We all know we need a doctor’s prescription in order to purchase eyeglasses. A prescription is even more important for contact lenses because not only do we need to know the strength of the optical correction, but we must know what material would be best, as well as the shape and size of the lens. If you don’t have a proper prescription, your vision will be affected, or damage to delicate eye tissue could result from an improper fit. It’s important to visit your eye care professional for regular eye exams and contact lens fittings to maintain the health of your eyes.

Reading and understanding a contact lens prescription is a bit more difficult than a prescription for eyeglasses. There is more information contained in a contact lens prescription, including important measurements that wouldn’t be needed for eyeglasses. Let’s take a look at some of the standard terms, abbreviations and measurements eye care professionals use for a contact lens prescription.

Power: the amount of correction needed to bring your vision to 20/20. A negative number means the prescription is for myopia (nearsightedness); a + means the prescription is for hyperopia (farsightedness).

BC or Base Curve: the curvature of the contact lens needed to match or fit over your cornea.

Diameter: a measurement of the width of the lens from one side to the other through the middle. This is an important measurement because it determines where the edges of the contact lens will rest on your eye. An incorrect measurement can result in irritation and/or abrasion to the eye.

Axis: a measurement that is used if you need contact lenses for astigmatism.

Add: refers to the amount of correction you need for close-up viewing or reading-this would only be used for those who need bifocal contact lenses.

Brand: in the U. S. the prescription must always include the brand.

In addition, your contact lens prescription might specify how often your contact lenses should be replaced (daily, weekly, etc.). Your eye care professional knows which is best for your eyes and lifestyle.
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