The effect of estrogen and progesterone on porcine corneal biomechanical properties

Purpose To determine the effect of the hormones estrogen and progesterone on the biomechanical properties of porcine corneas. Methods Thirty fresh porcine corneas were acquired from an abattoir. The corneas were equally divided into three groups. Groups were incubated for 1 week in Eusol-C solution containing supra-physiologic concentrations of estrogen, progesterone, or control (no added hormone). After incubation, the central corneal thickness (CCT) of each cornea was measured using an electronic caliper, and then the corneas were cut into strips. The strips were then clamped in the pneumatic jaws of a computer-controlled biomaterial tester (Instron 4502, USA) and stretched at a constant rate of 1 mm/min until tissue rupture while constantly recording the stress and strain of the tissue. Stress-strain curves were plotted and Young's modulus was calculated for each corneal strip. Results Average corneal thickness was 873.5 +/- 143.1 mu m for the control group, 928.0 +/- 97.7 mu m for the estrogen group, and 922.0 +/- 116.7 mu m for the progesterone group (data presented as mean +/- SD). There was no statistically significant difference between the groups regarding the CCT (p = 0.89). The average Young's modulus was 17.00 +/- 3.46 MPa for the control group, 16.95 +/- 6.83 MPa for the progesterone group, and 12.33 +/- 3.24 MPa for the estrogen group. The difference between the control and estrogen groups was statistically significant (p = 0.018) while the difference between the control and progesterone groups was not (p = 0.72). Conclusion Estrogen has a relaxing effect on the porcine cornea, resulting in reduced stiffness of the tissue. Progesterone has no significant effect on the biomechanical properties of porcine corneas. Estrogen and progesterone do not significantly affect CCT.