presbyopia athens - university of...
TRANSCRIPT
H. LubatschowskiT. Ripken, U. Oberheide, C. Ziltz, G. Gerten
Femtosecond Laser Applicationsin the Huaman Lens
presbyopia
material & methods
lens cutting precision
deformation ability
fs-laser induced elasticity changes to improve presbyopic lens accommodation
Presbyopia - preconditions
Helmholtz theory accommodation failure because of:
• loss of lens elasticity
• tissue hardening inside the lens
however:• ciliary muscle
stays activ• lens capsule
stays elastic
• overcome lens-hardening• regain lens elasticity
Treatment conception
smooth µm cuts inside thecrystalline lens
fs LASIK
1 mm1 mmlens tissue
fs laserpulse
Ray Myers and Ron Krueger first reported on the concept of laser modification of the crystalline lens in 1998.
Treatment conception
First experimental results 2001 by Krueger et.al. with ns-pulses
Accomodative Potential after Nd:YAG Laser Photodisruption, Ophthalmology 2001
• 2.5 to 7 mJ pulse energy
• increased elasticity of 11 lens pairs
• too large residual bubbles (increaseof volume / light scattering)
Cutting effect: Photodisruption
1-5 µm
focussed fs laser beam
nonlinear absorption
plasma
shock wave
cavitation bubble
gas bubble
Laser induced cavitation and bubble formation in water
Laser PulseEpuls ~ 4µJτpuls ~ 160fs
Bright System Thales
Ultrashort pulse lasersystem
diode-pumped Nd:YLFIMRA fs-oscillatorTi:Sa-regen and doublepass
150 fs l 5 kHz l 1.5 W l 780 nm
Scanner & Suction Unit
suction unit
• scanner positions in x-y-plane • eye-fixation with lightly depressure• suction unit translates in z-direction• f-theta-optic• accuracy approx. 1 µm• focal spot approx. 5 µm
Influence of laser parameters
2 µJ 4 µJ
5 µm
7 µm
9 µm
frontal cut
parameter:• number of rings• cutting width• cutting depth• spot separation• pulse energy
samples: ex vivo pig-eyes
immediatly enucleatedtreatment within 6 hours
Testing simple geometric patterns inside the lens
cylindricstar-likeannular combined orsteering-wheel
pattern
pulse energy 680 nJrepetition rate 5 kHzpulse duration 150 fsspot separation 5 µm
star-like, annular and cylindrical cutin a pig lenspulse energy about 830 nJ
Steering wheel pattern
arbritrary• height• inner and outer diameter• number of planes• spot separation
off-axis angle
• Decrease of pulse energy from 1 µJ down to 400 nJ
• Cutting of 'sagittal' patterns with an off-axis angle (conical cuts)
Optimizing the cutting precision
PAA samplepulse energy: 1.4 µJspot separation: ∆x und ∆z = 5 µm
cylindrical cutoff-axis angle 0°
conical cutoff-axis angle 30°
conical cutoff-axis angle 45°
decreasing of bubble size
Optimizing the precision: off-axis angle
pulse energy 0.52 µJ
spot separation ∆x and ∆z = 5 µm
less
bubble
s
cylindrical cut
30° off-axis angle
45° off-a
xisangle
Pig lens histological section
Optimizing the precision: off-axis angle
• Decrease of pulse energy from 1 µJ to 400 nJ
• Increasing of spot separation in sagittal cuts
• Cutting of „sagittal“ patterns with an off-axis angle
Optimizing the cutting precision
pulse energy: 1.4 µJ
spot separation: ∆x = 5 µm
a) ∆z = 5 µm
b) ∆z = 10 µm
c) ∆z = 20 µm
d) ∆z = 40 µm
PAA sample
less
bubble
sOptimizing the precision: spot separation
a) 0 rpm
Lens deformation ability changes - setup
rotation stage
CCD-camera
c) 1850 rpmb) 1035 rpm
Comparison of treated and untreated pig lenses
Lens deformation ability changes
hig
her
def
orm
atio
nab
ility
average of 60 lensesone pig lens
20% increase of ability of lens deformation
• NIR-fs-photodisruption enables 3D-cuts inside the lens
• easy procedure, no visual side-effects appear (ex vivo)
• improvement in frontal cuts
• microcuts increase lens deformation ability
Summary
Outlook• need of measuring the regain of elasticity in prespyobic lenses
• optimization of cutting patterns with respect to an elasticity maximum
• further investigations on lens biomechanics
• in vivo studies
Fs-laser induced elasticity changes to improve presbyopic lens accommodation
Holger [email protected] www.lzh.de