Preliminary investigations on cavitation effects in the crystalline lens

Abstract

Presbyopia is the age-related stiffening of the crystalline lens, reducing near vision. One of the main mechanisms of this lens stiffening is the formation of disulfide bonds. We propose ultrasonic cavitation to interact with the lens structure, disrupt disulfide bonds and restore flexibility. Here, we present early results on the feasibility of the technique. Cavitation was nucleated inside the porcine lenses using confocal transducers and signals emitted in the focal area were acquired using an imaging array and reconstructed using frequency-domain passive cavitation imaging. Peak negative pressure of 23MPa for 20-μs pulses at 1.1 MHz provided a clear chance of nucleating cavitation with our system. Exposures were performed during 10 seconds of cavitation at a PRF of 250 Hz. Cavitation clouds were clearly visible in B-mode images for both 6-months old and 3-years old porcine eyes. To provide initial safety data, the absence of cataract was confirmed on transparency images. Histology revealed no damage to the lens structure. A gel phantom with a disulfide bond-dependent hardening is proposed to investigate the potential for cavitation to disrupt the disulfide bonds.