sight.

this never ceases to blow my mind:

Sounds mysterious, even impossible, and yet the eye is one of a pair of special sense organs that converts the energy of light into electrical nerve impulses and transmits those signals to the brain where they're interpreted as sight.

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As we now know, light rays enter the eye and are refracted by the cornea, aqueous humor, lens, and vitreous humor. The rays are focused on the retina where they stimulate the rods and cones, causing chemical changes and producing impulses. These impulses are conveyed along the optic nerves to the optic chiasm. At this juncture, fibers from each optic nerve cross over to the other side. Fibers from the left visual field of each eye form the left optic tract. Impulses move along these fibers to the left visual cortex in the occipital lobe—an area in the posterior of the brain where visual stimuli is interpreted.

Fibers from the right visual fields form the right optic tract and transmit impulses to the right occipital cortex. When these images from both eyes fuse in the brain, they produce a single 3-D image, the result being called binocular vision. Convergence is the movement of the eyes in unison toward a common point of fixation. It is because of convergence that we have binocular vision, the ability to see one image using both eyes.

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Word of the day:

enucleation - removal of the entire eyeball