Vitreous humour is a fluid with complex viscoelastic properties that occupies a near spherical volume of the eye. Saccades (movements) of the eyeball force the vitreous humour into motion, and this fluid motion has important implications for the prognosis of patients with a detached retina, and also has a crucial role in determining the locations and timescales of uptake of drugs that are present in the vitreous humour (put there either by intravitreal injection, transscleral application or topical application).
In this talk, I will present work to estimate the fluid flows that are present in a moving eye. Vitreous humour has complex properties and we present some recent experiments on its rheology. We then develop a mathematical model of the vitreous chamber and saccades. Using a Newtonian fluid approximation of the vitreous humour, the simplest model of a spherical eye with sinusoidal saccades leads to a primary oscillatory flow and a secondary steady streaming flow. The primary flow is important for determining regions of the retina that are subjected to high stress, whilst the steady component of the secondary flow plays an important role in mass transport. We also extend the model to consider the case of a generalised viscoelastic fluid model of the vitreous humour.
In reality the vitreous chamber is not perfectly spherical, and we extend the model to the near-spherical case to investigate the resulting change in the flow. Myopic eyes have shape deformations compared with normal eyes, and myopia is also associated with a higher incidence of retinal detachment; we use the model to show that the shear stress can increase significantly in a severely myopic patient.