The simple answer is, visit an Optometrist (or as Optometrists used to be known, Ophthalmic Opticians). The question to be asked is – what are the symptoms that you may be experiencing that would make you visit the Optometrist to find out if you need glasses.
There are different symptoms associated with different ocular problems. It is important to recognize them and to become sensitive to the frequency. None of these symptoms will make you vision worse (or better), but realizing that they apply to you should motivate you to have your eyes tested by a professional – you will enjoy a better lifestyles afterwards.
Short sightedness (myopia) causes blurred vision when viewing objects in the distance. You might not be the first person to notice that you have a problem. You may be subconsciously screwing your eyelids up when viewing things. screwing the eyes up creates a horizontal slit in your vision which can reduce the effect of myopia.
Long sightedness (Hypermetropia or hyperopia for short) can cause blurred vision for reading but is more likely in the early stages to cause a strain or headaches for close tasks, particularly on computers. It can also cause strain or headaches when viewing television.
Presbyopia can easily be spotted in people over 45. They tend to hold reading material further away or stand closer to light to view small print. It is caused by an inability of the eye to focus close up due to stiffening of the crystalline lens in the eye.