Optic Chiasm: X Marks the Spot:
• Emerging from the retina of your eye, the axons (colored red in the left image) come together at the blind spot, where about 1 million of them exit the eye to form the optic nerve. The blind spot has no visual cells, but you don’t notice it because when both eyes are open, they compensate for each other. To “see” your blind spot, follow the instructions on this link : http://goo.gl/HKB2s
• At the bottom of the brain, the optic nerves cross over in the chiasma (from the Greek χιάζω ‘to mark with an X’, after the Greek letter ‘Χ’, chi). Because we have binocular vision, signals from part of one eye cross over to the opposite side of the brain while the rest is deciphered by the same side. This means that each half of the brain receives visual signals from both eyes. The chiasma of the mouse brain (right image) shows nearly complete crossing over because rodents have poor binocular vision.