Even though wearing eyeglasses is often just as much a matter of fashion as it is function, they are still primarily used to correct vision. Clear vision results from light rays being bent by your cornea and focused on the retina before sending the picture to your brain through the optic nerve.
People generally require corrective eyeglasses when this process is distorted or disrupted. There are several reasons this might happen, but here are a few of the most common.
Nearsightedness
If you're nearsighted, you can see things clearly when they're at close range but have trouble with objects that are farther away. Nearsightedness is also called 'myopia' and it's characterized by a lot of squinting at things that are in the distance.
Signs that your children may be nearsighted include squinting at the blackboard in school or always trying to sit closer to the television.
Farsightedness
Another common vision condition that requires eyeglasses is farsightedness, also known as 'hyperopia'. With farsightedness, you basically have the reverse condition of nearsightedness. Objects that you view from a distance look clear and in focus, but when you look at things up close you have issues.
This condition may seem illogical to some, but it is still quite real and problematic if you have it. With farsightedness, your cornea may have less than an optimal amount of curvature or your eyeball may be shorter than it needs to be.
Some of the symptoms of farsightedness include headache, burning eyes and eyestrain.
Astigmatism
Most people have probably heard of astigmatism, and although it sounds pretty serious it isn't so bad. Basically, it means that your vision is blurred up close and at a distance, like you have both myopia and hyperopia.
You can develop mild astigmatism at virtually any age, and sometimes your doctor won't even prescribe corrective eyeglasses. Serious cases of astigmatism are usually inherited and may result in a patient having to wear corrective lenses from a relatively early age.
Presbyopia
If the lens inside your eye has lost some of its elasticity, the condition is called presbyopia. This condition acts similarly to farsightedness, and it continues to worsen with age. Corrective eyeglasses will be prescribed when the condition is first diagnosed, and that prescription will likely have to be increased as the years go by. Like with farsightedness, someone with presbyopia may tend to hold books and other reading materials out at arm's length so they can see the words more clearly.
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