Corneal endothelium and postoperative outcomes 15 years after penetrating keratoplasty

Abstract

Purpose: To determine changes in the central endothelium and thickness of grafted corneas, and the cumulative probability of developing glaucoma, graft rejection, and graft failure 15 years after penetrating keratoplasty.

Methods: In a longitudinal cohort study of 500 consecutive penetrating keratoplasties by one surgeon, regrafted eyes, fellow eyes of bilateral cases, and patients not granting research authorization were excluded, leaving 388 grafts for analysis. At intervals after surgery, we photographed the endothelium and measured corneal thickness by using specular microscopy. The presence of glaucoma, graft rejection, and graft failure was recorded.

Results: The 67 patients examined at 15 years represented 30% of the available clear grafts (107 patients had died, 76 grafts had failed). Endothelial cell loss from preoperative donor levels was 71 +/- 12% (mean +/- SD, n = 67), endothelial cell density was 872 +/- 348 cells/mm2, and corneal thickness was 0.59 +/- 0.06 mm. Endothelial cell density was unchanged between 10 and 15 years (minimum detectable difference was 96 cells/mm2, alpha = .05, beta = .20, n = 54), whereas corneal thickness increased (P = .001, n = 55). The mean annual rate of endothelial cell loss from 10 to 15 years after surgery was 0.2 +/- 5.7% (n = 54). The cumulative probability of developing glaucoma, graft rejection, or graft failure was 20%, 23%, and 28%, respectively, and six of the eight graft failures after 10 years resulted from late endothelial failure.

Conclusions: From 10 to 15 years after penetrating keratoplasty, the annual rate of endothelial cell loss was similar to that of normal corneas, corneal thickness increased, and late endothelial failure was the major cause of graft failure.

Figure 1

Endothelial cell data fitted to a biexponential decay model for all available data through 15 years. The dotted lines represent the 95% confidence interval. The coefficients are shown with their standard error (se) and corresponding P value. The fast half-life was 8.2 months, and the slow half-life was 229.5 months. The residual standard deviation was 123.9 cells/mm². The rate of cell loss represented by the slow exponential was 3.6% per year.

Figure 2

Endothelial cell data fitted to a biexponential decay model for patients who attended every follow-up examination and who had no episode of rejection or surgery that could affect the endothelium (n = 27). The dotted lines represent the 95% confidence interval. The coefficients are shown with their standard error (se) and corresponding P value. The fast half-life was 13.0 months, and the slow half-life was 266.5 months. The residual standard deviation was 206.0 cells/mm². The rate of cell loss represented by the slow exponential was 3.1% per year.

Figure 3

Cumulative probability of developing glaucoma by preoperative diagnosis. The overall probability of developing glaucoma at 15 years was 20%. Corneas transplanted for a preoperative diagnosis of keratoconus had a significantly lower cumulative probability of developing glaucoma than corneas transplanted for aphakic or pseudophakic corneal edema (P < .001, Bonferroni-adjusted for 10 comparisons), and corneas transplanted for Fuchs’ dystrophy had a lower cumulative probability of developing glaucoma than corneas transplanted for pseudophakic corneal edema (P < .001, Bonferroni-adjusted for 10 comparisons).

Figure 4

Cumulative probability of developing graft rejection by preoperative diagnosis. The overall probability of developing graft rejection at 15 years was 23%. The cumulative probability of developing graft rejection did not differ among preoperative diagnoses (P > .05, Bonferroni-adjusted for 10 comparisons).

Figure 5

Cumulative probability of developing overall graft failure by preoperative diagnosis. The overall probability of developing graft failure at 15 years was 28%. Corneas transplanted for keratoconus had a lower cumulative probability of failing compared to corneas transplanted for Fuchs’ dystrophy (P = .05, Bonferroni-adjusted for 10 comparisons) or for aphakic corneal edema (P = .006, Bonferroni-adjusted for 10 comparisons).

Figure 6

Cumulative probability of developing late endothelial failure by preoperative diagnosis. The overall probability of developing late endothelial failure at 15 years was 12%. Corneas transplanted for keratoconus had a lower cumulative probability of developing late endothelial failure compared to corneas transplanted for Fuchs’ dystrophy (P = .03, Bonferroni-adjusted for 10 comparisons).