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NIH MedlinePlus the Magazine, Trusted Health Information from the National Institutes of Health


Understanding Your Vision: The "Imperfect Eye"

Two young boys holding soccer balls.

Photo courtesy of National Eye Institute, NIH

Everyone's eyes are different and so are the types of vision that we have. Understanding how some of us see differently and how the eyes change over time, will help protect your vision.


Normal vision, often called "20/20" vision, means that you can see clearly objects that are 20 feet away. However, 20/20 does not necessarily mean perfect vision. There are other important vision skills, including peripheral awareness (side vision), eye coordination, depth perception, focusing ability, and color vision that make up your overall visual ability.


If you are nearsighted—also called myopia— you can clearly see close objects, but distant ones are blurry. The more nearsighted, the blurrier your distance vision and the closer objects need to be to be seen clearly.

Treatment helps to focus light on the retina through the use of corrective lenses or "refractive" surgery.

  • Corrective lenses include eyeglasses and contact lenses, both of which come in a variety of styles and can correct a number of problems at once.
  • Refractive surgery reshapes the curvature of the cornea and includes several types of laser surgery (such as LASIK) and regular surgery, including an implanted set of lenses.

"Keeping your eyes healthy means learning about them and the conditions for which you may be at risk."

— Dr. Emily Chew
National Eye Institute


If you are farsighted—have hyperopia—you can see distant objects clearly, but close ones are blurry. Farsightedness occurs when the eyeball is too short for light rays to focus clearly on the retina.

Treatment helps to focus the light through the use of corrective lenses or refractive surgery, as with nearsightedness. Most young people's eyes are flexible enough to focus on nearby objects, so they don't need corrective lenses. But by middle age, the natural lenses become less flexible. Corrective lenses, either eyeglasses or contacts, are necessary to improve vision at this point. Refractive surgery reshapes the curvature of the cornea with the same methods used for correcting nearsightedness. Conductive keratoplasty (CK), which uses radio-frequency energy to apply heat to tiny spots around the cornea, is an additional treatment.

To Find Out More

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If you have astigmatism, the cornea is more oval than round. This doesn't allow the eye to focus clearly. Astigmatism is usually accompanied by nearsightedness or farsightedness.

Treatment addresses the cornea's uneven curvature through corrective lenses or refractive surgery. Orthokeratology, or Ortho-K, is also used to correct astigmatism. In this procedure, you wear rigid contacts for several hours a day until the curvature of the eye improves. After that, you wear the lenses less frequently to maintain the new shape. If you stop treatment, the eyes return to their former shape.

Age-related Blurriness

Beginning at about age 40, most people have to begin holding the newspaper or their favorite book at arm's length in order to see clearly. At the same time, they may still clearly see far away objects. This is a common age-related blurriness called presbyopia. This process actually begins around age 10, but vision changes aren't noticeable until many years later.

Treatment is through corrective lenses or several of the refractive surgical procedures mentioned for nearsightedness and farsightedness.

A photo of a boy with Amblyopia.

Photo courtesy of National Eye Institute, NIH

AMBLYOPIA: Sometimes known as "lazy eye," amblyopia is the most common cause of visual impairment among children. The condition affects about two-to-three out of every 100 children. Unless it is successfully treated in early childhood, amblyopia usually continues into adulthood, and is the most common cause of monocular (one-eye) visual impairment among children and young and middle-aged adults.

Helping kids overcome serious vision impairment is at the heart of the Pediatric Eye Disease Investigator Group (PEDIG), a collaborative multi-center network begun in 1997 and funded by NEI. It includes 120 researchers at 60 sites in the United States and Canada who clinically study amblyopia and other eye disorders of children.

Treating amblyopia involves making the child use the weaker of the two eyes by patching the stronger eye or using an eye drop called atropine to temporarily blur the vision in the stronger eye. Treatment, which may take weeks or months, stimulates vision in the weaker eye and helps the part of the brain that manages vision develop more completely. Nationwide studies conducted by PEDIG doctors have helped find ways to make amblyopia treatment as successful as possible and shown that many children ages 7 through 17 with amblyopia may benefit from treatments that are more commonly used on younger children.

Summer 2008 Issue: Volume 3 Number 3 Pages 12 - 13