What is myopia?
When you are nearsighted (myopic), you are able to see clearly up close, but everything in the distance is blurred. (The more nearsighted you are, the closer you can see clearly and the greater the distance blur.) When a child cannot see the blackboard clearly from the back of the classroom or when an adult cannot read road signs, chances are that he or she is nearsighted. Myopia increases and is more apparent in the dark, so that street signs you see easily during the day may appear blurred at night. Approximately 40 percent of the population has myopia or will develop it at some time in their lives. Myopia usually begins gradually between the ages of 8 and 12, though it can exist at birth or start as late as age 80. There are no special precautions that you need to know about. Continued use of the eyes will not damage them. Nearsighted children should be checked for glasses every year or so, and nearsighted adults every 2 to 3 years --more frequently if any symptoms occur that are related to the eyes. Myopia may be a nuisance but it is certainly not a disease; it is possible (even likely) to be very nearsighted and still have perfectly healthy eyes. In fact, some "myopes" think that seeing things so close-up is a real advantage.
What are the symptoms?
The only symptom of myopia is the blurred vision for distance. The fact that young children tend to hold everything close to their face or sit very close to the television does not necessarily mean they are nearsighted. All children tend to do this because they see so much better up close. Eye fatigue, burning eyes, headache, and limited tolerance for reading are not usually symptoms of myopia.
What causes myopia?
Most myopia is the result of a normal physical variation in length of the eye (like tallness or shortness). The elongated myopic eyeball has more optical power than the eye needs (in other words, the eye is "stronger," not weaker, than other eyes). Research suggests that typical, run-of-the-mill myopia and its rate of progression is inherited and tends to run in families. A very small proportion may be related to using the eyes for close work over many years. There are a few less common causes. Myopia that starts in middle age may be a sign of a beginning cataract. In uncontrolled cases of diabetes, myopia may occur suddenly and then change erratically from day to day. Rarely, a teenager may develop myopia from keratoconus, an unusual condition in which the cornea becomes cone-shaped. Extremely rare is a type called malignant progressive myopia, a serious condition that does not develop from ordinary myopia.
Why does myopia get "worse" as the child gets older?
Children tend to have a gradual increase in myopia as their bodies (and eyes) grow. The excess optical power created by eye growth tends to occur unevenly. During adolescence, the change can be rather rapid and require new, thicker eye-glasses more than once a year, but when full ocular maturity is reached and growth is completed (usually by age 18), myopia progression tends to slow or stop. There is normally no reason to worry about the constant changes. It is almost never a real danger to eyesight and vision can almost always be corrected to 20/20 with eyeglasses or contact lenses. There is little scientific evidence that eye exercises, bifocals, contact lenses, or dilating eyedrops can significantly affect or slow the course of myopia; therefore few doctors recommend any of them. Myopia almost always reaches a certain point and stops naturally, with or without efforts to treat it.
Is there a correction for myopia?
Fortunately, optical correction for ordinary myopia is simple and effective. Eyeglasses or contact lenses can be custom-made to perfectly compensate for the excess optical power. Once you have corrective glasses or contacts, it is up to you how much time you wear them. The decision will be based on your own need for clear distance vision (as long as the correction is in front of your eyes, light rays entering the eyes will be properly focused on the retinas). The more nearsighted you are, the more you will probably want to wear your correction. Not wearing it will not harm your eyes. Impact resistant lenses are required by law for all eyeglasses, but the safest ones for active children are polycarbonate plastic lenses. These offer the best possible protection against eye injuries.