title: Smoothness of ablation on acrylic by four different excimer lasers.
abstract: OBJECTIVE
  There are many different excimer laser devices available for photoablative refractive surgery. Smoothness of ablation may vary with different excimer lasers systems.
  
  
  METHODS
  Ablations were performed on polymethylmethacrylate (PMMA) plates of 8 x 4 x 0.5 cm, with four different excimer lasers: VISX-Star, Coherent Schwind Keratom I/II, Chiron Technolas Keracor 117C (Plano Scan), and the Nidek EC-5000, to determine and compare the homogeneity and smoothness of the surface. Ten -3.00 D samples, ten -6.00 D samples, and ten -9.00 D samples were ablated with each laser. The PMMA discs were examined with optical microscopy, documented by photographs, and each sample was measured quantitatively using a Hommel-Werkel rugosimeter. We used the same PMMA material throughout.
  
  
  RESULTS
  Statistically significant differences in smoothness were found between the Chiron Technolas 117C and the VISX-Star, Nidek and VISX-Star, and Coherent Schwind and VISX-Star in the homogeneities achieved by ablating -3.00 D. Ablations of -6.00 D resulted in homogeneities that were statistically significantly different: Chiron Technolas 117C with the other three devices, the Nidek EC-5000 with the VISX-Star, and the Coherent-Schwind with the VISX-Star. In the ablations for -9.00 D, statistically significant differences in homogeneity were found between the Chiron Technolas 117C and Nidek, between the Chiron and VISX-Star, between the Coherent Schwind and VISX-Star, and between the Nidek and VISX-Star. The laser with the scanning spot system was smoother.
  
  
  CONCLUSIONS
  Scanning spot technology produced smooth ablations even up to -9.00 D.
authors.affiliation: Cornea Department, Hospital de Clínicas Jose de San Martin, Buenos Aires, Argentina.
authors.forename: C
authors.initials: C
authors.lastname: Argento
authors.forename: G
authors.initials: G
authors.lastname: Valenzuela
authors.forename: H
authors.initials: H
authors.lastname: Huck
authors.forename: G
authors.initials: G
authors.lastname: Cremona
authors.forename: M J
authors.initials: MJ
authors.lastname: Cosentino
authors.forename: M F
authors.initials: MF
authors.lastname: Gale
mesh_terms: D054018:Lasers, Excimer; D008953:Models, Anatomic; D018903:Photorefractive Keratectomy / Q000379:methods; D019904:Polymethyl Methacrylate; D013499:Surface Properties
chemical_list: D019904:Polymethyl Methacrylate