Influence of High-Dose Cortisol on the Biomechanics of Incubated Porcine Corneal Strips

Abstract

To investigate the change in biomechanical properties of the cornea induced by high-dose hydrocortisone. The influence of hydrocortisone was investigated in 12 fresh porcine corneas incubated in culture medium of 2.5 muM of hydrocortisone for 7 days. Twelve additional porcine corneas incubated in culture medium without hydrocortisone for the same time served as the control group. Strips of cornea were cut and the stress-strain relationship was measured in a biomaterial tester. Young's modulus was calculated. After incubation, the thickness of the cornea was 1120+/-130 mum in the control group and 1320+/-90 mum in the hydrocortisone group. The hydrocortisone-treated corneas were 18% thicker compared to the control corneas. However, the difference in the biomechanical stress value at 10% strain was significantly larger. In the control group, the stress value measured 122+/-40 kPa, and in the hydrocortisone group, it measured 77+/-19 kPa (P=.003), representing a reduction of the corneal stiffness by 37% due to hydrocortisone treatment. Young's modulus was reduced by 42.8% from 2.90+/-1.10 MPa in the control group to 1.66+/-0.49 in the hydrocortisone group. Hydrocortisone is a modulating factor of the biomechanical properties of the cornea. The significance of the cortisol status of the patient and its influence on the biomechanical stability of the cornea should be considered in the development of keratectasia in keratoconus or after refractive surgery.