Download Anterior chamber gas bubbles after corneal flap creation with a

J CATARACT REFRACT SURG - VOL 31, NOVEMBER 2005
Anterior chamber gas bubbles after corneal
flap creation with a femtosecond laser
Tova Lifshitz, MD, Jaime Levy, MD, Itamar Klemperer, MD, Shmuel Levinger, MD
A 48-year-old woman had bilateral wavefront-guided laser in situ keratomileusis for myopia with
IntraLase corneal flap creation. In the right eye the cavitation bubbles were observed not only in
the interface between the flap and the corneal bed but also in the anterior chamber disappearing
after 30 minutes. After the procedure, uncorrected visual acuity is 20/25 in both eyes; and specular microscopy shows normal hexagonal cells and density. Although no postoperative complications were observed in our case, further follow-up is needed to examine the long-term effect of
this phenomenon of IntraLase.
J Cataract Refract Surg 2005; 31:2227–2229 Q 2005 ASCRS and ESCRS
During the past 5 years, several reports have described the
results in laboratory and clinical settings of the femtosecond laser for the creation of a corneal flap in laser in situ
keratomileusis (LASIK) procedures and its advantages
over current microkeratome systems.1–6 These reported advantages include the creation of more predictable flap dimensions, the use of low vacuum during suction, and the
theoretical elimination of intraoperative flap complications
such as incomplete flap, buttonhole perforation, and unpredictable thickness.2–4,6 In essence, the femtosecond
laser is focused on a predetermined depth within the
corneal stroma, delivering pulses of light in a raster pattern,
creating focused cavitation spots within the stroma that will
expand and result in a resection plane. Cavitation bubbles
representing carbon dioxide and water can appear not only
underneath the flap but also in the pocket, behind the
hinge, and sometimes in the episclera or in the circumferential host tissue. After several seconds to minutes, the bubbles disappear and a standard LASIK procedure can be
performed.
Accepted for publication December 2, 2004.
From the Department of Ophthalmology (Lifshitz, Levy, Klemperer), Soroka University Medical Center, Ben-Gurion University
of the Negev, Beer-Sheva, Israel, and ‘‘Enaim’’ Ophthalmological
Center (Lifshitz, Klemperer, Levinger), Jerusalem, Israel.
No author has a financial or proprietary interest in any material or
method mentioned.
Reprint requests to Jaime Levy, MD, Department of Ophthalmology, Soroka University Medical Center, P.O. Box 151, Beer-Sheva
84101, Israel. E-mail: [email protected].
Q 2005 ASCRS and ESCRS
Published by Elsevier Inc.
Bubbles appearing in the anterior chamber are a known
and infrequent complication during flap creation with
a femtosecond laser, but to our knowledge they have not
been reported in the literature. We describe the first
reported case in the literature of bubbles in the anterior
chamber during corneal flap creation with a femtosecond
laser. No postoperative complications were observed.
CASE REPORT
A 48-year-old woman sought refractive surgery to correct
myopia. The patient’s ocular history was unremarkable, with no
history of contact lens wear. The uncorrected visual acuity
(UCVA) was 20/200 in both eyes, the best spectacle-corrected visual acuity was 20/20 in the right eye and 20/25 in the left eye
with a refraction of ÿ5.25 ÿ2.50 15 in the right eye and
ÿ5.25 ÿ2.25 171 in the left eye. Central keratometry (Canon
RK-2) measured 44.25 in both eyes, in the right eye and
44.50@171/47.00@81 in the left eye. Preoperative ultrasound pachymetry (Nidek US-1800, 10 MHz frequency) was 534 mm in the
right eye and 540 mm in the left eye. Preoperative corneal topography and Orbscan (Bausch & Lomb) showed abnormalities in the
posterior float or the thickness map.
Before surgery, the patient received a full explanation of
the procedure and a written informed consent was obtained.
The patient had a bilateral wavefront-guided (Zyoptix Keracor
217, Bausch & Lomb) LASIK with IntraLase (IntraLase Corp.)
corneal flap creation. A myopic final refraction was targeted for
monovision. With an eyelid speculum, the eye was fixated with
the standard IntraLase patient interface suction fixation ring.
The IntraLase computer settings were a planned flap thickness
of 100 mm, a planned flap diameter of 9.0 mm, a hinge angle of
45 degrees, raster energy of 2.2 mJ, beam separation of 11 mm,
line separation of 9 mm, and a side-cut energy of 4.0 mJ. A superior
pocket of 290 mm depth was created. The cornea was applanated
with the disposable glass contact lens cone attached to the suction
ring via an internal clamp. Following creation of the flap, the suction ring was released and the applanating contact lens was
0886-3350/05/$-see front matter
doi:10.1016/j.jcrs.2004.12.069
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CASE REPORTS: LIFSHITZ
removed. In the right eye, cavitation bubbles were observed not
only in the interface and corneal stroma but also in the anterior
chamber (Figure 1) and the flap was then lifted. Flap lifting was
uneventful in the left eye. It was decided to continue with the laser
treatment. The intended refraction was ÿ3.75 ÿ2.13 18 in the
right eye and ÿ4.72 ÿ1.77 168 in the left eye. During the laser
ablation in the right eye, the eyetracker had difficulty in detecting
the center of the pupil owing to the bubbles in the anterior chamber and it had to be realigned several times. The procedure was
eventually completed successfully. The cavitation bubbles disappeared after about 30 minutes. This was the only case with bubbles
in the anterior chamber observed in our center after several hundred procedures.
