If you go to an eye care professional for all of your optical needs, then reading your eyeglass prescription is something that you may never have to worry about. However, if you ever plan on trying to order a pair of eyeglasses online without visiting the optician's office it's imperative that you know how to properly read your prescription it you want to get a pair of glasses that you can see out of.

You prescription will often be delivered as a pair of numbers - one number under the Latin abbreviation of OS (your left eye) and the other under the Latin abbreviation OD (your right eye). The farther away either number is from zero in either direction (plus or minus) the worse your eyesight is and the more correcting your vision will need for you to be able to see clearly.

If the numbers in your prescription are in the positive it means that you are farsighted, or that you have problems with seeing things close to you; if the numbers are in the negative it means that you are nearsighted or that you have difficulty viewing objects that are far away.

If you suffer from astigmatism you'll see three numbers in your eye glasses prescription - the first of which will represent both of the numbers seen in a prescription of a person who doesn't have astigmatism, the second number will represent the severity if the astigmatism - the larger the number here the greater you are effected by the astigmatism. The third number in the prescription of a person who suffers from astigmatism will be between zero and one hundred and eighty and this number reveals the location of the astigmatism. For proper corrective treatment of astigmatism, the technician making your lenses needs to know the location of the astigmatism in degrees as well as the level of severity.

Each of the numbers that you see in your eyeglass prescription is crucial to the final result, the numbers may be whole numbers or they may be fractional (like 1.25, representing one and one quarter) and the exact number is required for you to be able to see clearly. The numbers represent diopters which is the unit of vision correction from which your lenses will be manufactured. If you are off by even a fraction of a point when relating the information of your diopters, your glasses may not be as precise as they need to be to properly correct your vision. When relating all of the numbers and symbols of your eyeglass prescription for an order it's imperative that you be precise or you will receive a pair of glasses that won't properly correct your problem.

There are other considerations when contemplating ordering prescription glasses online that don't necessarily have to do with your prescription itself, but that could seriously affect the corrective properties of your glasses. The most common number not represented in your prescription that you'll need to know when ordering glasses online is the distance between your pupils, or your PD. There's a good chance that your PD will be imprinted somewhere on your old glasses, if you've still got them - if you don't the number isn't all that difficult to get. You'll need a ruler that measures in millimeters and a mirror. All you do to get you PD is to look straight ahead into the mirror and hold your ruler directly below your eyes to measure the distance between the centers of your pupils. The most common distance for a PD is between 58 and 70 mm, so if your distance is either well under 58 or well over 70, you might want to measure again.

Reading your prescription and ordering glasses without visiting the optician is certainly possible, but if you have any questions about what you're reading it's highly advisable to visit your eye care professional to be certain that you get it right - eyeglasses are expensive and you certainly won't be able to return a custom pair, so make sure you get everything right before you make anything final.