Predictive donor factors for chronic endothelial cell loss after nonmechanical penetrating keratoplasty in a regression model

Abstract

Purpose: To assess the diagnosis-based impact of donor parameters and trephination diameter as predictive factors on corneal endothelial cell density with an exponential regression model after nonmechanical penetrating keratoplasty (PK).

Methods: Six hundred thirty-one eyes [291 keratoconus (group I, trephination diameter 8.0 mm); 202 Fuchs' dystrophies (group II, trephination diameter 7.5 mm)-84 PK only (IIa) and 118 triple procedures (IIb); and 138 pseudophakic bullous keratopathies (group III, trephination diameter 6.5-8.0 mm)] were included in this retrospective study. The time course of the endothelial cell density (specular microscope EM 1100, Tomey, Erlangen) after PK was assessed. Endothelial cell density was analyzed in a longitudinal manner considering at least three valid postoperative cell counts (follow-up 29+/-17 months) with an exponential regression model (minimizing the residuum between observed and predicted endothelial cell count). The following potentially predictive parameters were assessed: donor age (DA), post-mortem time (PM), storage time (ST) and trephination diameter (group III).

Results: In the exponential regression model endothelial cell count decreased in I/II/III by 3.1+/-24.2% / 12.6+/-20.2% (IIa: 8.9+/-17.3%, IIb: 14.8+/-22.0%) / 18.7+/-27.3% annually. PM ( P=0.16 / P=0.10 / P=0.25) and DA ( P=0.20, / P=0.12 / P=0.16) did not correlate with the cell loss, but ST ( P=0.04 / P=0.04 / P=0.02) showed a mild correlation, especially in short-term-stored corneas. In group III the trephination diameter ( P=0.01) correlated inversely with the cell loss. Between short-term-preserved and organ-cultured donor corneas there was no statistically significant difference in the cell loss in any group.

Conclusions: The post-mortem time and the donor age is not associated with a chronic endothelial cell loss after keratoplasty, whereas a long storage time may exaggerate the endothelial cell loss. Between short-term-preserved and organ-cultured donor corneas there was no difference in the time gradient. In bullous keratopathy patients a larger trephination size reduces the chronic endothelial cell loss.