Alamo Optometry Blog

June 1, 2009

How Does The Eye Work?

Filed under: Educational — Tags: — admin @ 11:32 pm

How Does the Eye Work?

(As appeared in Alamo Today, June 2009, pg. 29)

Last month I gave you an overview of our office. This month I thought I would give you an overview of the eye itself. It is an amazing organ that works in unison with our brains to allow us to visually interpret the world around us. They eye works similar to a camera. If any part of your camera is not working well, your photos will not turn out; similarly, if any of the structures or pathways of the eye are damaged, vision will be compromised.
The white part of the eye is called the sclera. The sclera is made of collagen and covers most of the eye. The clear front part of the eye is called the cornea. The cornea is where contact lenses are placed and is the first structure that light comes in contact with on its way to being focused on the retina.
Your pupil is the round black circle in your eye that gets bigger and smaller depending on the amount of light. The iris is the colored muscle fibers surrounding the pupil and controls the size of the pupil. The pupil and iris are like a camera’s aperture which is an open space that allows the light to pass through farther into the eye. Between the iris and cornea is the anterior chamber. This chamber is filled with a special fluid that gives the front part of the eye oxygen, protein, and glucose to keep it healthy. The light then travels to the lens of your eye.
The lens is similar to the lens of a camera; they help to bring the light into focus. The lens bends light further and sends it to the back of the eye. The lens is suspended in the eye by a bunch of fibers. These fibers are attached to a muscle called the ciliary muscle. The ciliary muscle changes the shape of the lens. When you look at things up close, the lens becomes thicker to focus the correct image onto the retina. When you look at things far away, the lens becomes thinner.
The biggest part of the eye sits behind the lens and is called the vitreous body. The vitreous body forms two thirds of the eye’s volume and gives the eye its shape. It’s filled with a clear, jelly-like material called the vitreous humor. After light passes through the lens, it shines straight through the vitreous humor to the back of the eye.
In the back of the eye is the retina. The retina contains photoreceptor nerve cells called rods and cones. Each eye has about 120 million rods and 7 million cones. The cones are mainly in the macula, the center of the retina. The cones are responsible for sharp vision and color vision. The rods are situated in the periphery of the retina and allow us to see at night. These cells take the light and transform them in to electrical impulses. These electrical impulses are then sent to the optic nerve. The optic nerve then transmits the information to the brain. Using a camera demonstration, you can call the retina the film of the camera. If your film goes bad you will not be able to view any pictures no matter what you do. The same goes with the retina. If the retina is damaged by macular degeneration or diabetes, you are not going to be able to fully process any pictures or images.
How the eye processes light is only part of the process. When you do not see well, the problem might be simple in that you are near-sighted or far-sighted and just need glasses or contacts. Also, any disease or trauma to any of the above-mentioned structures can be a cause of decreased vision. Anything from cataracts (clouding of the lens), diabetes, glaucoma (optic nerve deterioration), to almost any systemic disease can cause vision and ocular health concerns. That it why comprehensive exams with dilation that test more than vision alone can help ensure that the entire eye system is working as well as possible.

Dr. K. at Alamo Optometry is your hometown eye doctor for outstanding service, vision care, and designer eyewear. He can be reached at 925-820-6622 or visit his office at 3201 Danville Blvd., Suite 165 in Alamo.

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