How Do I Read an Rx for Sunglasses?

Reading a prescription for sunglasses is the same as reading a prescription for regular eyeglasses. On a typical prescription, you will see a number of different abbreviations that represent specifics relating to your eye condition and vision limitations. In addition, you will find some numbers and a plus sign or a negative sign next to those numbers, indicating farsighted (vision limitations up close) or nearsighted (vision limitation at a distance). Your prescription may have two numbers or three, depending whether you have astigmatism, an irregular curvature of the cornea. Your prescription lets the manufacturer of your lenses know exactly how to fashion them so they help correct your vision.

Instructions

• 1

  Pick up your prescription and look at it. You will see two or three numbers, with a plus sign or a negative sign in front of the first two numbers. The first two headings are "OS" and "OD." OS refers to your left eye and OD refers to your right eye. You might see the heading "OU" to refer to both eyes.

• 2

  Read the numbers under the OS and OD headings. The numbers themselves represent diopters, or the degree of focus for your lenses. If you see a plus sign in front of the number, this means you are farsighted and if your see a negative sign, this means you are near sighted. For example, if you have a prescription that reads OS +1.50 OD -2.00, this means you have 1.5 diopter of farsightedness in the left eye and 2 diopter or nearsightedness in the right eye.

• 3

  Check to see if there is a third number. This number will refer to astigmatism or the irregular curvature of the cornea. The formula for recording a prescription with astigmatism is S x C x Axis. The S stands for spherical, referring to your degree of near- or farsightedness, the C stands for cylinder, measuring the degree of astigmatism. The axis is the angle of degree, or the orientation of the cylinder power required to counter the astigmatism, which is the irregular shape of the cornea. An example of a prescription for someone with astigmatism might read OS -3.00 +2.50 x 110 and OD -2.00 +1.50 x 80. This translates to 3 diopters of nearsightedness with 2.5 diopters of astigmatism and an axis of 110 degrees in the left eye, while the second portion reads to 2 diopters of nearsightedness with 1.5 diopters of astigmatism and an axis of 80 degrees in the right eye.

• 4

  Look at the next line on your prescription and your will also see a number next to the heading "PD," which stands for Pupillary Distance. This heading records the measurement between the center of the pupil in one eye and the center of the pupil in the other eye and is a requirement for all eyeglass prescriptions. You should never attempt to measure this distance yourself, as sometimes more than one number is required due to vision deficiencies. The include your pupils being off center due to your eye condition.