title: The effect of trephination on corneal topography.
abstract: OBJECTIVE
  A prospective study was performed to assess the effect of trephination on corneal curvature.
  
  
  METHODS
  Thirty-seven fresh porcine globes with intact corneal epithelium were used. Radius of curvature, central dioptric power, and powers and axes of the steepest and flattest meridians were obtained using a vertically mounted computerized videokeratography unit. Following 8-mm vacuum trephination of the central donor corneas, the said parameters were reassessed on the resultant buttons. No globes with epithelial defects were included in the study.
  
  
  RESULTS
  The mean corneal radius of curvature (mm) increased from 8.68 +/- 0.79 to 10.46 +/- 3.24 (P = .005), the central dioptric power (D) decreased from 39.36 +/- 3.84 to 36.31 +/- 10.15 (P = .08), and the total corneal asphericity (D) increased from 5.03 +/- 2.99 to 7.47 +/- 3.42 (P = .0001). No significant changes in the axes of the steepest and the flattest meridians were noted following trephination.
  
  
  CONCLUSIONS
  Trephination leads to significant corneal flattening and increased asphericity. Corneal topography can be used successfully as a research tool for whole globes and trephined buttons.
authors: New England Eye Center, New England Medical Center, Tufts University School of Medicine, Boston, MA 02111, USA.
authors: D S
authors: DS
authors: Greenfield
authors: S Q
authors: SQ
authors: Jivanjee
authors: M B
authors: MB
authors: Raizman
mesh_terms: D000818:Animals; D001251:Astigmatism / Q000209:etiology / Q000473:pathology*; D003315:Cornea / Q000473:pathology*; D016039:Corneal Transplantation / Q000009:adverse effects*; D007091:Image Processing, Computer-Assisted; D011446:Prospective Studies; D013552:Swine