title: [Correlation between semi-quantitative classification of corneal topography and the coefficient of Fourier transformation after non-mechanical perforating keratoplasty].
abstract: BACKGROUND
  Semiquantitative classification of corneal topography after penetrating keratoplasty has the potential for focusing information about the areal dioptric power of the cornea. The purpose of this study was to objectify the procedure of manual semiquantitative classification using a Fourier transform of corneal topography power data and to correlate both methods.
  
  
  METHODS
  Fifty patients each (30 keratoconus, 20 Fuchs dystrophy) underwent nonmechanical trephination (excimer laser MEL60, Aesculap-Meditec, Jena) in penetrating keratoplasty. All procedures (7.5-mm trephination diameter in Fuchs, 8.0 mm in keratoconus, double-running 10-0 nylon suture) were done by one surgeon. Pre-, intra- and postoperative treatment were identical. At the follow-up examinations, the keratometric astigmatism, qualitative and quantitative criteria of the automatic videokeratography, visual acuity and refraction were assessed. Corneal topography was classified both manually and based on Fourier coefficients.
  
  
  RESULTS
  After a mean follow-up of 24 +/- 5 months, keratometric net astigmatism was 3.0 and 2.7 D with keratoconus and Fuchs dystrophy. Corneal topography analysis showed a higher orthogonality of the bow-tie shape and less asymmetry between opposite hemimeridians with increasing follow-up after keratoplasty. The semiquantitative classification showed a statistically significant correlation with the classification based on Fourier coefficients, especially with higher astigmatism and after suture removal (P = 0.04/0.01 before/after suture removal).
  
  
  CONCLUSIONS
  After nonmechanical trephination, the semiquantitative classification of corneal topography can be synthetized using Fourier analysis of corneal dioptric power data. In the future, this method may be favored for prediction of potential best-corrected visual acuity after penetrating keratoplasty.
authors.affiliation: Augenklinik mit Poliklinik, Universität Erlangen-Nürnberg.
authors.forename: A
authors.initials: A
authors.lastname: Langenbucher
authors.forename: B
authors.initials: B
authors.lastname: Seitz
authors.forename: M M
authors.initials: MM
authors.lastname: Kus
authors.forename: G O
authors.initials: GO
authors.lastname: Naumann
mesh_terms: D000328:Adult; D000368:Aged; D001251:Astigmatism / Q000175:diagnosis; D019781:Corneal Topography / Q000706:statistics & numerical data*; D005260:Female; D005583:Fourier Analysis; D005642:Fuchs' Endothelial Dystrophy / Q000601:surgery*; D006801:Humans; D007640:Keratoconus / Q000601:surgery*; D015948:Keratoplasty, Penetrating; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000175:diagnosis*; D012029:Refraction, Ocular
vernacular_title: Korrelation zwischen semiquantitativer Klassifizierung der Hornhauttopographie und den Koeffizienten der Fourier-Zerlegung nach nichtmechanischer perforierender Keratoplastik.