What Do The Numbers On A Contacts Prescription Mean?

11 January 2016
 Categories: , Blog


Once you have your prescription for contacts, there are several places from which you can choose to purchase them. To make the best decision about your contacts, it is ideal to know the basics of the information on the prescription. Before ordering your new contacts, here is what you need to know about your prescription.

What Do the Numbers Mean?

The numbers on your contacts prescription might look difficult to understand, but there is a simple explanation for each one. The numbers in the OD and OS categories might be different from each other. The OD refers to the right eye and the OS refers to the left eye.

The first number listed is the refractive power, or PWR. The number refers to the amount of correction that is needed for your distance vision to reach an acceptable level. Sometimes, there is a plus or minus sign before the number. The plus sign indicates that the correction is for farsightedness. The minus sign is for nearsightedness.

The base curve, or BC, refers to the curve of your eye. A low number means a steeper curve of the cornea.

The distance, or DIA, on the prescription refers to the distance from edge to edge on your contact. The distance is one of the most important. It helps to determine how the contacts will sit on your eyes.

If you have an astigmatism, the cylinder, or CYL, section of the prescription should be filled out. The cylinder indicates the level of correction that is needed for the more nearsighted or farsighted vision of your eye. The axis details how the cylinder power should be centered on your cornea to compensate for the astigmatism.

If you require bifocal contacts, the added magnifying power, or ADD, denotes which portion of the contact needs magnification.

How Long Does Your Prescription Last?

The minimum time limit for a contacts prescription varies by state. It is either one or two years. Once the expiration for the prescription is reached, you must be re-examined to get a new one. You cannot purchase replacement contacts until the examination is completed.

Failing to get a new prescription can be damaging to your eyes. Prolonged usages of contacts can result in discomfort, infection, and distorted vision.

Consult with an eye doctor like All About Eyes for further details about your prescription. The doctor can not only help you understand the prescription, but also with ordering the contacts to ensure that you get lenses that properly fit. 


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