Comparative Analysis of Two Measurement Modalities for Ex Vivo Analysis of Corneal Stiffness in Porcine Corneas

This study compared two widely used biomechanical testing modalities—uniaxial tensile testing and AFM nanoindentation—to characterize stiffness changes in porcine corneas following corneal crosslinking (CXL). Sixty-two eyes were assigned to control, Dresden-protocol CXL (CXL3), or accelerated CXL (CXL9) groups, then evaluated using both modalities on paired corneal samples. Uniaxial tensile testing demonstrated a clear stiffening response, with CXL3 producing the largest increase (≈1.96-fold increase in Young’s modulus at 10% strain), followed by CXL9 (≈1.48-fold). AFM nanoindentation detected similar directional trends, with localized stiffness increases of 16–28%, though group differences were not statistically significant due to spatial heterogeneity at the micrometer scale. The findings highlight how tensile testing captures global stiffening across the entire tissue strip, while nanoindentation reveals position-dependent stromal variations. Together, the modalities offer complementary insights into the biomechanical effects of different CXL protocols.