One day after LASIK, the UCVA was 20/30 in both eyes
with bilateral clear corneas, improving to 20/25 in both eyes after
1 week. Three months after the procedure, the UCVA was 20/25
in both eyes. Specular microscopy 1 week and 1 month after
the procedure revealed normal hexagonal cells and density of
2850 cells/mm2 in the right eye and 2629 cells/mm2 in the left eye.
DISCUSSION
More than 100 000 procedures worldwide have been
performed with the IntraLase technology (IntraLase
Corp. data, July 2004). Data on file of complications include thin flaps, perforations of the flap with flap elevation
instruments, and the dispersion of gas bubbles from the interface through the anterior stroma via defects in Bowman’s
layer into the subepithelial space interfering with additional laser treatment.
The near-infrared neodynium-glass laser pulse
(1053 nm) passes through the superficial corneal tissue
unabsorbed, unlike argon–fluoride excimer lasers, until it
is focused to a small spot size at a desire depth.1 When
the laser pulse reaches this focal point, a process called
Figure 1. Intraoperative photograph of the right eye after the creation of
the flap with the IntraLase. Cavitation bubbles can be observed in the
anterior chamber.
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laser-induced optical breakdown is initiated.1,2 Due to
plasma ignition and its explosive expansion, a shockwave is generated. In media with high aqueous saturation,
such as the cornea, a vapor-filled bubble develops at the
breakdown region without interfering with surface cell
layers.1,2,5 Due to the photodissociation of involved water,
the bubble contains hydrogen. Femtosecond laser–induced
optical breakdown requires very low energy and produces
virtually no thermal damage or shockwave transmission
to surrounding tissue. The spots are placed 5 to 12 mm apart
side to side6 and 7 to 15 mm in front of each other (line separation). As the microcavitation bubbles expand, the spots
coalesce, forming a resection plane. The byproducts are
carbon dioxide and water, which are absorbed by the action
of the endothelial pump. The created bubbles may remain
within the stroma for several seconds to minutes and can
interfere with subsequent laser pulses. If 2 successive laser
pulses are placed too close to each other, the produced bubbles merge, leading to large intrastromal bubbles that will
deflect following laser pulses, resulting in remaining tissue
bridges.5 To overcome this problem, the pulses of very low
energy threshold are delivered in a raster pattern, resulting
in microcavitation bubbles and allowing nearly contiguous
placement of laser pulses without almost collateral shockwave effects.
The reported histologic data of corneas after femtosecond corneal flap creation show that with pulse energy of
4 mJ and spot separation of 15 mJ, the tissue effects are
minor, with bubbles in the anterior stroma created by the
merging of many single bubbles, in which there is loose
collagen debris.1 Up to the present and with the reported
laboratory data, the exact dynamics of the bubbles and their
interaction is not fully understood. In this case, the IntraLase initial settings were similar to those previously
reported.3,6 We speculate that many small bubbles coalesced and created larger bubbles that migrated through
the posterior stroma and endothelium without being absorbed by the endothelial pump, and these bubbles appeared in the anterior chamber. Theoretically, the laser
shockwave might push the air bubbles posteriorly, and if
stromal lamellae are weak or endothelial junctions are
not too tight, the bubbles can appear in the anterior chamber. Large bubbles could also be created near the pocket
and then would migrate to the posterior stroma and anterior chamber. Another mechanism might be a retrograde
passage of the bubbles from the perilimbal area to the trabecular meshwork into the anterior chamber.
During the wavefront-guided laser procedure, the eyetracker was unable to follow the pupil because of the presence of the bubbles in the anterior chamber. In this case, the
bubbles disappeared after about 30 minutes, so it is advisable to wait for spontaneous resolution of the bubbles before starting with the excimer laser procedure.
J CATARACT REFRACT SURG - VOL 31, NOVEMBER 2005
CASE REPORTS: LIFSHITZ
Future laboratory investigations are needed to examine possible endothelial damage after femtosecond corneal
flap creation in refractive surgery and to clarify whether
preoperative endothelial anomalies can predispose to the
presence of cavitation bubbles in the anterior chamber.
REFERENCES
1. Lubatschowski H, Maatz G, Heisterkamp A, et al. Application of ultrashort laser pulses for intrastromal refractive surgery. Graefes Arch
Clin Exp Ophthalmol 2000; 238:33–39
2. Sugar A. Ultrafast (femtosecond) laser refractive surgery. Curr Opin
Ophthalmol 2002; 13:246–249
3. Nordan LT, Slade SG, Baker RN, et al. Femtosecond laser flap creation
for laser in situ keratomileusis: six-month follow-up of initial U.S. clinical
series. J Refract Surg 2003; 19:8–14
4. Ratkay-Traub I, Ferincz IE, Juhasz T, et al. First clinical results with the
femtosecond neodymium-glass laser in refractive surgery. J Refract
Surg 2003; 19:94–103
5. Heisterkamp A, Mamom T, Kermani O, et al. Intrastromal refractive
surgery with ultrashort laser pulses: in vivo study on the rabbit eye.
Graefes Arch Clin Exp Ophthalmol 2003; 241:511–517
6. Binder PS. Flap dimensions created with the IntraLase FS laser. J Cataract Refract Surg 2004; 30:26–32
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