Assessment of the influence of lens capsule on lens biomechanical properties with Optical Coherence Elastography

The crystalline lens is enclosed in a membrane, which presses upon the lens molding it into the required shape to enable dynamic focusing of light. Yet, the effect of the capsule membrane characteristics on the lens biomechanical properties has not been fully investigated. In this study, the lens viscoelasticity was assessed using phase-sensitive spectral-domain optical coherence tomography (PhS-OCT) coupled with acoustic radiation force (ARF) excitation before and after the capsular bag was dissected away. The ARF excitation was focused on the anterior pole of the lens, and two orthogonal MB mode scans were performed for each lens sample before and after removal of the lens capsule. The resulting elastic wave group velocity, V, in the lens with capsule intact (V = 2.60 +/- 0.21 m/s) was found to be significantly higher (p <.001) than after the capsule was removed (V = 1.14 +/- 0.15 m/s). Similarly, the viscoelastic assessment using surface wave dispersion model showed that both the Young's modulus and shear viscosity of the encapsulated lens (E = 8.14 +/- 1.10 kPa, eta = 0.89 +/- 0.093 Pa.s) was significantly higher than that of the decapsulated lens (E = 3.10 +/- 0.43 kPa, eta = 0.28 +/- 0.021 Pa.s). These findings, together with the geometric differences between encapsulated and decapsulated lens as quantified from structural OCT images, indicate that the capsule is a key lenticular component that determines the stiffness and structural integrity of the lens.