Hexagonal cells of<unk>  visualized by specular microscopy. The principal physiological function of the<unk>  is to allow leakage of solutes and nutrients from the aqueous humor to the more superficial layers of the<unk> while at the same time pumping water in the opposite direction, from the stroma to the aqueous. This dual function of the<unk>  is described by the "pump-leak hypothesis." Since the<unk> is avascular, which renders it optimally transparent, the nutrition of the<unk>  epithelium, stromal keratocytes, and<unk>  must occur via diffusion of glucose and other solutes from the aqueous humor, across the<unk> . The<unk>  then transports water from the stromal-facing surface to the aqueous-facing surface by an interrelated series of active and passive ion exchangers. Critical to this energy-driven process is the role of Na+/K+ATPase and carbonic anhydrase. Bicarbonate ions formed by the action of carbonic anhydrase are translocated across the cell membrane, allowing water to passively follow.
Corneal endothelium
Iris pigment epithelium
Corneal keratocyte
Retinal nerve fiber layer
Retinal ganglion cell
Layer of rods and cones
Corneal limbus
Macula of retina