Noninvasive evaluation of corneal viscoelasticity based on displacement in response to acoustic radiation force

Noninvasive assessment of corneal mechanical properties in vivo will help to the understanding of the pathogenesis and early diagnosis of ectatic corneal disorders. This study presented a noninvasive method that assesses the corneal biomechanical properties by exciting the cornea with acoustic radiation force and monitoring its displacement using a dual-frequency confocal transducer. A 3.85-MHz pushing element was used to induce localized tissue displacement, and the displacement was detected by the 12.8-MHz detecting elements using pulse-echo methods. Under constant acoustic radiation force, 0the tissue displacement are directly correlated with tissue biomechanical properties, a set of parameters were extracted from local displacement waveform, including relaxation time constant (τ), relative elasticity (RE) and relative viscosity (RV). In order to obtain corneal samples with different mechanical properties, the fresh bovine eyes were performed by collagen cross-linking (CXL). The result indicated that the estimated τ in untreated corneas were statistically significantly different (p<;0.05) from those of treated corneas and the estimation of τ varied significantly with different degrees of CXL. It is possible to develop a non-invasive, effective and efficient method with high spatial resolution.