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Eye Health 101: How Does My Eye Work?

The eye is a complex organ that we often take for granted. The eye is made up of a multitude of parts, including a cornea, sclera, lens, pupil, iris, retina, and optic nerve, and it’s filled with liquid. Eyes allow us to interact with the world by converting light into electrical nerve impulses, which then travel to the brain and are transformed into visual images. These amazing organs are constantly construing the richness of life by giving color, motion, and depth to our endlessly shifting environment, so it’s worth taking the time to learn about how to keep our peepers healthy and seeing clearly.

Here are a few terms and topics you might encounter when discussing eye health:

20/20 Vision
This is simple a way to determine your visual acuity, or ability to distinguish the shapes and details of objects. Your eye doctor will use theSnellen eye chart, or that black-and-white chart with a mix of different letters, to find out if you can read a letter at 20 feet that a normal human should be able to see at 20 feet.

Color Blind Tests
Color blindness is not a type of blindness, but the inability to see or perceive color variations, such as blue and yellow or red and green. This inherited defect affects about 8 percent of men and 1 percent of women in the U.S. with red-green color vision defects being the most common. The most common test for color blindness is the Ishihara Color Vision Test, which consists of circular patterns containing many dots in a variety of colors, sizes, and brightness with an imbedded number that a person with normal vision can see.

Visual Field Tests
Used to determine your peripheral, or “side,” vision, the visual field test often consists of the eye doctor putting up different numbers of fingers within your peripheral field of view to determine how many you can see. Other more sophisticated automated tests may also be used. Poor results from a visual field test can be an important early indicator of glaucoma or optic nerve damage.

Cornea
A smooth, strong, and clear layer that covers the front of the eye, the cornea protects the eye from outside contaminants and also contributes to your focusing power. The cornea responds quickly to heal any minor scratches, but deeper cuts may require surgery. A cornea contains no blood vessels and should be transparent to provide proper vision.

Sclera
This is the tough, white outer part of the eye that makes up the supporting wall of the eyeball. It’s covered by a mucous membrane called the conjunctiva that lubricates the eye. Conjunctivitis, or pink eye, is when this layer gets inflamed from contact with contaminants like pollen or pathogens. Red, or bloodshot eyes, are caused by swollen or dilated blood vessels on the sclera that come about from allergies, fatigue, or conjunctivitis. Persistent red eyes can be a symptom of more a serious eye disease.

Retina
The retina is a layer of nerve tissue in the back of the eye that senses light and sends signals to the brain. Normally red due to its rich supply of blood, this integral part of the eye will be closely examined by your eye doctor as any changes in color or structure can suggest a serious disease.

Optic Nerve
The optic nerve is what takes the light signals from the retina and shuttles them to your brain through electrical impulses. Comprised of over one million nerve fibers, the optic nerve is most often compromised by glaucoma, where high pressure inside the eye squeezes the nerve, causing cells to die.

An easy way to give your eyes the love they deserve is by scheduling an annual appointment with an eye care professional.  Many eye diseases have subtle, if not non-existent symptoms, which only a comprehensive dilated eye exam can uncover. Risk factors that require more frequent visits include a family history of eye disease, diabetes or high blood pressure, or previous eye injuries or surgery.