Download Ocular Coherence Tomography-Guided and Femtosecond Laser

Ocular Coherence Tomography-Guided and Femtosecond
Laser-Assisted Deep Anterior Lamellar Keratectomy in an
Ex-Vivo Model
CONFLICT OF INTEREST:
AUTHORS,
1.
Saeed Motowa, MD
• Authors have no financial interests in
the subject matter of this poster.
Senior Academic Consultant, KKESH
2. Reem Al-Huthail, MD
cornea , external disease and refractive surgery fellow,
KKESH
3. William May, MD
Senior academic consultant.
Chief , cornea , external disease and
surgery division
refractive
• Thanks to ALCON for providing the
patient interfaces used in this
experiment.
Big Bubble Technique of Deep Anterior
Lamellar Keratoplasty
• First described by Anwar and Teischman in 2002 as a result
of their work at our institution in Saudi Arabia.
• Allows separation by cleavage between Decemet’s
membrane and posterior stroma by injection of air in deep
stroma to bare the Decment’s membrane in the recipient
cornea.
• Big bubble formation was achieved in up to 90% of cases by
Anwar and Teischman.
Anwar M1, Teichmann KD. Big-bubble technique to bare Descemet's membrane in anterior lamellar keratoplasty. J Cataract Refract Surg.
2002 Mar;28(3):398-403.
3 things may happen at air injection. 2 of them
are bad
• Air may go into cornea causing complete opacification.
• Air may enter the anterior chamber indicating perforation of
Decemet’s membrane.
• The big bubble forms indicating successful separation.
• Accurate depth of needle placement is necessary to avoid
undesirable stromal opacification by air or perforation.
General goal of femtosecond laser
• Is focusable infrared laser , which utilizes pulses in the
femtosecond duration range.
• Contiguous pulses are placed at a precise depth within the cornea.
• The 1053 nm wavelength of the light used by the laser is
transparent to the cornea , thus resecting only targeted tissue,
while leaving surrounding tissue unaffected.
• Vaporizes small volumes of tissue by photo disruption, producing
plasma , a shock wave , cavitation and gas ( CO2 and H2O )
Bubbles.
Mian SI1, Shtein RM. Femtosecond laser-assisted corneal surgery. Curr Opin Ophthalmol. 2007 Jul;18(4):295-9.
New surgical approach (methods)
• We purposefully used the femtosecond laser in conjunction with OCT to create a gas
filled space deep in the corneal stroma adjacent to Decement’s membrane in eye bank
eyes.
• The linear primary incision program of the LensEx femtosecond laser was used to
make a linear incision.
• The energy was set at less than 5 µJ and the spot separation and line separation were
set at 3 um.
• We used the small bubbles to guide needle placement.
• When the tip of the needle started to move the bubbles injection was made.
• The gas filled space can be visualized at the operating microscope , allowing accurate
needle placement and consistent separation of Decement’s membrane with air
infusion .
ALCON LensEx laser primary incision
parameters
The eye bank eye was
then docked and imaged.
The incision position was
moved as close to the
center of the cornea as
the software would allow
and shortened as much
as the software would
allow.
The gates limiting superior and
inferior
treatments
were
adjusted as follows. The
inferior gate was elevated to a
point just above Decemet”s
membrane.
Decemets
membrane was placed as a
tangent line to the adjustment
dot. The superior treatment
limit (gate) was brought as
close as the software would
allow to the inferior gate.
After treatment the eye
bank eye was re-docked
to the laser and OCT
imaging was done as if a
new treatment were
being performed. The
imaging was done along
the 180 degree meridian
where
the
previous
treatment
had
been
performed. This allowed
the imaging of the
recently treated area TO
SHOW
DEEP
INTRASTROMAL
GAS
FILLED SPACE
A 30 gauge needle was used to reach this space. When
the needle arrived at the treatment zone, bubble
movement was noted. Injection of air was done at this
point.
Successful separation of Decemet’s
membrane from the corneal stroma
with air infusion.
After air and viscoelastic INJECTION.
The eye was taken back to the laser
and re-docked. OCT imaging was
again performed.
Results and summary
• We used this technique to create the big bubble in 4 eye bank
eyes.
• OCT guided femtosecond laser application may be used to
accurately mark the deep corneal stroma.
• The arrival of the needle tip moves the small bubbles and
indicates accurate needle placement.
• This technique may improve success of big bubble formation in
DALK.