Vancouver Optometrists

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THE EYES — Part 2 of 3

Monday, October 26, 2015 @ 09:10 PM
Author: Amit Mathur


Last week, we went through the different parts of the eyes, including the iris, the pupil, the sclera and the cornea. This week, we examine the lens, the retina and how they work together to process light and how your eye muscles and your brain translate this information into vision.

When The Moon (or Light) Hits Your Eye Like A Big Pizza Pie… That’s Vision!

Once light goes into your eye through the pupil, it automatically hits the lens. The lens is located behind the iris and is transparent, so you can’t really see it (unless you have special machines like the doctors). The retina, situated at the very back of the eyeball, receives the light rays that have been received by the lens. The retina has millions of light-sensitive cells (called rods and cones) that convert the light information into nerve signals that are sent to the brain which translate information into vision.

Think of the lens in your eye like a movie project at your local Cineplex Theatre. If you’ve ever looked behind you to the top of the projection booth, you’ll notice light coming from that little window. That light has passed through a powerful lens and focuses the movie’s images onto the big screen in front of you. If you think about this example in terms of your eyes, the movie screen at the front of the theatre is like your retina.

Eye Muscles

The next big factor in vision, involves the muscles of the eyeballs. Lenses are held up in place by a grouping of fibers that are attached to the ciliary muscle. This muscle can actually change the thickness of your lens. For instance, if you are looking at objects that are close, your lens needs to be thicker however when you are looking at objects that are further away, the lens becomes thinner. This helps the lens process the image you are looking at and focus the right image on the retina. Just like how your camera has to refocus depending on whether you are taking a photograph of a flower close up, or mountains in the background.

The Vitreous Body

What you see when you look in the mirror is typically just the eyeball (or there’s the lids too), but what you don’t realize is that your eyes are like icebergs: two thirds of your eyes are found behind the eyeballs. This main part of your eye is called the vitreous body and gives the eyes its round shape. The vitreous body consists of a clear, gelatinous material called the vitreous humor and serves to direct the light that has gone through the lens to the back of the eyes.

The Brain

Now think of the nerve that connects to your eyes from behind (called the optic nerve), as the messenger of sight. The cells inside the retina convert the various objects and shapes and colours you see into messages that the optic nerve can carry to the brain. Think of your optic nerve as your high-speed internet cable that connects your laptop with the web. When you see something, it’s important that the information you are seeing be translated into bits and bytes (or 1s and 0s), so that your brain can understand it.

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