Topography of corneal grafts before and after penetrating keratoplasty

Abstract

Purpose: Refractive error after penetrating keratoplasty is a major clinical problem. The purpose of the present study was to investigate whether the topography of the donor cornea influence the topography of the graft after transplantation. Methods: Twenty-five donor corneas were measured with a video-keratograph (TMS-1): in situ and before and after organ culture. Clinical video-keratographic images of the transplanted grafts were subsequently obtained one week, 1, 3, 6, 12, and 24 months after surgery. The central spherical equivalent power and corresponding regular and irregular astigmatic powers were computed. Results: A statistically significant correlation between spherical equivalent central donor power and spherical equivalent central graft power after keratoplasty was found at all times up to two years after surgery. Only 13-50% of the variation in post-keratoplasty spherical graft power could, however, be explained by the donor graft power. Corresponding 95% confidence limits for prediction of post-keratoplasty power from donor graft power were approximately ± 6.5 diopters. Post-keratoplasty regular or irregular corneal astigmatism did not correlate with astigmatism in the donor graft. Conclusion: Corneal donor graft spherical equivalent power does influence the spherical equivalent corneal power after keratoplasty, especially during the first months after surgery. The dependency is, however, not very strong and until other determinants of post-keratoplasty corneal shape are known and controllable, 'power-typing' of donor corneas appears to be of limited clinical use.