Effect of glucose on the stress-strain behavior of ex-vivo rabbit cornea

The biomechanical changes in rabbit cornea preserved in storage media with different glucose concentrations are experimentally assessed. Two groups of eight fresh rabbit corneas were preserved for 10 days in storage medium Optisol-GS with glucose concentrations of 14 and 28 mM, respectively. Eight additional corneas preserved, glucose-free, in the same medium served as the control group. All specimens were tested under inflation conditions up to 45 mmHg posterior pressure, and the pressure-deformation data obtained experimentally were analyzed using shell theory to derive the stress-strain behavior. Comparisons were held between the three specimen groups in order to determine the effect of glucose concentration on corneal biomechanical behavior and thickness. After storage, the mean central corneal thickness in the control, low-glucose and high-glucose groups underwent statistically significant increases of 38.7 ± 11.3%, 45.4 ± 7.6% and 50.6 ± 8.6%, respectively. The corneas also demonstrated consistent stiffness increases with higher glucose concentrations. The tangent modulus values determined at different pressure levels between 10 and 40 mmHg underwent statistically significant increases with glucose level (P < 0.05). Compared to the control group, other specimens had higher tangent modulus by 17-20% on average with low glucose and 30-37% with high-glucose concentration. The results of the study indicate that the influence of the high-glucose level commonly experienced in diabetes on the biomechanical stiffness of the cornea should be considered in clinical management and in understanding corneal ectasia, glaucoma and the response to refractive surgery.