How to Read an Rx for Glasses

At first, your eyeglass prescription may look like Greek. It's close-prescriptions use Latin abbreviations and a shorthand notation particular to optometry. You have the right to obtain your eyeglass prescription, allowing you to buy glasses online or from a retail store of your choosing. It only takes a few minutes to understand your prescription.

Things You'll Need

• Your eyeglass prescription

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Instructions

• 1

  Look at the headings of OS and OD. These are Latin abbreviations for oculus sinister (left eye) and oculus dextrus (right eye). Sometimes the abbreviation OU is used; this indicates both eyes. Numbers next to the headings tell how nearsighted or farsighted you are. The further away from zero, the worse your eyes are. A negative sign before the number indicates nearsightedness, and a plus sign indicates farsightedness. These numbers indicate diopters, the unit which measures the focusing power of the lens you need.

• 2

  The first number, under "SPH "refers to the spherical portion, which is the measure of how nearsighted or farsighted you are. Different SPHs in each eye are not uncommon.

• 3

  The next number under "CYL" refers to the cylinder, or astigmatism. Astigmatism, in which vision is blurred due to an irregularly curved cornea, is a very common condition in people who need glasses. If no astigmatism is present, the letters DS or SPH are used to indicate no correction is needed for astigmatism. The number may be positive or negative and also measures in diopters.

• 4

  The number under "AXIS" indicates the astigmatism in degrees from the horizontal axis. Axis ranges anywhere from 0 to 180. Sometimes a number follows under "PRISM", indicating prism correction.There may be more than one number for prism.

• 5

  The last number under "ADD" indicates the amount of near reading strength needed.