How to Read Contact Lens Scripts

The numbers on your contact lens prescription, or script, may look like a foreign language to you, but once you understand a few basic optical terms and abbreviations, you'll be able to decipher your script. Your eye doctor writes measurements and abbreviations on the prescription that the person who fulfills your order fully understands. Under the 2003 Fairness to Contact Lens Consumers Act, you're entitled to have the contact lens retailer of your choice fill your prescription, so it would be helpful for you to understand what your script says.

Instructions

• 1

  Look at each eye on your prescription. The right eye is written as OD, for Oculus Dexter, and the left eye is written as OS, for Oculus Sinister. Some doctors simply use a "R" and "L" for right and left but most eye care practitioners use OD and OS.

• 2

  Note the power for each eye, sometimes written as "PWR." This number is a measurement of your nearsightedness or farsightedness. In addition to power, your prescription may or may not contain a correction for astigmatism, an irregular shaped-cornea which, is very common. This number is written as cylinder or "Cyl" and will be followed by the Axis, a number between 0 and 180. Cylinder power can be as low as .25 or much higher, depending on the amount of astigmatism your prescription requires. The higher the number, the stronger the correction.

  Your prescription axis number is the location in the lens that corrects to compensate for the irregular corneal shape. Axis is written in degrees, between 0 and 180 degrees. If you think about a complete circle or the eye being 360 degrees, a lens prescription for axis is a horizontal line across the eye and the cylinder and axis correction for astigmatism falls within the 180 degrees on the horizontal line. The number corresponds to where the astigmatic power is placed on the axis.

• 3

  Check for the Base Curve, another important element of a contact lens prescription. The Base Curve, or "B.C.," describes the back curvature of your contact lens, so that the lens sits comfortably and properly on your eye. Base Curves are measured and prescribed in millimeters and can be anywhere from 8.0 to 10.0 millimeters.