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MYOPIA (Nearsightedness)
Excerpted from Triad's Eye Care Notes 1989-2005 by Triad Publishing Co.

When you are nearsighted (myopic), your vision is clear for objects close to your eyes, but blurred for everything in the distance. If a child cannot see the blackboard clearly from the back of the classroom, chances are that he or she is nearsighted.

Myopia comes in all degrees, from minimal to extreme. The more myopic you are, the more blurred your distance vision, but the closer up you can see clearly -- your range of clear vision is closer to your eyes than if you weren't nearsighted. About 40% of the population has some degree of myopia or will develop it at some time in their lives.

Most commonly, myopia begins to appear gradually between the ages of 8 and 12, though it can exist at birth or start to develop as late as age 80. Myopia may be a nuisance but it is certainly not a disease; most nearsighted people have perfectly healthy eyes. Many "myopes" really like being able to see clearly up close without glasses. In fact, this ability can be a real advantage, especially after middle age.

Symptoms

The only symptom of myopia is blurred vision for distant objects. Eye fatigue, burning eyes, headache, and limited tolerance for reading occasionally accompany the myopia, but they are not symptoms of the myopia itself. When young children hold everything close to their face or sit very close to the television, it does not necessarily mean they are nearsighted -- they may simply like the way things look up close.

Understanding Myopia

In a properly focused camera, light focuses on the film at the back of the camera, and a sharp, in-focus picture is taken. In the same way, sharp vision depends on light rays coming to a focus on the retina (at the back of the eye). When light rays are not focused sharply on the retina, vision will be blurred, and we say that a refractive (optical) error exists. In myopia, the rays from distant objects focus in front of, rather than on, the retina. Myopia is like a camera that is in focus only for near objects; anything in the distance is out of focus.

What Causes Myopia?

In most cases, myopia is the result of a size variable, like height or foot size. A myopic eye is elongated, and its length doesn't coordinate with its optical power; in other words, its optical power is too strong for the eye. (You shouldn't think of nearsightedness as weak eyes.)

Research suggests that ordinary myopia and how fast it progresses during adolescence are determined by heredity: it tends to run in families. It is not caused by using your eyes "too much" (you never harm your eyes by using them). Some populations, the Inuit (eskimos), for example, have shown a statistical shift toward myopia when, over many years, they changed from outdoor activity to closer work indoors. This does not mean that doing close work will make a person myopic.

There are a few less common causes. Myopia that appears (or increases) in middle age may be a sign of a beginning cataract. In uncontrolled diabetes, myopia may appear suddenly and then change erratically from day to day. And rarely, a teenager may develop myopia from keratoconus, an unusual condition in which the cornea gradually becomes cone-shaped.

Why Does Myopia Get "Worse" as the Child Gets Older?

As children's bodies grow, so do their eyes, which may cause a gradual increase in myopia. And just as bodily growth can be in spurts, the changes in myopia may be similarly uneven. During adolescence, the change can be rather rapid and require a stronger eyeglass correction more than once a year, but when body growth slows or stops (usually by age 18), the myopia tends to stabilize.

There is normally no reason to worry about the frequent changes in lens correction during adolescence. There is almost never any real danger to eyesight, and vision can almost always be corrected to 20/20 or better with eyeglasses or contact lenses. (There is an extremely rare and serious type of myopia, "malignant progressive myopia," that leads to gradual structural damage to the eye. But this type is not related to nor does it develop from ordinary myopia.)

Lens Correction for Myopia

Eyeglasses or contact lenses provide a simple, effective way to attain clear vision. By optically reducing the excess power of the myopic eye, they make distance vision clear. The more nearsighted you are, the more you will want to wear your correction. Not wearing it, however, will not harm your eyes in any way.

Nearsighted children should be checked for glasses every year or so, and nearsighted adults every 2 to 3 years -- more frequently if you start having any symptoms that seem to be related to your eyes. For eye safety, impact resistant lenses are required by law for all eyeglasses. The safest ones, offering the best protection against eye injuries, are made of polycarbonate plastic.

Other Methods of Correction

There is some evidence that special contact lenses (in a procedure called orthokeratology), bifocal eyeglasses, or dilating eyedrops can slow the progression of myopia, but the effects are very minimal and temporary, and rarely worth the extra effort and cost. Treated or not, myopia almost always advances to a certain point and then stops changing.

Refractive surgery is an option for reducing your dependence on glasses or contacts. These surgical procedures are designed to permanently reduce the optical power of the cornea to achieve normal or near-normal focus. LASIK and PRK involve use of an excimer laser to reshape the cornea. Intacs are surgically implanted corneal ring segments that flatten the cornea; the effect is reversible by removing the rings. Refractive surgery is not appropriate for everyone, and it is not done on young eyes that are still growing. Before making a decision to have refractive surgery, you should learn all you can about it.

Taking Care of Your EyesExcerpted from Triad's Eye Care Notes 1989-2005 by Triad Publishing Co.

Patients: for more information about your eyes, see: Taking Care of Your Eyes: A Collection of the Patient Education Handouts Used by America's Leading Eye Doctors

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