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Eye Anatomy CE - Sight

The Optic Nerve

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Optic nerve head and blood vessels
The optic nerve pathway from each eye as it passes through the optic chiasma and travels to the occipital lobe at the back of the brain.

The optic nerve is composed of the ganglion cell axons, or nerve fibers, from the retina. Wrapped within the optic nerve are the central retinal artery, whose branches supply 30% of the retina's metabolic needs, and the central retinal vein, which collects blood from the branches of the retinal artery.

Emerging from their separate globes, the optic nerves from each eye meet at the optic chiasma located at the base of the brain. At this point, half of the axons from each nerve cross over into the other nerve, so that some visual information from the left eye travels in parallel with information from the right eye within each of the two nerves.

This partial crossing over of visual information from both eyes to opposite sides of the brain allows the coordination of images from both eyes. Since the eyes see the same objects from slightly different angles, the images will be slightly different. The brain's interpretation of image differences allows you to perceive depth of field, and gives you an estimate of the distance between you and the object.

From the optic chiasma, the axons continue to two regions on either side of the center of the brain, called the left and right lateral geniculate nuclei. The axons then form synapses with brain neurons, which travel to the rear of the brain, to the left and right primary visual cortices.