Effects of corneal preservation on the mechanical response of porcine corneas measured by nano-indentation

Although corneal biomechanics plays an important role in ophthalmology, its characterization remains limited due to tissue availability. This problem is particularly critical when studying specific pathologic conditions such as keratoconus. A preservation method that maintains the mechanical response of the tissue over time allows the collection, transport, and storage of tissue samples from different, distant clinical sites and increases the number of samples available for testing. Therefore, the aim of this study was to quantify the change in mechanical response of porcine corneas after 6 days of storage either at −20°C or in standard culture medium. The viscoelastic response of porcine corneas was measured at different loading rates by nano-indentation. While the loading rate had a significant effect on the mechanical response (p < .0001), the results showed that the mechanical response were not altered by any of the preservation methods (p > .270). However, the standard deviation was up to 4.9 times larger when the samples were stored in the culture medium compared to the fresh and frozen samples. In addition, storage in culture medium resulted in significant swelling (+38%). In conclusion, although both preservation techniques provide equivalent mechanical response measured by nano-indentation, freezing the samples prevents swelling and provides more stable measurements.