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.
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.
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:
- 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.
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.