Morphology, Accuracy, and Histology of Corneal Flap Cuts Using a 200 kHz Femtosecond Laser

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Morphology, Accuracy, and Histology of Corneal
Flap Cuts Using a 200 kHz Femtosecond Laser
R. Khoramnia C.P. Lohmann J. Salgado C.
Winkler von Mohrenfels
ASCRS 2010

• Augenklinik, Klinikum rechts der Isar, Technische
  Universität München, Munich, Germany
• All authors have no financial interest in the
  subject matter of this poster.
• The laser system used is not FDA approved and
  does not yet have a CE mark.

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Purpose

• - LASIK requires precise corneal flap cutting.
• Especially the creation of thin flaps has
  recently gained importance for Sub-Bowman
  keratomileusis (SBK), which requires precise
  cutting.
• There is a tendency towards faster femtosecond
  lasers that produce flaps more quickly.

We analyzed flaps created with a prototype 200
kHz femtosecond laser (UltraFlap WaveLight AG,
Erlangen, Germany) concerning their cut accuracy,
morphology, and histology.
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Material and methods
Preparation 36 fresh porcine eyes Epithelial
abrasion
Surgery Femtosecond laser flap cutting using the
200 kHz femtosecond laser -gt Three thickness
groups (100 µm, 130 µm, or 180 µm) -gt Flap
diameters were varied ranging from 8.0 to 9.5 mm
Examination 1.) Flap diameters were measured with
a sliding caliper. 2.) Flap thickness was
measured with a micrometer gauge (Extramess
2000 Mahr, Esslingen, Germany). Accuracy of
this device 0.3 µm 3.) Histologic examination
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Results Flap thickness
Box-and-whisker plot

• Accuracy - Statistical analysis
• Significant difference between the 130- and
  180-µm group (Mann-Whitney-U test p lt 0.05)
• All other comparisons No significant
  differences (Mann-Whitney-U test p gt 0.05).

Mean values 96.337.45
134.674.96 174.599.35 µm
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Results Flap diameter
Box-and-whisker plot

• Accuracy - Statistical analysis
• The deviation between measured and attempted
  diameters was not significantly different between
  the four diameters (Kruskal-Wallis test p gt
  0.05).

Mean values 8.030.15 8.030.15
9.090.10 9.540.15 mm mm
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Results Histological examination

• (A) A 180-µm flap in the region of the side cut.
  
• (B) Stromal bed in the region of the side cut
  (flap thickness 100 µm).
• A 130-µm flap and the stromal bed.
• HE staining original magnification, x20.

Histology showed a smooth cut with very little to
almost no changes in the corneal structure.
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Conclusions

• Flap creation was performed easily without any
  complications.
• Morphology and accuracy of the cuts were very
  reliable and precise.
• Histology showed a smooth cut with very little to
  almost no changes in the corneal structure.
• -gt Therefore, the 200 kHz femtosecond laser
  seems to be a promising new device in refractive
  surgery.

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CONTACT
Klinik und Poliklinik für Augenheilkunde
Klinik und Poliklinik für Augenheilkunde am
Klinikum rechts der Isar Ismaninger Str.
22 81675 Munich GERMANY SECRETARIAT Tel. 49 89
41 40-23 20 Fax [phone] E-Mail
augenklinik_at_lrz.tum.de Internet
www.augenklinik-mri.de
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