The outer most surface of the eye, or the clear outer structure is called the cornea. This is the only part of the eye that can be transplanted, that is, there is no such thing as an eye transplant. The cornea's primary function is to bend light rays coming into the eye so that it focuses them on the retina. As we stated earlier, the retina is the inner layer of the back of the eye and is much like a relay station. The first area touched by light rays are the rod and cone cells.
Cone cells live primarily in the macula while rod cells live in the peripheral retina.
Rods and cones are like rabbit ears on a TV set. They help catch the light rays that are focused on the retina. The disease of macular degeneration is being studied to determine if there is an abnormality in the rods or cone cells or if the primary problem is in a layer of cells below the rod and cone cells called the RPE cells. These cells called the retinal pigment epithelial cells is a layer of cells like a carpet underneath the rods and cones. The primary purpose of this layer is to hook up with the rods and cone cells to bring nourishment for healthy tissue.