3D numerical investigation of the fluid mechanics in a partially liquefied vitreous humor due to saccadic eye movement.

Partial vitreous liquefaction (PVL) is a common physical and biochemical degenerative change in the vitreous body in which the liquid component becomes separated from collagen fiber network and this might form the pocket of liquefaction known as lacuna. The main objective of this research is to investigate how the saccade movements influence flow dynamics of the PVL. A three-dimensional model of the vitreous cavity is subjected to saccadic movement and the numerical simulations for various saccade amplitudes and volume fractions are performed. We consider concentric and eccentric configurations of the PVL with the initial spherical shape inside a spherical cavity. In this paper, a specific 3D numerical solver is developed to capture the interface effects and dynamic characteristics of a two-phase viscoelastic-Newtonian fluid flow by using the OpenFOAM CFD. The code is based on a set of time-dependent non-linear partial differential equations (PDE) such as continuity, momentum and constitutive relation for polymeric stresses tensor. The finite volume method with a modified volume-of-fluid model and dynamic mesh technique are used to solve PDEs. Firstly, the validity of the present numerical model was verified by comparing the obtained results with the analytical solutions which demonstrated remarkable agreement. Then, the time- and space-dependent velocity field, shear stress and normal stress distributions were computed and how the PVL responds to the saccadic motions was discussed.