Klinik und Poliklinik für Augenheilkunde

Morphology, Accuracy, and Histology of Corneal Flap Cuts Using a

200 kHz Femtosecond Laser

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.

ASCRS 2010

R. Khoramnia C.P. Lohmann

J. Salgado C. Winkler von Mohrenfels

Klinik und Poliklinik für Augenheilkunde

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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.

Klinik und Poliklinik für Augenheilkunde

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Material and methodsPreparation

36 fresh porcine eyes: Epithelial abrasion

Surgery

Femtosecond laser flap cutting using the 200 kHz femtosecond laser

-> Three thickness groups (100 µm, 130 µm, or 180 µm)

-> 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

Klinik und Poliklinik für Augenheilkunde

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Results: Flap thickness

Accuracy - Statistical analysis:

Significant difference between the 130- and 180-μm group (Mann-Whitney-U test; p < 0.05)

All other comparisons: No significant differences (Mann-Whitney-U test; p > 0.05).

Box-and-whisker plot

Mean values: 96.33±7.45 134.67±4.96 174.59±9.35 [µm]

Klinik und Poliklinik für Augenheilkunde

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Results: Flap diameter

Accuracy - Statistical analysis:

The deviation between measured and attempted diameters was not significantly different between the four diameters (Kruskal-Wallis test; p > 0.05).

Box-and-whisker plot

Mean values: 8.03±0.15 8.03±0.15 9.09±0.10 9.54±0.15 mm [mm]

Klinik und Poliklinik für Augenheilkunde

Results: Histological examination

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

(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).

(C) A 130-µm flap and the stromal bed.

H&E staining; original

magnification, x20.

Klinik und Poliklinik für Augenheilkunde

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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.

-> Therefore, the 200 kHz femtosecond laser seems to be a promising new device in refractive surgery.

Klinik und Poliklinik für Augenheilkunde

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CONTACT

Klinik und Poliklinik für Augenheilkunde

Klinik und Poliklinik für Augenheilkundeam Klinikum rechts der Isar

Ismaninger Str. 2281675 MunichGERMANY

SECRETARIATTel. + 49 89 41 40-23 20Fax + 49 89 41 40-48 58

E-Mail: augenklinik@lrz.tum.deInternet: www.augenklinik-mri.de