How to Read Contact Lens Prescriptions

A contact lens prescription varies slightly from an eyeglass prescription. Normally, the prescription is valid for one year. Because of the way they are worn, the power of contact lenses differs from that of glasses. The technical term used to describe the lens optics being closer to the eyes is "effectivity." Contact lens prescriptions also contain additional information related to lens measurements. The prescription lists information in a right eye to left eye format. Base curve measurements will differ by contact brand. A new prescription will be needed if you change manufacturers. The prescription may include instructions on how long you can wear the lenses for a given time. The prescription layout may vary, but all terms, abbreviations, and measurements are universal.

Things You'll Need

• Contact lens prescription

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Instructions

How to read Contact Lens Prescriptions

• 1

  OS (Oculus Sinister) refers to the prescription for the left eye. OD (Oculus Dexter) refers to the prescription for the right eye. OU (Oculus Uterque) means the prescription can be filled for either eye.

• 2

  PWR (Power) is the amount of correction needed measured in dioptres. The range is from -20.00 to +20.00. A negative number means nearsighted or myopic; the positive number indicates farsighted or hyperopic.

• 3

  BC (Base Curve) measures the size of the clear covering needed for an eye. The range is from 8.0 to 10.0 millimeters.

• 4

  DIA (Diameter) refers to the width of the lens. The range is from 13.0 to 15.0 millimeters.

• 5

  BRAND is the manufacturer's name of a particular lens

• 6

  COLOR (optional) refers to a specific type of lens. Visibility tints are prescription lenses that do not alter eye color. The tinted lenses are easily identifiable are stored in cases. Enhancers slightly change the natural eye color. Opaque contacts will lighten, darken, or completely alter natural eye color.

• 7

  ADD (Add power) is an additional correction for reading or close up viewing specific to bifocal contact lenses. The power is always assumed as positive, even if not displayed on the prescription

• 8

  CYL (Cylinder) is a measurement used for Toric lenses, which are worn by people with an astigmatism. The ranges is -0.75 to -10.00 and is measured in dioptres.

• 9

  AXIS is another measurement used for Toric lenses. The range is 0 to 180. It measures how many degrees the contact lens must rotate to compensate for oval instead of round-shaped (astigmatic) eyes.