Glucose Permeability of Human, Bovine, and Porcine Corneas in vitro

Purpose: To measure glucose flux across human, bovine, and porcine corneas and to determine the diffusion coefficient of each type of cornea. Methods: Diffusion of glucose across human (n = 8), bovine (n = 7), and pig corneas (n = 8) was measured using a modified blind well chamber apparatus (Boyden chamber). Dialysis membranes (n = 7) and nonporous Mylar membranes (n = 7) were used as positive and negative controls, respectively. Glucose concentrations were measured at 30-min intervals with a commercially available glucose meter. Results: The diffusion of glucose through corneas in vitro was calculated by a simple Fickian diffusion model. The diffusion coefficient of glucose is highest for the human cornea (D_HC = 3.0 ± 0.2 × 10^–6 cm²/s) followed by porcine corneas (D_PC = 1.8 ± 0.6 × 10^–6 cm²/s) and bovine corneas (D_BC = 1.6 ± 0.1 × 10^–6 cm²/s) (p < 0.05). The diffusion coefficients of all tested corneas were significantly higher (p < 0.05) than that of dialysis membrane (D_DM = 3.4 ± 0.2 × 10^–7 cm²/s). Conclusion: The glucose diffusion coefficients of human, bovine, and porcine corneas are on the order of 10^–6. Human corneas have higher permeability to glucose than either porcine or bovine corneas.