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Myopia

Nearsightedness

Myopia (also called nearsightedness), is when objects close up appear clearly, but get blurry as they get farther away. Myopia is a very common vision condition affecting nearly 30 percent of the US population. Some research supports the theory that nearsightedness is hereditary. There is also growing evidence that it is influenced by the visual stress of too much close work.

Overview

What is myopia (nearsightedness)?

Nearsightedness occurs if the eyeball is too long or the cornea, the clear front cover of the eye, has too much curvature. As a result, the light entering the eye isn’t focused correctly and distant objects look blurred. In this situation, instead of images focusing directly on the retina (the light-sensitive part of the eye), they focus just in front of it. As a result, the light entering the eye isn’t focused correctly and distant objects look blurred.

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Causes

What causes myopia (nearsightedness)?

The exact cause of nearsightedness is unknown, but three factors may be primarily responsible for its development:

  • Heredity
  • Visual stress
  • Environmental factors

Heredity

There is significant evidence that many people inherit nearsightedness, or at least the tendency to develop nearsightedness. If one or both parents are nearsighted, there is an increased chance their children will be nearsighted.

Visual stress

Even though the tendency to develop nearsightedness may be inherited, its actual development may be affected by how a person uses his or her eyes. Individuals who spend considerable time reading, working at a computer or doing other intense close visual work may be more likely to develop nearsightedness.

Nearsightedness may also occur due to environmental factors, such as doing a lot of near vision work like reading and writing. Time spent outside is also a factor—increased outdoor time is an important (and modifiable) environmental factor that protects young children from myopia.
In simple myopia, the eyes are healthy and easily corrected by glasses or contact lenses.
However, a high amount of myopia can increase the risk of retinal tear or detachment.
Severe ( degenerative ) myopia is a medical condition that may cause vision loss which is not fully correctable to 20/20.

Symptoms

What are the symptoms of myopia (nearsightedness)?

A common sign of nearsightedness is difficulty seeing distant objects clearly, like a movie or TV screen or the chalkboard in school. You may also notice:

  • Headaches
  • Squinting
  • Eye strain
  • Eye fatigue when you try to see objects more than a few feet away

Generally, nearsightedness first occurs in school-age children. Because the eye continues to grow during childhood, it typically progresses until about age 20. However, symptoms of nearsightedness may also be a sign of variations in blood sugar levels in persons with diabetes or an early indication of a developing cataract.

Diagnosis

How is myopia (nearsightedness) diagnosed?

Testing for nearsightedness may use several procedures in order to measure how the eyes focus light and to determine the power of any optical lenses needed to correct the reduced vision. If you suspect you might have myopia, make an appointment with your doctor to have some testing done.

Visual Acuity Testing

As part of the testing, you may be asked to identify letters on a distance chart. This test measures visual acuity, which is written in a fraction—you may have heard of someone having “20/20 vision.” The top number is the standard distance at which testing is performed—always 20 feet. The bottom number varies, and it indicates the smallest letter size a person can read. A person with 20/40 visual acuity would have to get within 20 feet to identify a letter that could be seen clearly from 40 feet away in a “normal” eye. While 20/20 is the normal distance visual acuity, many people have 20/15 vision, which is even better.

Phoropter and Retinoscope Tests

Using an instrument called a phoropter, an optometrist places a series of lenses in front of your eyes and measures how they focus light using a hand-held, lighted instrument called a retinoscope. The doctor may choose to use an automated instrument that automatically evaluates the focusing power of the eye. The power is then refined by the patient’s responses to determine the lenses that allow the clearest vision.

Will I Need Eyedrops?

Testing may be done without the use of eye drops to determine how the eyes respond under normal seeing conditions. In some cases, such as for patients who can’t respond verbally or when some of the eyes’ focusing power may be hidden, eye drops may be used. They temporarily keep the eyes from changing focus while testing is performed.

A group of children huddle together in grass.

Treatment & Prevention

How is myopia (nearsightedness) treated?

Persons with nearsightedness have several options available to regain clear distance vision. They include:

  • Eyeglasses
  • Contact lenses
  • Laser and other refractive surgery procedures
  • Vision therapy for persons with stress-related nearsightedness

Eyeglasses

    Eyeglasses are the primary choice of correction for persons with nearsightedness. Generally, myopia is treated with prescribed single-vision lenses, but for patients over age 40 or those with myopia caused by near vision work, a multifocal lens may be needed. Eyeglasses are no longer just a medical device that provides needed vision correction; they can also be a fashion statement. They are available in a wide variety of sizes, shapes, colors and materials that not only correct for vision problems but also may enhance their appearance.

Contact Lenses

    For some individuals, contact lenses can offer better vision than eyeglasses. They may provide clearer vision and a wider field of view. However, since contact lenses are worn directly on the eyes, they require regular cleaning and care to safeguard eye health.

PRK and LASIK

    Nearsightedness can also be corrected by reshaping the cornea using a laser beam of light. Two commonly used procedures are photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). In these procedures, lasers are used to remove tissue from the eye in order to change the eye’s shape and refocus light entering the eye. With both procedures, the amount of nearsightedness that PRK or LASIK can correct is limited by the amount of tissue that can be removed in a safe manner.

Intraocular Lenses

    People who are highly nearsighted or whose corneas are too thin to allow the use of laser procedures now have another option. They may be able to have their nearsightedness surgically corrected by implanting small lenses in their eyes. These intraocular lenses look like small contact lenses and they provide the needed optical correction directly inside the eye.

Vision Therapy

    Vision therapy is an option for people whose blurred distance vision is caused by a spasm of the muscles which control eye focusing. Various eye exercises can be used to improve poor eye focusing ability and regain clear distance vision.

Think you may have myopia?