Shear wave elastography (SWE) for the measurement of lens elasticity in the context of monitoring a presbyopia treatment by ultrasonic cavitation

Abstract

Presbyopia is a progressive loss of accommodation capacity due to a rigidification of the lens. In order to prove the efficiency of ultrasonic cavitation to soften the lens, curvilinear SWE has been developed. It is a method to measure stiffness based on the tracking of surface waves on the outer layer of lens. Experimental models have been implemented: flat phantoms and beads made of 10% and 15% of porcine gelatin and finally porcine lenses (young: 6 months and old: 1 to 6 years). A mechanical vibrator created vibrations (0.1–3.5kHz) and an ultrafast ultrasound imaging system was used to track the propagating waves. From the curvature of the frequency domain of the cross-correlated displacement field, the wavelength and velocity were computed. Experimental models enable to validated the method with dispersion curves substantially different between both concentrations. Results in lenses are similar: a dispersion curve highly dependent of the frequency, reflecting the complexity of elastic wave propagating in a multilayered medium surrounded by a membrane. To retrieve quantitative elasticity data, advanced numerical models have to be developed. This method will be applied on lenses treated by cavitation to assess its potential for treating presbyopia.