Understanding Your Vision

What is vision?

Vision is the ability to see. To have vision, you need light and the use of your eyes and brain. The eye is made of different parts that work together. They take the image reflected by light, focus it properly, and then send this message to the brain.

What are the parts of the eye and how do they work?

  • The outside clear layer in the front of your eye is the cornea. Around the cornea is the white part called the sclera. Light rays enter your eye through the cornea as they bounce off the object you are looking at. The light then passes through the pupil, which is the black circle in the middle of the iris. The iris is the colored part of your eye. This controls how much light is needed as it goes into the eye for you to see well. The iris closes the pupil in bright light and opens it when the light is dim.

  • Behind the iris is a clear lens that changes shape as you look at objects at different distances. Light goes through this lens on its way to the retina at the back of the eye. The retina is a special layer of nerves on the back inside wall of your eyeball. The retina turns the light rays into images or pictures and sends them to the brain as impulses (signals). The brain combines the images that each eye sees to make one picture. It also helps you understand what you are seeing.

What are the different eye problems affecting vision and how are they treated?

Problems with vision often occur along with conditions affecting one or more parts of the eye. To know these, your caregiver may do certain tests to check your eyes. Treatment will be based on what is causing your vision problem and which will work best for you. Ask your caregiver for more information on the following conditions and their treatment:

  • Amblyopia: This is also called lazy eye. One eye has poorer vision than the other. This happens when the brain receives unequal messages from the two eyes and favors one eye instead of both. Wearing glasses or a patch over the good eye may help correct amblyopia.

  • Eye diseases: Eye diseases may occur along with other medical conditions or with aging. These are often found through tests that check the inside of the eyes. If not treated or controlled early, these diseases can severely affect vision, leading to partial or complete blindness. Treatment may include medicines, surgery, or both. Some of the common eye diseases include the following:

    • Age-related macular degeneration: This disease affects an area in the middle part of the retina called macula. It causes blurring or loss of vision in the center of your eyesight which is needed for activities, such as reading and driving.

    • Cataract: The lens of the eye becomes cloudy making it hard for light to pass through.

    • Diabetic retinopathy: High blood sugar levels caused by diabetes damage the blood vessels of the retina.

    • Glaucoma: This disease usually happens when the pressure inside the eyes is increased. This condition may damage the optic (eye) nerve.

  • Refractive errors: Problems in the way the eye is built affect the eyes' ability to focus the image correctly. Eyeglasses or contact lenses can correct the problem. Surgery, such as laser, may also be used especially in severe cases.

    • Astigmatism: This condition is marked by an uneven and curved cornea, instead of being round and smooth. This causes distorted vision for both near and far objects. Astigmatism may happen along with myopia or hyperopia.

    • Hyperopia: This is also called farsightedness. Objects that are far away are clearly seen while those near are blurred. This happens when the eye is shorter than normal so light gets focused behind the retina instead of on it.

    • Myopia: This is also called nearsightedness. This condition may cause you to clearly see objects up close but not those from afar. Myopia happens when the eye is longer and more oval than normal. This causes the light to be focused in front of the retina instead of on it.

    • Presbyopia: This condition occurs with aging. The lens of the eyes begins to get less flexible, making it hard to focus objects that are up close.

  • Strabismus: This is also called crossed eyes or wall eyes. The eyes do not point in the same direction or do not move together. This causes one eye to be turned in or out.

  • Other vision problems:

    • Color blindness: This is the inability to see or differentiate some or all colors. Color blindness may run in families or as a result of injury to the eye, nerve, or brain.

    • Low vision: Normal vision cannot be achieved even with the use of corrective glasses or contact lenses. Daily activities are limited because of the poor vision. Visual aids, such as magnifying glasses, or devices, such as talking watches may help people with low vision.

    • Legal blindness: This means that a person has either a very poor visual acuity or a tunnel vision (very small field of vision). Visual acuity measures how clear or sharp one's vision is. In the United States, a visual acuity of 20/200 or worse in the better eye while wearing corrective lenses falls under legal blindness. This means that a legally blind person needs to stand 20 feet from an object to see what a person with normal vision can see from 200 feet. Legal blindness also includes those whose field of vision in the better eye is limited to 20 degrees.

How can I keep my eyes healthy?

  • Have regular eye checks: It is important to have a complete eye exam regularly. This includes tests that may help learn about your vision and check for signs of eye problems. Caregivers recommend having an eye check at least every few years until you are 40 years of age, then every 2 to 3 years thereafter. People with risk factors, such as diabetes or hypertension (high blood pressure), should have their eyes checked often. Ask your caregiver for more information about eye checks.

  • Prevent eye injuries: Protect your eyes by wearing safety glasses, eye shields, or goggles when working with power tools, gardening, or playing sports. If you are wearing contact lenses, make sure you use, clean, and store them correctly. Know when and how long they can be used.

What should I do if an eye injury occurs?

The following are first aid treatments for some of the common eye injuries. Make sure to have a caregiver check your eyes. Any eye injury may be more serious than what it seems.

  • Blows: If your eye gets hit, apply cold cloths on your eye for 15 minutes. This will help decrease swelling, pain, and redness around your eye.

  • Cuts or punctures: If an object gets stuck in your eye, do not pull it out or try to remove it. Put a loose bandage on your eye and seek care immediately.

  • Chemical burns: If a chemical gets into your eye, wash it out with water for at least 10 minutes. Chemicals may include cleaning fluid. Have your caregiver check your eye right away.

  • Foreign object: Wash your eye with water if sand, dust, or other foreign objects get into your eye. Do not rub your eye.

Where can I find more information?

Contact the following for more information:

  • American Academy of Ophthalmology
    655 Beach St.
    San Francisco , CA 94109
    655 Beach St.
    San Francisco , CA 94120-7424
    Phone: 1- 415 - 561-8500
    Web Address: http://www.aao.org/
  • National Eye Institute, National Institutes of Health
    202 Vision Pl.
    Bethesda , MD 20892-3655
    Phone: 1- 301 - 496-5248
    Web Address: www.nei.nih.gov

Care Agreement

You have the right to help plan your care. Learn about your health condition and how it may be treated. Discuss treatment options with your caregivers to decide what care you want to receive. You always have the right to refuse treatment. The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

© 2013 Truven Health Analytics Inc. Information is for End User's use only and may not be sold, redistributed or otherwise used for commercial purposes. All illustrations and images included in CareNotes® are the copyrighted property of A.D.A.M., Inc. or Truven Health Analytics.

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