Allopatric Femtosecond Laser Air Bubble Formation in a Closed System

1
Allopatric Femtosecond Laser Air Bubble Formation
in a Closed System

• Dan Driscoll, MD
• Takeshi Ide, MD, PhD Sonia H Yoo, MD
• Richard K Lee, MD, PhD Terrence P O'Brien, MD
• Bascom Palmer Eye InstituteMiami, FL

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Background

• Allopatric air bubble formation happens rarely in
  femtosecond laser-assisted surgeries
• Potential complications of air bubbles
• Impaired suction of laser applanator
• Poor intraoperative pachymetry
• Poor ablation efficiency
• Difficulty with eye tracking and iris
  registration for excimer laser

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Traditionally-held hypothesis for formation

• Possibly from air traveling via an intralamellar
  network to various intraocular locations
• trabecular meshwork
• corneal stroma
• endothelium
• Possibly migration of small bubbles through the
  posterior stroma and endothelium without being
  absorbed by the endothelial pump

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Materials and Methods

• Balanced Salt Solution (BSS) bottles completely
  filled and capped, verified not to contain air
• Optical Coherence Tomography (OCT) was used to
  determine the thickness of the BSS bottle wall.
• Thickness determined to be 500-550 µm

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Materials and Methods

• Single drop of BSS applied to the bottle surface
• Glass applanator then applied without suction
  ring
• 5 bottles sampled for IntraLase flap mode cuts
• Flap Settings 8.5 mm diameter, 180 µm depth, 1.9
  µJ bed energy, 2.3 µJ sidecut energy, 11 µm spot
  separation, 9 µm line separation, 70 degree
  sidecut angle
• Results photographed and measured with Visante OCT

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Results

• Many bubbles formed in the BSS drop on the
  surface of the bottle in the areas peripheral to
  the applanated zone.
• During the laser cutting into the bottle wall,
  many tiny air bubbles gradually appeared inside
  the BSS bottle.
• No cuts crossed the inner wall of the BSS
  bottles.

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• In-the-Bottle Air bubble. The air bubbles could
  be seen clearly under the microscope

8

• OCT image of BSS bottle. IntraLase cut lines in
  the wall of BSS bottle could be
• seen clearly under the OCT and no cut crossed the
  inner wall of the BSS bottles.

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Discussion

• No observations clinically of air bubbles in the
  deep stroma or outside the flap in vivo.
• Lends discourse to air traveling through the
  trabecular meshwork, corneal stroma, and
  endothelium.
• Additionally, bubbles initially form centrally
  and not adjacent to lamellar pocket, which would
  be expected if TM theory were true.
• Bubbles were consistently able to be produced in
  the closed BSS bottle system with a deeper cut
  (180 µm) but were not able to be produced with a
  120 µm cut.

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Proposed mechanism of air bubble formation in
closed system

• Production allopatric cavitation bubbles in the
  eye from the vibration of cutting and suction
  pressure
• Similar to cavitation bubbles formed from
  phacoemulsification
• Actual physics behind mechanism still under
  investigation

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Conclusion

• Experimental system of BSS bottles does not equal
  in vivo characteristics of the human eye.
• Further research necessary into determining exact
  mechanism of air bubble formation during
  femtosecond laser application to a closed system.

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References and Acknowledgements

• Primary investigator for this project was Takeshi
  Ide, MD, PhD under the direction of Sonia Yoo, MD
  of the Bascom Palmer Eye Institute
• 1. Nordan LT, Slade SG, Baker RN, Suarez C,
  Juhasz T, Kurtz R. Femtosecond laser flap
  creation for laser in situ keratomileusis
  six-month follow-up of initial U.S. clinical
  series. J Refract Surg. 2003198-14.
• 2. Seiler T, Koufala K, Richter G. Iatrogenic
  keratectasia after laser in situ keratomileusis.
  J Refract Surg. 199814312-317.
• 3. Genth U, Mrochen M, Walti R, Salaheldine MM,
  Seiler T. Optical low coherence reflectometry for
  noncontact measurements of flap thickness during
  laser in situ keratomileusis. Ophthalmology.
  2002109973-978.
• 4. Probst LE, Machat JJ. Mathematics of laser in
  situ keratomileusis for high myopia. J Cataract
  Refract Surg. 199824190-195.
• 5. Seider MI, Ide T, Kymionis GD, Culbertson WW,
  O'Brien TP, Yoo SH. Epithelial breakthrough
  during IntraLase flap creation for laser in situ
  keratomileusis. J Cataract Refract Surg.
  200834859-63.
• 6. Kaiserman I, Maresky HS, Bahar I, Rootman
  DS.Incidence, possible risk factors, and
  potential effects of an opaque bubble layer
  created by a femtosecond laser. J Cataract
  Refract Surg. 200834417-23.
• 7. Ide T, Kymionis GD, Goldman DA, Yoo SH,
  OBrien TP. Subconjunctival Gas Bubble Formation
  During LASIK Flap Creation Using Femtosecond
  Laser. J Refract Surg IN
• 8. Kuo AN, Kim T. Persistent anterior chamber gas
  bubbles during IntraLASIK. J Cataract Refract
  Surg. 2007331134-5.
• 9. Lifshitz T, Levy J, Klemperer I, Levinger
  S.Anterior chamber gas bubbles after corneal flap
  creation with a femtosecond laser. J Cataract
  Refract Surg. 2005312227-9. 10. Wright JR. Gas
  bubbles after flap creation with femtosecond
  laser. J Cataract Refract
• Surg. 2006321076.
• 11. Srinivasan S, Rootman DS. Anterior chamber
  gas bubble formation during femtosecond laser
  flap creation for LASIK. J Refract Surg.
  200723828-30.
• 12. Cumberbatch E. Self-focusing in Non-linear
  Optics IMA J Appl Math 1970 6 250-262
• 13. Mourou GA, Tajima T, Bulanov SV. Optics in
  the relativistic regime. Rev. Mod. Phys. 200678
  309371.
• 14. Zacharias J. Role of cavitation in the
  phacoemulsification process. J Cataract Refract
  Surg. 2008 May34846-52.