title: Irregularity of the posterior corneal surface during applanation using a curved femtosecond laser interface and microkeratome cutting head.
abstract: OBJECTIVE
  To evaluate the irregularity of the posterior corneal surface and intrastromal dissection during the preparation of donor tissue for Descemet stripping automated endothelial keratoplasty (DSAEK) using a curved interface femtosecond laser and microkeratome.
  
  
  METHODS
  Sixteen human donor corneas unsuitable for transplantation were divided into two groups: a femtosecond (FS) laser group (n=7) using the VisuMax femtosecond laser (Carl Zeiss Meditec) and a microkeratome group (n=9) using the Amadeus II microkeratome (Ziemer Ophthalmic Group). The corneas were fixed on artificial anterior chambers. Horizontal cross-sections were obtained using spectral-domain optical coherence tomography prior to applanation, during applanation, as well as during and after intrastromal dissection at 450-μm corneal depth. The posterior surface and the dissection line were evaluated for irregularity by fitting a second-order polynomial curve using regression analysis and obtaining the root-mean-square error (RMSE). Groups were compared using analysis of variance.
  
  
  RESULTS
  The RMSE of the posterior surface prior to applanation was 9.7 ± 3.1 μm in the FS laser group and 10.2 ± 2.3 μm in the microkeratome group. The RMSE increased to 50.7 ± 9.4 μm and 20.9 ± 6.1 μm during applanation and decreased again to 10.6 ± 1.4 μm and 8.1 ± 1.8 μm after applanation in the FS laser and microkeratome groups, respectively. The RMSE of the intrastromal cut was 19.5 ± 5.7 μm in the FS laser group and 7.7 ± 3.0 μm in the microkeratome group (P<.001).
  
  
  CONCLUSIONS
  Our results show significantly greater irregularity with the curved interface femtosecond laser-assisted cleavage compared to microkeratome-assisted corneal dissection, possibly due to applanation-derived deformation of the posterior cornea.
authors.affiliation: University Medical Center of the Johannes Gutenberg University Mainz, Department of Ophthalmology, Germany. jan.vetter@unimedizin-mainz.de
authors.forename: Jan M
authors.initials: JM
authors.lastname: Vetter
authors.forename: Carsten
authors.initials: C
authors.lastname: Holtz
authors.forename: Urs
authors.initials: U
authors.lastname: Vossmerbaeumer
authors.forename: Norbert
authors.initials: N
authors.lastname: Pfeiffer
mesh_terms: D000369:Aged, 80 and over; D003319:Corneal Stroma / Q000473:pathology* / Q000601:surgery*; D057111:Descemet Stripping Endothelial Keratoplasty / Q000295:instrumentation*; D004728:Endothelium, Corneal / Q000473:pathology*; D006801:Humans; D054018:Lasers, Excimer / Q000627:therapeutic use*; D013499:Surface Properties; D014019:Tissue Donors; D041623:Tomography, Optical Coherence