Vision and the brain. Coloured Magnetic Resonance Imaging (MRI) scan of an axial section through the head of a 55 year old man, showing the eyes, optic nerves and brain. Bones of the nose are at upper centre. The eyes (pink circular structures) reveal eye muscles around them and a long optic nerve which extends from each eye towards the brain. At lower centre is the optic chiasma (X shape), where the optic nerve from the left visual field goes to the right hemisphere of the brain, and vice versa. The folded cerebrum of the brain is yellow (at lower frame). MRI scanning uses a powerful magnetic field and radio waves to produce insslicesins through the body to reveal human anatomy in great detail.