How the Eye Sees

The main function of the eye is to convert light from the outside world into electrical nerve impulses, according to the Department of Ophthamology and Visual Sciences at the University of Illinois Chicago. These nerve impulses then travel to the region of the brain that's responsible for vision.

Function

• Light first passes through the year film of the eye then the cornea, anterior chamber, pupil, lens, vitreous and then the retina. The retina then sends impulses to the optical nerve and the brain, according to the Department of Ophthalmology and Visual Sciences at the University of Illinois Chicago.

  The round shape of the cornea allows for rays of light to bend as they pass through the anterior chamber. If the cornea is damaged, the amount of light entering the eye may become limited resulting in sight problems.

  The pupil is an opening in the eye that's responsible for controlling the amount of light that enters the eye. If the eye is exposed to bright light the pupil will constrict and become smaller to limit the amount of light that enters the eye. In the dark, the pupil does the opposite and expands to allows as much light as possible to enter the eye.

  The back of the pupil houses the lens that changes the angle of light rays that enter through the pupil and focuses them on the retina. Cataracts may develop on the lens as people age which makes it difficult to see in the dark. The lens has also been known to filter out ultraviolet rays, according to the University of Illinois Chicago.

  The retina of the eye is where photochemical reactions take place that allows the eye to see. Rods and cones in the retina allow electrical impulses to develop that are sent to the brain. Scientists often compare the retina to the lens of a camera because without the retina the eye would not be able to see.

Considerations

• Vision problems result from damage to the cornea, anterior chamber, pupil, lens, retina or vitreous, according to the Department of Ophthalmology and Visual Sciences at the University of Illinois Chicago.

Warning

• If the tear film, the outer most layer of the eye, does not completely lubricate the cornea the eye cannot see clearly, according to the Department of Ophthalmology and Visual Sciences at the University of Illinois Chicago. If the amount of tears produced is below normal it's known as dry eye, according to the Mayo Clinic. Eyes will then become irritated and have trouble seeing.

Complications

• Common eye diseases include cataracts or clouding of the lens, glaucoma which results in damage to the optic nerve because of too much pressure, conjunctivitis or pink eye and retinal disorders, according to Medline Plus .

Fun Fact

• Most people blink approximately 15 times per minute, according to the BBC. The average blink lasts between 100 and 150 milliseconds.