title: Comparison of different excimer laser ablation frequencies (50, 200, and 500 Hz).
abstract: OBJECTIVE
  The aim of this study was to compare the influence of different excimer laser (193 nm) ablation frequencies (50, 200, and 500 Hz) on porcine cornea.
  
  
  METHODS
  For this study, fresh porcine cadaver eyes were obtained from the butcher. PRK and LASIK were performed using a WaveLight Concept System 500 excimer laser. Various repetition rates (50, 200, and 500 Hz) and intended corrections (between -3 and -9 D) were used. Corneal endothelium was investigated pre- and post-operatively with the endothelial cell microscope EM 1000 Tomey. Post-operatively, the corneas were embedded for light microscopic (HE, Picrosirius Red) and electron microscopic evaluation.
  
  
  RESULTS
  The mean pre-operative cell count was 2,953 (SD 149) and the mean post-operative cell count was 2,974 (SD 156). There was no difference between the pre- and post-operative cell count and the different ablation frequencies. The distribution of collagen fibers and keratocytes was comparable in all different ablation frequencies. Also, the ultrastructural evaluation of keratocytes and fibers, assessed with transmission electron microscopy, was equal in all three different ablation frequencies.
  
  
  CONCLUSIONS
  The endothelial cell density and structural and ultra structural evaluation of the different ablation frequencies (50, 200, 500 Hz) showed no specific side-effects that could be associated with higher repetition rates. The quality of the ablation was comparable in all three different laser ablation frequencies. The 500-Hz excimer laser can provide the same ablation quality as slower platforms, but can also offer the advantage of requiring less treatment time than other laser platforms with lower repetition rates.
authors: Klinik und Poliklinik für Augenheilkunde, Klinikum rechts der Isar, Munich, Germany. christoph.wvm@web.de
authors: C
authors: C
authors: Winkler von Mohrenfels
authors: R
authors: R
authors: Khoramnia
authors: C-P
authors: CP
authors: Lohmann
mesh_terms: D000818:Animals; D002452:Cell Count; D003094:Collagen / Q000378:metabolism; D003315:Cornea / Q000378:metabolism / Q000601:surgery* / Q000648:ultrastructure; D004728:Endothelium, Corneal / Q000473:pathology; D005347:Fibroblasts / Q000473:pathology; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D008858:Microscopy, Phase-Contrast; D018903:Photorefractive Keratectomy / Q000379:methods*; D013552:Swine
chemical_list: D003094:Collagen