Inside the Amazing Eye
Have a look
inside the eye!
Twinkle
RetinaIris
MaculaCornea
Optic NervePupil
VitreousLens
Click on the names of the parts of the eye to learn more!


How the Eyes See:
Light's Amazing Journey into the Brain

  1. Light enters the eye, first passing through the outer, transparent layer of the eye, called the cornea.

  2. Through the cornea, the light next passes through the pupil. The pupil gets bigger to allow more light in (when there's very little light) and smaller to allow less light in (when there's a lot of light).

    How does the pupil know to get bigger or smaller? That's the job of the iris. The iris is the colored part of your eye, and it controls the pupil's size.

  3. Once the light passes through the iris, it next hits the lens The lens puts the light rays into focus and sends it to the retina. But before it hits the retina, it has to pass through...

  4. VITREOUS HUMOR!!! This is a colorless mass of jelly-like material that lives in the eye behind the lens. The light passes through this material, where it finally reaches...

  5. The retina, which is the innermost layer of the eye. Think of the eye as a camera. The retina, then, is the film in the camera which captures the image.

    The funny thing is that the image on the retina appears upside-down, backwards, and 2-dimensional. But when we think about how we see things, they're always right-side-up and 3-dimensional. Something else has to happen before this journey is over...this light-information has to be sent to the brain.

    The retina contains light-sensitive cells called rods and cones. These cells are what connect with the brain through a very important nerve at the back of the eye called...

  6. The optic nerve. This nerve is the brain's messenger, sending the image to a place in the back of the brain called the occipital lobe. Its at this point that the brain is able to switch that backwards, upside down, 2-dimensional image into its correct form.

    How does the brain turn a 2-dimensional image into a 3-dimensional image? You need to remember that you have two eyes, each carrying this light information to the brain from 2 slightly different angles (your eyes are several inches apart, and that gives each eye a slightly different view on the world). When the brain receives both of these 2-dimensional images, it combines them together into one 3-dimensional image, allowing you to see the world in 3D!

Phew! What a journey! Just imagine how many times a day light takes that journey through your eyes. The number would be too many times to count. It happens all the time, and you don't even have to think about it. Your eyes just do it! The eye is truly amazing.

 
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image c. 1999, American Association of Opthamology