In Vivo Evidence of Porcine Cornea Anisotropy Using Supersonic Shear Wave Imaging

PURPOSE. This work proposes shear wave elastography to quantify the elastic anisotropy of the cornea. METHODS. Experiments were conducted on enucleated porcine eyeballs and anesthetized swine. We used the supersonic shear wave imaging (SSI) method implemented on a dedicated 15-MHz rotating linear ultrasound array. This setup allows determining the shear wave speed variations for a set of radial propagation directions. RESULTS. All the results showed a local anisotropy with one main direction of maximal stiffness. The influence of pulsatility was observed in vivo, and electrocardiogram (ECG) gating was consequently performed for all anesthetized swine. On ex vivo corneas, n = 27 acquisitions were performed in the limbus region, where the collagen fibrils are reported to run tangentially to the sclera. A good match was shown between the direction of maximal stiffness and the expected direction of the collagen fibrils. CONCLUSIONS. This preliminary study demonstrates the potential of SSI for the assessment of corneal anisotropy in both ex vivo and in vivo conditions.