Myopia (Nearsightedness)

August 18, 1999
Web posted at: 12:11 PM EDT (1611 GMT)

In this story: Description Risk Symptoms Treatment Prevention RELATEDS

From WebMD

DESCRIPTION

When you look at an object, light waves pass through the clear outer covering of the eye -- the cornea -- to reach the lens. The lens bends the waves and focuses them on the retina, which is located at the back of the eyeball. Myopia occurs when the eyeball is elongated rather than round or when the surface of the cornea is too steeply curved. These conditions cause the lens to focus images at a point in front of the retina. By the time the light makes its way to the retina, the image has become fuzzy.

RISK

Myopia tends to run in families. Most often it is the result of inherited variations in the shape of the eyeball. The condition usually first develops when a child is between the ages of 8 and 12. As the eye grows, a child's vision can change rapidly, requiring a stronger corrective prescription every few years. These changes tend to level off around age 18, when the eyeball reaches its full size.

A small number of myopia cases result from years of close-up vision work. Myopia that first appears in middle age can indicate cataracts. If nearsightedness comes on suddenly and seems to change daily, it could be the result of uncontrolled diabetes. In rare cases, myopia develops in adolescence as the result of keratoconus, a condition in which the cornea becomes cone-shaped.

SYMPTOMS

The primary symptom of myopia is the inability to see objects clearly at a distance. Burning eyes, headache, eye fatigue and difficulty reading are usually not associated with myopia.

TREATMENT

The tried-and-true solutions for myopia are corrective glasses and contact lenses. Most of the time, these devices can bring vision back to 20/20. The amount of time a person needs to wear corrective gear will depend on the severity of the myopia.

Several surgeries, collectively known as refractive eye surgery, are now available to correct myopia. Refractive eye surgery involves reshaping the cornea so that the image you see focuses directly on the retina rather than in front of it. In the pioneering form of this surgery, called radial keratotomy (RK), the surgeon makes spokelike slits in the cornea to flatten it. This procedure has been replaced largely by newer, laser-based techniques such as photorefractive keratotomy (PRK) and laser in situ keratomileusis (LASIK). PRK uses a computer-controlled laser to vaporize minute slices from the cornea's surface. LASIK, a more recent iteration of the laser technique, is now the most common optical-surgery procedure, accounting for approximately 90 percent of corrective eye surgeries. LASIK combines a cutting instrument that creates a hinged flap on the surface of the cornea with a laser that reshapes an area of the cornea under the flap. An even newer development in correcting myopia involves surgically implanting a thin, crescent-shaped piece of acrylic to flatten out the surface of the cornea.

PREVENTION

Since myopia is largely hereditary, there is little that can be done to prevent it. Research has failed to prove that eye exercises, eyedrops or other measures can slow or halt the progression of myopia.

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