Quantitative evaluation of biomechanical properties of optic nerve head by using acoustic radiation force optical coherence elastography

Previous studies have demonstrated that the biomechanical properties of the optic nerve head (ONH) are associated with a variety of ophthalmic diseases; however, they have not been adequately studied. We aimed to obtain a two-dimensional (2D) velocity distribution image based on the one-to-one correspondence between velocity values and position using the acoustic radiation force optical coherence elastography (ARF-OCE) technique combined with a 2D phase velocity algorithm. An ARF-OCE system has the advantages of non-invasive detection, high resolution, high sensitivity, and high-speed imaging for quantifying the biomechanical properties of the ONH at different intraocular pressures (IOPs) and detection directions. The 2D phase velocity algorithm is used to calculate the phase velocity values at each position within the imaging region, and then the 2D velocity distribution image is realized by mapping the velocity values to the corresponding structure based on the one-to-one relationship between velocity and position. The elasticity changes can be read directly according to the quantitative relationship between Lamb wave velocity and Young's modulus. Our quantitative results show that the phase velocity and Young's modulus of the ONH increase by 32.50% and 129.44%, respectively, with increasing IOP, which is in general agreement with the results of previous studies, but they did not produce large fluctuations with the constant change of the ONH direction. These results are consistent with the changes of elastic information in the 2D velocity distribution image. The results suggest that the ARF-OCE technology has great potential in detecting the biomechanical properties of the ONH at different IOPs and directions, and thus may offer the possibility of clinical applications.