ANSWERS: 1
  • As of 2004 all eye care providers in the United States are required by law to furnish a copy of your contact lens prescription. This is meant to allow you to purchase your lenses from any retailer, but if you want to understand the prescription the combination of numbers and abbreviations can seem cryptic.

    Refractive Power

    The refractive power is the number shown after the abbreviation "PWR." This number describes the amount of correction needed. A positive number indicates farsighted vision while a negative number indicates nearsighted vision.

    Base Curve

    The base curve measurement will appear in millimeters and is used to ensure that the curve of the contact matches the curve of the eyeball. The abbreviation for base curve is "BC."

    Diameter

    The number after the abbreviation "DIA" is the diameter, or distance from one side to the other, of the contact lens. The diameter is expressed in millimeters and affects the comfort level of the contact.

    Cylinder

    If the contact lenses correct astigmatism there will be a cylinder number. This number comes after the abbreviation "CYL" and shows how much astigmatism correction the lenses provide. It may be a positive or negative number.

    Axis

    The axis is another number related to astigmatism. It is a number of degrees, always positive, and shows the orientation of the cylinder within the lens, which corrects the astigmatism.

    "ADD" Number

    The number following the word "ADD" is the refractive power for an additional lens. This is used in bifocal situations.

    Source:

    All About Vision: Understanding Your Contact Lens Prescription

    More Information:

    ACLens.com: How to Read Your Contact Lens Prescription

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