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Myopia (Nearsightedness)

By Judith Lee and Gretchyn Bailey; reviewed by Vance Thompson, MD; Flash illustration by Stephen Bagi

Nearsightedness, or myopia, is a vision problem experienced by up to about one-third of the population. In fact, a recent study* found that myopia is more common among Americans now than it was 30 years ago.

Nearsighted people have difficulty reading highway signs and seeing other objects at a distance, but can see for up-close tasks such as reading or sewing.

Myopia Symptoms and Signs

Nearsighted people often have headaches or eye strain and might squint or feel fatigued when driving or playing sports. If you experience these symptoms while wearing your glasses or contact lenses, you may need a comprehensive eye examination as well as a new prescription.

What Causes Myopia?

Myopia occurs when the eyeball is slightly longer than usual from front to back. This causes light rays to focus at a point in front of the retina, rather than directly on its surface.

Nearsightedness runs in families and usually appears in childhood. This vision problem may stabilize at a certain point, although sometimes it worsens with age. This is known as myopic creep.

Myopia Treatment

Nearsightedness may be corrected with glasses, contact lenses or eye surgery. Depending on your vision problem, you may need to wear your glasses or contact lenses all the time or only when you need distance vision, like driving, seeing a chalkboard or watching a movie. If you're nearsighted, your prescription is a negative number. The higher the numeral, the stronger your lenses will be.

Refractive surgery can reduce or even eliminate your need for glasses or contacts. The most common procedures are performed with an excimer laser.

• In PRK the laser removes a layer of corneal tissue, which flattens the cornea and allows light rays to focus closer to or even on the retina.
• In LASIK — the most common refractive procedure — a flap is cut through the top of the cornea, a laser removes some corneal tissue, and then the flap is dropped back into place.

Then there's orthokeratology, a non-surgical procedure where you wear special contact lenses that slowly reshape the cornea over time to correct your myopia. When the lenses are removed, the cornea temporarily retains the new shape, so you can see clearly without the lenses.

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With orthokeratology or corneal refractive therapy (CRT), an orthokeratology-like procedure approved by the FDA in 2002, you wear cornea-shaping lenses at night, so you have daytime vision without contacts or glasses.

Implantable lenses known as phakic IOLs are a newer surgical option for correcting nearsightedness, particularly in more extreme cases that may be unsuitable for LASIK or other vision correction surgery.

Phakic IOLs work like contact lenses, except they are surgically placed within the eye and typically are permanent, which means no maintenance is needed. Unlike IOLs used in cataract surgery, phakic IOLs do not replace the eye's natural lens, which is left intact.

A Rarer Condition: Pathologic Myopia

Nearsightedness usually is a mildly debilitating condition that is easily correctible, in most instances with glasses, contacts or vision surgery. But there are rare cases where the myopia is so severe it is considered pathologic.

Pathologic, or degenerative, myopia typically develops by age 12 in those with an extraordinarily elongated eyeball. About two percent of Americans are afflicted.

The stretching of the eyeball worsens with age and can result in a progressive and severe loss of vision. Compounding the problem in many cases is an abnormal growth of new blood vessels (neovascularization) beneath the macula.

Until recently, little could be done to stop the condition from advancing. Eye care practitioners could simply prescribe the strongest possible glasses and hope for the best. Laser treatment is unreliable; in many cases it only makes matters worse.

However, in 2001, the FDA approved the injectable photosensitive drug Visudyne (verteporfin) along with non-thermal laser application as a treatment for the neovascularization in pathologic myopia. In clinical trials, this treatment known as photodynamic therapy or PDT stabilized or improved vision in 72 percent of patients after one year, versus 44 percent on placebo.

Recent studies also demonstrate effectiveness of this therapy. Japanese research reported in the March 2008 edition of American Journal of Ophthalmology showed that PDT helped stabilize damage from neovascularization, which otherwise likely would have progressed in this form of pathologic myopia.

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*Increased prevalence of myopia in the United States between 1971-1972 and 1999-2004. Archives of Ophthalmology. December 2009.

[Page updated January 2010]