[Reproducibility of femtosecond laser incisions for posterior lamellar keratoplasty in vitro].
OBJECTIVE
In the last decade surgeons have tried to use posterior lamellar keratoplasty (PLAK) in a way that maintains the biomechanical stability of the intact cornea. Femtosecond lasers can be used to cut a lenticle out of the posterior part of the stroma. The purpose of this study was to assess the reproducibility of the generated lenticles.


METHODS
The FEMTEC-Laser (20/10 Perfect Vision, Heidelberg, Germany) was used to perform posterior lamellar dissections. The goal was to assess the real thickness of the graft in comparison to the intended thickness predefined with the laser. The histological preparations were viewed using light microscopy (Olympus microscope). Main outcome measures included difference of intended versus real distance of the horizontal plane from Bowman's layer and quantification of the created bubbles.


RESULTS
The intended distance was reached with a precision of 115-160 µm and was constant over the whole length of the lenticle depending on the depth of the laser action. The number and size of the generated bubbles was equal in the different layers. At least one zone of stromal condensation could be found in 88.9% of the corneas and 63% of the corneas showed a partial perforation or minimal lesions of Descemet's membrane. The distance of the two closest bubbles to Descemet's membrane increased in thinner lenticles, i.e. a greater distance from Bowman's layer. No damage occurred due to compression or heat.


CONCLUSIONS
As the laser generates a reproducible number of bubbles of the same size, precise incisions can be achieved. Thus the femtosecond laser proved to be an accurate tool for PLAK. In the majority of cases a lesion of Descemet's membrane could be found which seems to make the removal of the lenticles easier. A disadvantage is a decreasing probability of a lesion of Descemet's membrane as well as the decreasing precision in thinner lenticles.
Augenklinik mit Poliklinik, Universität Erlangen-Nürnberg, Erlangen.
S
S
Harlfinger
A
A
Langenbucher
C
C
Hofmann-Rummelt
B
B
Seitz
D048988:Corneal Surgery, Laser / Q000295:instrumentation* / Q000379:methods*; D016039:Corneal Transplantation / Q000295:instrumentation* / Q000379:methods*; D003886:Descemet Membrane / Q000473:pathology* / Q000601:surgery*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity