Your cornea needs to be properly lubricated by the tear film secreted by tiny glands in your eyelids. It functions like the focus ring on your camera's lens. The light finally is absorbed by photoreceptors in the retina. These are known as rods and cones. Rods provide your side and night vision.
Cones provide colour, detailed central vision.
You are using your cones to read this. The rods and cones turn light into an electrical impulse which is modified by other nearby cells and in turn sent along the optic nerve to the back of the brain to be turned into pictures. This is a photo of the back of the normal eye, as seen by eye doctors. By using special instruments it is possible to look directly at the retina, the optic nerve and other structures within the eye. Radiating from it are retinal arteries and veins.