How Does the Eye Work?

How Does the Eye Work?

We use our eyes everyday without really understanding how they work.

The human eye is a miracle. It adapts to different lighting conditions and uses light rays to focus itself. When all of the parts of the human eye work right, light is translated into nerve impulses and transmitted to the brain, where we think of those impulses as “images”. The whole thing takes place without any influence or human input. Our eyes are like extremely high-tech cameras stuck into our heads, and most of us have no idea how it is they actually work.

Like a Camera

When we say that our eyes are like cameras, we aren’t really that far off. Each individual part of the human eye works together much like our modern cameras.

Each part of the eye plays a distinct and necessary role in doing what eyes do best — giving us clear accurate vision. If the eye is a camera, then the cornea is like a lens cover. The cornea is the main focusing part of the eye. Our corneas take rays of light from all over the place and “bend them” through our pupils — the pupil is the dark round opening in the center of the colored iris. The iris and pupil act like the aperture of a camera — the hole that allows light in for a brief instant.

The Lens

After light moves through the iris and pupil, the lens acts just like the part we call a “lens” in a camera. The lens in our eyes helps us to focus the light that the cornea received to the back part of the eye. The “lens” is the part of the eye that people these days have laser surgery on to improve vision. It is also the part of the eye that gets cloudy when a person has cataracts. Artifical lenses are now available for people with lens problems.

The very back wall of the eye is super important to our vision. It is lined with a layer that we call the “retina” which acts like the film in a film camera. The retina is a membrane chock full of nerve cells called “photoreceptor cells” that change the light rays our corneas captured into electrical impulses. These impulses are then sent down the optic nerve where they eventually end up in our brain. These impulses are translated into vision. Just like with a film camera, if the “film” (the retina) is damaged, you won’t have good vision no matter how good the rest of your eye is. That’s why retina damage is so serious.

Other Parts of the Eye

The center of the retina (about 10% of your eye) is called the “macula”. This part of the eye is responsible for close-up and sharp vision, the vision you use to read.

Another part of the eye is the peripheral retina which handles all your peripheral vision needs.

Taking good care of your camera is important to having a quality life. Damaging any part of your eye can mean decreased or even lost vision. Maintaining eye health is a matter of consuming the right vitamins, keeping your eye clean of debris, and not exposing your eyes to light that is too bright.

This is part of a series of blog posts we’re publishing about How Stuff Works. The other posts in this series include: