Viscoelastic shear properties of the fresh porcine lens

Aim: To determine the viscoelastic properties of the porcine lens Methods: Linear viscoelastic shear properties of the stroma of four porcine lenses were measured within 5 hours post-mortem, using sinusoidal oscillatory shear deformation. The elastic shear modulus, viscous shear modulus, dynamic viscosity, damping ratio, and phase shift of the lenses were quantified by a controlled-strain, linear simple-shear rheometer at frequencies of 10-50 Hz. Results: The mean viscoelastic properties and their standard deviations across the frequencies examined were: the elastic shear modulus, G′ = 6.2 ± 4.0 Pa, the viscous shear modulus, G″ = 19.2 ± 2.5 Pa, the dynamic viscosity, η′ = 0.16 ± 0.1 Pa•sec, the damping ratio ζ = 4.06 ± 1.25, and the phase shift, δ = 76° ± 5.6°. Conclusions: The measured viscoelastic shear properties of the porcine lens reflect a low dynamic viscosity with a high damping ratio. The porcine lens is viscoelastic and is more viscous than elastic. The magnitude of the complex shear modulus of the porcine lens, |G*|, is similar to the shear modulus of the young human lens. Understanding these viscoelastic properties of the natural lens may provide guidance in developing a lens substitute capable of accommodation in the post cataract patient.