What is the site of the crossover of nerve fibers from each eye to the opposite sides?

The crossover of nerve fibers from each eye to the opposite sides occurs at the chiasm, which is specifically known as the optic chiasm. This structure is crucial because it allows the visual information from each eye to be processed by both hemispheres of the brain. In essence, the optic chiasm enables each side of the brain to receive visual input from both the left and right visual fields, facilitating depth perception and a cohesive visual experience.

The optic nerve transmits visual information from the retina to the brain but does not involve the crossing of fibers. The retina is the layer of tissue at the back of the eye that senses light and converts it into neural signals, while the cornea is the transparent front part of the eye that helps to focus light. Neither the retina nor the cornea plays a role in the crossover of nerve fibers. Thus, the optic chiasm is the definitive site for this crossing, making it the correct answer.