Corneal thickness as a predictor of corneal transplant outcome

Abstract

Purpose: To assess corneal thickness (CT) and correlation with graft outcome after penetrating keratoplasty in the Cornea Donor Study.

Methods: A total of 887 subjects with a corneal transplant for a moderate-risk condition (principally Fuchs dystrophy or pseudophakic corneal edema) had postoperative CT measurements throughout a 5-year follow-up time. Relationships between baseline (recipient, donor, and operative) factors and CT were explored. Proportional hazards models were used to assess the association between CT and graft failure. Relationship between CT and cell density was assessed with a longitudinal repeated measures model and Spearman correlation estimates.

Results: Higher longitudinal CT measurements were associated with the following: diagnosis of pseudophakic or aphakic corneal edema (P < 0.001), intraocular pressure >25 mm Hg during the first postoperative month (P = 0.003), white (non-Hispanic) donor race (P = 0.002), and respiratory causes of donor death (P < 0.001). Among those without graft failure within the first postoperative year, the 5-year cumulative incidence (± 95% confidence interval) of graft failure was 5% ± 5% in those with a 1-year CT ≤ 500 μm, 5% ± 3% for CT 501 to 550 μm, 7% ± 4% for CT 551 to 600 μm, and 20% ± 11% for CT >600 μm. In a multivariate analysis, both 1-year CT and cell density were associated with subsequent graft failure (P = 0.002 and 0.009). CT increase was modestly associated with endothelial cell loss during follow-up (r = -0.29).

Conclusions: During the first 5 years after penetrating keratoplasty, CT can serve as a predictor of graft survival. However, CT is not a substitute for cell density measurement because both measures were independently predictive of graft failure.

Figure 1

Box Plot of Corneal Thickness Measurements (μm) over Study Follow up (N=887). Description: In the box plot, black dots indicate mean values; horizontal lines in the boxes, medians; and the bottom and top of the boxes, the 25th and 75th percentiles.

Figure 2

Median ECD and CT Values Over Time.

Figure 3

Boxplot of Corneal Thickness (μm) Over Time According to Graft Failure Status (N=887). Description: The decreasing trend over time in the graft failure group is likely a result of selective removal of failed grafts which tend to have higher CT values.

Figure 4

Kaplan-Meier Plot of Graft Failure According to 1 Year CT (N=621). Description: Kaplan-Meier plots and 5-year failure rates are calculated conditional on graft survival by year 1. Among 640 participants with 1 year CT measurement, 13 were censored and 6 experienced graft failure prior to year 1.