Femtosecond Assisted Descemet Stripping Automated Endothelial Keratoplasty (DSAEK) Donor Tissue Preparation

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Femtosecond Assisted Descemet Stripping Automated
Endothelial Keratoplasty (DSAEK) Donor Tissue
Preparation
Natalie Stanciu, MD Richard M. Awdeh, MD Takeshi
Ide, MD Sonia Yoo, MD Bascom Palmer Eye
Institute ASCRS 2009 San Francisco
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Background

• 45,000 PKP are performed annually in the US, 45
  include cases of corneal damage limited to
  endothelium.
• DSAEK popular alternative to PKP.
• Most DSAEK tissue is cut with microkeratome
• Limitations of microkeratome inability to
• control the thickness and shape of donor tissue.
• One potential reason why BCVA after DSAEK rarely
  20/20.

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Background

• Recently the use of Femtosecond laser has been
  entertained as an alternative to mechanical
  mickrokeratome.
• Advantage Ability to control thickness and
  predictable shape.
• Challenge is achieving smooth surface
• a problem less encountered by microkeratome.

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Interface Issue
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Hypothesis

• Variables which can affect smoothness
• Low vs. High Energy
• Single vs. Multiple Pass
• Laser pattern Raster vs. Spiral
• In this pilot study, we compared relative
  smoothness of femtosecond-cut tissue using
  several different combinations of above
  variables.
• We predict that Raster, Low, Multiple pass should
  produce the smoothest surface.

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Laser Settings
Group Energy Spot Separation (microns) Line
Raster Low Single 1.0 6 6
Raster Low Multiple 1.0 6 6
Raster High Single 1.9 11 9
Spiral Low Multiple 1.0 6 6
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Methods

• Fresh porcine eyes(n2 for each group)
• 30 kHz INTRALASE Femtosecond laser was used to
  cut cornea flap.
• Following the procedure, the donor tissue was
  immersed in fixative.
• Scanning Electron microscopy(SEM) was used to
  assess relative smoothness of tissue.

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Raster Low Multiple
Raster Low Single
Spiral Low Multiple
Raster High Single
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Results

• Raster Low Single pass appeared to have smoothest
  surface.
• Contradicts expected results however possible
  error introduced when multiple pass done in
  different directions.
• Observed that easier to lift flap with multiple
  pass than single.
• Overall raster smoother than spiral.

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Limitations

• Delay between fixating tissue and sending for SEM
  (environmental).
• Challenge interpreting SEM picture without bias.
• Sample size low.
• Femtosecond 30kH machine used here may make
  extrapolating results to other laser machine
  difficult.

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Conclusions

• Ideal to use human eyes in the future, using pig
  eyes may have introduced some error and
  difficulty in applying results.
• Possible use of software programs to quantify
  analysis of SEM photos.
• Principles applied here can hopefully bring us
  closer to achieving perfect visual outcome
  following DSAEK.

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Thank You

• References
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• Binder PS et al. Characterization of Submicrojule
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