When the eye’s optical power and length do not match perfectly, vision will not be in focus. If your distance vision is blurry, but close-up objects are clear, you are nearsighted (myopic). You are a high myope (very nearsighted) if you have to hold object very close to your eyes to see them clearly.
If you are farsighted (hyperopic), you can see clearly in the distance but only by expending more focusing effort than normal, and even more effort for up close. You may not even be aware of the added effort, but over a period of time it can cause eyestrain and headaches. Farsightedness may not become a problem until you get older. (How much older depends on the amount of farsightedness). Actual difficulty with focusing up close, which becomes evident in everyone by age 45 or so, will probably be noticeable earlier, perhaps when you are about 35, or even sooner if you have a very large hyperopic error.
Having a refractive error does not mean that you eyes are ‘bad’ or weak’. Just as some people are tall and others are short, some have small hands and others have large feet, those having long eyeballs tend to be nearsighted and those with short eyeballs, farsighted.
– Drs. Fine, Hoffman & Packer http://www.finemd.com/pdfs/refractive_errors.pdf
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CNIB – Seeing beyond vision loss