Vision is our most "dominant" sense. First, light enters the eye; then, organs in the eye perform transduction, turning visual signals into neural impulses. Then, neural impulses are transported to the Occipital Lobe's Visual Cortex and interpreted.
The white of your eye is called the sclera covered by the thin conjunctiva. This is a protective layer which covers the entire eyeball except the cornea. The cornea is transparent and it allows light to enter the eye.