Diabetes mellitus affects biomechanical properties of the optic nerve head in the rat.

BACKGROUND

To investigate the effect of diabetes on the biomechanical behavior of the optic nerve head (ONH) and the peripapillary sclera (ppSc) in streptozocine-induced diabetic rats.

METHODS

Diabetes mellitus was induced in 20 Wistar rats using streptozocine. Twenty-five nondiabetic rats served as controls. Eyes were enucleated after 12 weeks and 2 strips of one eye were prepared containing ONH or ppSc. The stress-strain relation was measured in the stress range of 0.05-10 MPa using a biomaterial tester.

RESULTS

At 5% strain the stress of the ONH in diabetic rats was 897±295 kPa and in the control group it was 671±246 kPa; there was a significant difference between both groups (p=0.011). The stress of the diabetic ppSc (574±185 kPa) increased compared to that of the nondiabetic ppSc (477±171 kPa), but this did not reach statistical significance (p=0.174). The calculated tangent modulus at 5% strain was 11.79 MPa in the diabetic ONH and 8.77 MPa in the nondiabetic ONH; there was a significant difference between both groups (p=0.006). The calculated tangent modulus at 5% strain was 7.17 MPa in the diabetic ppSc and 6.12 MPa in the nondiabetic ppSc, without a statistically significant difference (p=0.09).

CONCLUSION

In contrast to the ppSc, the ONH of diabetic rats showed a significant increase in stiffness compared to nondiabetic rats, which might be explained by nonenzymatic collagen cross-linking mediated by advanced glycation end products due to high blood glucose levels in diabetes. Further studies are needed to investigate if these biomechanical changes represent a detrimental risk factor for intraocular pressure regulation in diabetic glaucoma patients.