Encyclopedia - Myopia (Nearsightedness)

How do your eyes function?
How is myopia corrected?

Myopia is the ability of the eye to clearly see objects that are up close, but not far away. A nearsighted person can usually see well to read, but has trouble with distance vision, such as that used in driving. This is a common refractive eye condition created when the eyeball is more elongated than normal from front to back, or the cornea is too steep or dome-shaped. Myopia is an inherited condition that affects about one person in five.

How do your eyes function?

The eye functions much like a camera with two lenses. The first lens is the cornea, a clear membrane that covers the front of the eye. The second lens is the eye's natural crystalline lens, which is located behind the pupil. The cornea is responsible for about 70 percent of the eye's focusing power, while the natural lens "fine-tunes" the image before it is focused on the retina at the back of the eye (See Anatomy of the Eye). The retina works like the film in a camera, receiving light images and sending them via the optic nerve to the brain. If both lenses are working properly, the image is focused precisely on the surface of the retina.

How is myopia corrected?

The usual treatment for myopia is prescription eyeglasses with concave (inwardly curved) lenses or contact lenses that counteract the distortion created by corneas that are too outwardly curved in shape. A concave lens moves the image of a distant object backward onto the retina, thereby bringing it into proper focus.

Refractive eye surgery, which flattens the cornea, has also become a popular option for the correction of nearsightedness in recent years. The most popular of those procedures is Laser In-Situ Keratomileusis (LASIK), which uses an Excimer laser to reshape the cornea, often eliminating the need for corrective lenses. Another option that is becoming popular is Intrastromal Corneal Ring Segments (ICRSs), tiny plastic arcs that are implanted in the peripheral area of the cornea, causing the center of the cornea to flatten. These segments can be removed and/or replaced if needed. Refractive eye surgery is usually not recommended for people under 18 years of age.