How The Eyes Work

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You open your eyelids, point your eyes at something, and you see it – right? Yep. Blog over, thanks for pointing your eyes at this page!

Okay, in case you want more info, I guess I can expand on that explanation a bit…

On one hand, the explanation above is accurate. How can we argue against a person’s experience when they wake up every day? You open your eyes, look, and see stuff. That’s totally true, but it’s also a very simple explanation of the ridiculously complex piece of machinery that is the human eye.

On the other hand, the explanation above has some problems. One is how we tend to describe our eyes as actively looking at things. We talk as if our vision is like a laser beam that we can point at things to inspect them. In reality, our eyes are passive in relationship to our environment.

Our eyes are constantly under attack, and I’m not talking about dust, pollen, or children with sharp sticks. I’m talking about light. Light attacks our eyes from all angles (usually in a gentle, friendly way). It reflects the environment around us, demanding that we see it. Whether you want to or not, your eyes see everything in your field of vision. There’s no escape.

Fortunately, you can control whether something comes into focus, or remains as a blurry backdrop. To explain what the eye does, I think it’s helpful to look at what light does as it enters our eyes:

Light’s Journey to your Brain

Funnels and Filters

The front parts of the eye are basically sophisticated kitchen tools that reduce the amount of light allowed inside your eye. The cornea (transparent outer layer of the eye) funnels the light from your entire field of vision into a more manageable area for the rest of your eye to work with. The iris and pupil (the colored and black portions of the eye) work together like an adjustable sieve to allow the appropriate amount of light in.


At this point, light is feeling a little discouraged. Its near-infinite army of would-be eye invaders has been narrowed and thinned dramatically. And now it’s about to be channeled even further by the lens (a clear, flexible structure behind the iris).

The End of the Journey

The lens takes the remaining funnel of light (see image below), and reduces it to a sliver, which comes to a sharp focal point on the retina (the back wall of the eye, which serves as a projector screen for your brain). Once light hits the retina, its journey is complete. Shapes and colors are converted into nerve messages, and sent through the optic nerve (a high-speed communication channel) to the brain for interpretation.

Focus on Focusing: The Lens

The lens has the important job of corralling all the light that comes through it into that sharp focal point. To do this, it uses specialized muscles in your eyes to change its shape. A different shape is needed to focus on objects at different distances, and the lens reflexively adjusts its dimensions to the shape required to see an object clearly.

This flexibility of the lens allows you to focus on objects near and far.

However, if you are nearsighted or farsighted, your lens is unable to change itself into the shape required to see clearly at certain distances. Fortunately, a VSP Doctor can detect the level of assistance your lens needs to be able to focus, and they can prescribe the appropriate glasses or contact lenses.

What to Do To Protect Your Vision

Get your eyes checked regularly. As your eyes lose the ability to focus well as you age, help your eyes tell your brain what’s going on in the world!

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