Steady Streaming in the Liquefied Vitreous Due to Saccadic Eye Movements

The posterior chamber of the eye has an approximately spherical shape, and is filled with vitreous humor, a transparent material with viscoelastic properties [1]. The vitreous has the mechanical roles of supporting the eye shape, promoting the adherence between the retina and the choroid, and acting as a barrier between the anterior and posterior segments of the eye that inhibits both heat diffusion and molecular transport [2]. Sometimes, particularly in elderly people, the fluid in the posterior chamber has almost Newtonian properties. This can be as a consequence of liquefaction of the vitreous humor due to synchisys (degradation of the collagenous framework of the vitreous humor), or after a vitrectomy, a surgical procedure in which the vitreous humor is replaced by tamponade fluids (typically silicone oils). Since intra-vitreal drug injection is increasingly used to treat retinal diseases, and the efficacy of this procedure depends on molecular transport processes following injection, much of the biomechanical research on the vitreous humor has focused on understanding these processes. Many authors have considered purely diffusive transport or alternatively purely advective transport due to creeping bulk flow [3,4]. However, when the vitreous is liquefied, rotational motion of the eye is also likely to induce significant fluid flow.