Characterization of biomechanical properties of crystalline lens using Brillouin microscopy and optical coherence elastography

Abstract

The biomechanical properties of the crystalline lens play a crucial role in its visual function. Assessing biomechanical properties of the lens may help with early disease detection and robust assessment of therapeutic interventions. However, measuring the biomechanical properties of the lens is a challenge due to its location inside the eye-globe. In this study, we demonstrate the combination of optical coherence elastography (OCE) and Brillouin microscopy to evaluate the stiffness of porcine lenses ex vivo (N=6). Brillouin microscopy can map the Brillouin-derived longitudinal modulus of the whole lens, but imaging times are lengthy. OCE can provide quantitative measurements of viscoelasticity rapidly, but the limited scattering of the lens limits its in-depth measurements. By combining these two techniques, we show a strong correlation between the Brillouin modulus and OCE-measured Young’s modulus in the lens, enabling depth-wise mapping of the Young’s modulus. The correlation coefficient between the two measurements was R=0.89. Using this correlation, the elasticity of the anterior lens was 2.72±0.89 kPa, and the mean Young’s modulus of the nucleus was 12.92±2.75 kPa. Similarly, the elasticity of the posterior lens was 3.80±1.25 kPa. While both techniques can evaluate the stiffness of the biological tissues separately, our work demonstrates that combining these techniques could enable mapping of the Young’s modulus completely noninvasively in non-scattering tissues such as the crystalline lens.