Allopatric Femtosecond Laser Air Allopatric Femtosecond Laser Air Bubble Formation in a Closed SystemBubble 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

Takeshi Ide, MD:  research for KANEKA O'Brien, Terrence, MD: consultant for AMO, Alcon, Allergan, B&L, Inspire Pharmaceuticals, Ista Pharmaceuticals Sirion Therapeutics, and Vistakon PharmaceuticalsSonia Yoo, MD: consultant for Alcon; research for Carl Zeiss Meditec; travel expenses by IntraLase CorpationNone of the authors have a propriety interest in this study.

BackgroundBackground• Allopatric air bubble formation happens rarely in Allopatric air bubble formation happens rarely in

femtosecond laser-assisted surgeriesfemtosecond laser-assisted surgeries

• Potential complications of air bubbles:Potential complications of air bubbles:– Impaired suction of laser applanatorImpaired suction of laser applanator– Poor intraoperative pachymetryPoor intraoperative pachymetry– Poor ablation efficiencyPoor ablation efficiency– Difficulty with eye tracking and iris registration for Difficulty with eye tracking and iris registration for

excimer laserexcimer laser

Traditionally-held hypothesis for Traditionally-held hypothesis for formationformation

• Possibly from air traveling via an intralamellar Possibly from air traveling via an intralamellar network to various intraocular locations:network to various intraocular locations:– trabecular meshwork trabecular meshwork – corneal stroma corneal stroma – endotheliumendothelium

• Possibly migration of small bubbles through the Possibly migration of small bubbles through the posterior stroma and endothelium without being posterior stroma and endothelium without being absorbed by the endothelial pumpabsorbed by the endothelial pump

Materials and MethodsMaterials and Methods• Balanced Salt Solution (BSS) bottles completely Balanced Salt Solution (BSS) bottles completely

filled and capped, verified not to contain airfilled and capped, verified not to contain air

• Optical Coherence Tomography (OCT) was used to Optical Coherence Tomography (OCT) was used to determine the thickness of the BSS bottle wall.determine the thickness of the BSS bottle wall.– Thickness determined to be 500-550 µmThickness determined to be 500-550 µm

Materials and MethodsMaterials and Methods• Single drop of BSS applied to the bottle surfaceSingle drop of BSS applied to the bottle surface

• Glass applanator then applied without suction ringGlass applanator then applied without suction ring

• 5 bottles sampled for IntraLase flap mode cuts5 bottles sampled for IntraLase flap mode cuts– Flap Settings: 8.5 mm diameter, 180 µm depth, 1.9 µJ Flap Settings: 8.5 mm diameter, 180 µm depth, 1.9 µJ

bed energy, 2.3 µJ sidecut energy, 11 µm spot separation, bed energy, 2.3 µJ sidecut energy, 11 µm spot separation, 9 µm line separation, 70 degree sidecut angle9 µm line separation, 70 degree sidecut angle

• Results photographed and measured with Visante Results photographed and measured with Visante OCTOCT

ResultsResults• Many bubbles formed in the BSS drop on the Many bubbles formed in the BSS drop on the

surfacesurface of the bottle in the areas peripheral to the of the bottle in the areas peripheral to the applanated zone. applanated zone.

• During the laser cutting into the bottle wall, many During the laser cutting into the bottle wall, many tiny air bubbles gradually appeared inside the BSS tiny air bubbles gradually appeared inside the BSS bottle. bottle.

• No cuts crossed the inner wall of the BSS bottles. No cuts crossed the inner wall of the BSS bottles.

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

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

DiscussionDiscussion• No observations clinically of air bubbles in the deep stroma No observations clinically of air bubbles in the deep stroma

or outside the flap or outside the flap in vivoin vivo. . – Lends discourse to air traveling through the trabecular meshwork, Lends discourse to air traveling through the trabecular meshwork,

corneal stroma, and endothelium. corneal stroma, and endothelium. – Additionally, bubbles initially form centrally and not adjacent to Additionally, bubbles initially form centrally and not adjacent to

lamellar pocket, which would be expected if TM theory were true. lamellar pocket, which would be expected if TM theory were true.

• Bubbles were consistently able to be produced in the closed Bubbles were consistently able to be produced in the closed BSS bottle system with a deeper cut (180 µm) but were not BSS bottle system with a deeper cut (180 µm) but were not able to be produced with a 120 µm cut. able to be produced with a 120 µm cut.

Proposed mechanism of air bubble Proposed mechanism of air bubble formation in closed systemformation in closed system

• Production allopatric cavitation bubbles in the eye Production allopatric cavitation bubbles in the eye from the vibration of cutting and suction pressurefrom the vibration of cutting and suction pressure– Similar to cavitation bubbles formed from Similar to cavitation bubbles formed from

phacoemulsificationphacoemulsification

• Actual physics behind mechanism still under Actual physics behind mechanism still under investigationinvestigation

ConclusionConclusion

• Experimental system of BSS bottles does not equal Experimental system of BSS bottles does not equal in vivoin vivo characteristics of the human eye. characteristics of the human eye.

• Further research necessary into determining exact Further research necessary into determining exact mechanism of air bubble formation during mechanism of air bubble formation during femtosecond laser application to a closed system.femtosecond laser application to a closed system.

References and AcknowledgementsReferences and AcknowledgementsPrimary investigator for this project was Takeshi Ide, MD, PhD under the direction of Sonia Yoo, MD of the Primary investigator for this project was Takeshi Ide, MD, PhD under the direction of Sonia Yoo, MD of the

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