
lower energy level while performing ophthalmic laser procedures.
Ophthalmic laser procedures made by this laser should be safer
with less adverse effects.
#11
EFFECTS OF LASER BEAM MODIFICATION ON
THE ANTERIOR CHAMBER ANGLE STRUCTURAL
CHANGES AFTER SELECTIVE LASER
TRABECULOPLASTY IN ANIMAL MODEL
Rok Grcar, Brigita Drnovsek-Olup
Eye Hospital Ljubljana, Ljubljana, Slovenia
Background: Selective laser trabeculoplasty (SLT) is a relatively
new, efficient and safe method for reduction of intraocular
pressure in patient with glaucoma and ocular hypertension.
Histological analysis of human anterior chamber angle after SLT
showed absence of coagulative necrosis and minor trabecular
meshwork (TM) damage. After SLT, TM endothelial cells secrete
certain cytokines and metalloproteinases which increase
trabecular meshwork fluid permeability resulting in intraocular
pressure reduction. The effects of laser beam or its modifications
on structural changes of the anterior chamber angle and the
mechanism of intraocular pressure reduction are not yet known.
Study: The effect of laser beam modification on the anterior
chamber angle structural changes in an animal model (porcine
eyes) is studied with transmission electron microscopy. The effect
of new parameters with more constant power density profile is
compared to the standard SLT parameters, where laser beam with
power density profile similar to Gaussian curve is used.
Results: Modified laser beam with more constant power density
profile induces less damage to the trabecular meshwork than
classic laser beam with power density profile similar to Gaussian
curve.
Conclusion: Modified laser beam with more constant profile is
expected to deliver energy more evenly to the treated area and to