Characterizing Molecular Diffusion in the Lens Capsule Problem Presenters

The lens is a transparent component of the eye which focuses light rays entering the eye to appropriate places at the back of the eye. It is tethered by muscles to the surrounding tissue and it is the movement of these muscles that alters the shape of the lens and allows focusing at different distances. The lens is sandwiched between two aqueous compartments: the aqueous humor in front of the lens and the vitreous humor behind (see Figure 1.1). The lens is an avascular tissue and relies on diffusion of nutrients and waste products for survival. It consists of highly specialized transparent cells surrounded by an outer membrane capsule. The outer membrane is a porous scaffold to which the cells underneath the membrane attach. The capsule allows force transmission and is selectively permeable. It is a complete seal around the lens and has thickness of 26 µm in a human and 10 µm in a mouse. There are various pore sizes (99 % are 4–5 nm and 1 % are about 10 nm) and these are small enough to prevent cells and some molecules from entering the layer. The scaffold is made from Collagen 4 and has sugar molecules bound on which extend into the pores and “wave in the wind”. Duncan et al. 1.