Vitreal Viscoelasticity Revealed by Motion-Encoded MRI

Introduction: Retinal detachment results in visual loss and requires surgical treatment. The shear stress induced during eye movement by the vitreous on the retina can damage the retina. The following filling of the subretinal space with liquefied vitreous induce the detachment of the retina. Changes in the vitreous viscoelasticity impact on the shear stress. Up to now, the viscoelasticity of the vitreous has been measured ex-vivo and varied in function of the sampling location inside the eyeball. Further, the vitreous deformation during eye movement has been simulated as a spherical homogenous fluid rotating around a diameter. This analytical model uses two parameters (a and b, from which the viscosity and elasticity can be derived), and makes the assumption of homogeneous viscoelastic properties throughout the vitreous. The reported viscoelasticity was used to describe the vitreous deformation, as shown in Fig3C for 12 concentric circle (perpendicular to the rotation axis, with radii ranging from 1-12 twelfths of the eyeball radius) during sinusoidal eye rotation (±20° amplitude, 2s period). However, the vitreous is divided into sectors by intravitreal membranes. These intravitreal membranes may separate the vitreous into regions of different viscoelasticity and may also directly impact on the vitreous rheology. Here we present a MRI method to determine the vitreous deformation and viscoelastic properties in-vivo and clarify the role played by the intravitreal membranes.