THE EFFECT OF TREPHINATION ON CORNEAL TOPOGRAPHY

BACKGROUND AND OBJECTIVE: A prospective study was performed to assess the effect of trephination on corneal curvature. MATERIALS AND METHODS : Thirty-seven fresh porcine globes with intact corneal epithelium wer e used. Radius of curvature, central dioptric power, and powers and ax es of the steepest and flattest meridians were obtained using a vertic ally mounted computerized videokeratography unit. Following 8-mm vacuu m 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 curva ture (mm) increased from 8.68 +/- 0.79 to 10.46 +/- 3.24 (P = .005), t he central dioptric power (D) decreased from 33.36 +/- 3.84 to 36.31 /- 10.15 (P = .08), and the total corneal asphericity (D) increased fr om 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 foll owing trephination. CONCLUSION: Trephination leads to significant corn eal flattening and increased asphericity. Corneal topography can be us ed successfully as a research tool for whole globes and trephined butt ons.