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Vision 101: Facts About the Human Eye

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Updated October 12, 2011

Your eyes are very complex organs. In order for your eyes to see, there must be light. Light rays reflect off of an object and enter the eye through the cornea. At the back of your eye the light is focused by the retina, then it is converted into electric signals to be sent to the brain. Once the brain receives the signals, vision occurs.

If your eye cannot properly focus an image, it is said to have a refractive error. An eye doctor can determine the type of refractive error by a test called a refraction. Correcting a refractive error is achieved by glasses, contacts or refractive surgery. This is basic human vision.

Visual Acuity and Refractive Errors:

Visual acuity is a measure of the clarity and sharpness of your vision. Measuring your visual acuity is a quick method for a health care professional to discover vision problems. Normal visual acuity is usually expressed as 20/20 and indicates the smallest detail a person should be able to see at a standard testing distance of 20 feet. Visual acuity test results help health care professionals determine if you may be nearsighted, farsighted or have astigmatism.

Correction Options:

Vision can be corrected in many ways. Eyeglasses improve vision by bending light. They are safe, economical correction devices. Another vision correction option is contact lenses. People with active lifestyles enjoy wearing contact lenses because they stay in place better than glasses. Corrective surgery is yet another way to correct vision problems. Refractive surgery reshapes the eye to normalize its light bending abilities so that the quality of vision is improved without the use of additional visual aids.

Age-Related Complications:

As we age, the likelihood of developing certain eye conditions and diseases increases. The decreasing ability to focus at close range is known as presbyopia, a condition normally seen in people over forty. As we age, especially in our sixties, the natural lens of the eye also begins to get cloudy, a condition called a cataract. With that change, our need for increased light and better contrast changes as well. Finally, as we age, the risk of developing dry eye syndrome, macular degeneration and cataracts is much greater.

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