Understanding Your Eye Prescription


When you’re sick and visit your doctor, it is usually easy to understand the prescription you receive. Regardless of whether your physician writes legibly, you are likely to know what medication was prescribed. But when you are handed an eye prescription, does it ever make any sense? All those numbers, letters and signs can be confusing. The following list is a useful guide on eye prescription meanings and how to read an eye prescription.

How to Read Eye Prescriptions

  • OD and OS: These abbreviations on your eye prescription are short for the Latin terms oculus dextrose (right eye) and oculus sinister (left eye). At times, you may see OU, this means oculus units or both eyes. It is standard practice to use Latin abbreviations for prescription eyeglasses, but more modern doctors are now using RE for the right eye and LE for the left.
  • Sphere: These “D” measurements are diopters. They represent how much lens power is necessary to correct vision. The higher the number, the more correction that is needed. If the number is preceded by a plus sign, that indicates farsightedness. A minus sign before the number means nearsightedness.
  • Cylinder: This number represent the degree of astigmatism in the eyes. The cylinder figure is usually preceded by a minus sign. If the column is completely blank, no astigmatism is present, or it is not severe enough to warrant an eye prescription.
  • