Long-term refraction and keratometry after penetrating keratoplasty for keratoconus

We looked for continued corneal ectasia after penetrating keratoplasty (PK) for keratoconus by measuring long-term changes in keratometry and refraction after final suture removal. The records of 587 patients who had had PK for keratoconus and who had attended a single center over a 7-year period were examined. For 184 eyes keratometry or refraction data were available from the first operated eye from the 6-month interval after final suture removal, and, in these patients, these readings were repeated as they continued to be seen for review. The changes in mean keratometry, spherical equivalent, and cylinder over the period of follow-up were then calculated, and these data were assessed by regression analysis. We found no significant change with time in the amount of cylinder when measured by either refraction or keratometry. There was a trend (p = 0.075) toward an increase in the mean keratometry with time, suggesting a gradual flattening of the cornea, and there was a clinically small, but statistically significant (p < 0.001), time-dependent increase in the residual myopia in the years after final suture removal. In conclusion, we found a wide range in the individual values for changes in keratometry or refraction in the years after suture removal following PK for keratoconus but no evidence overall to suggest continued corneal ectasia or a recurrence of keratoconus in these grafts.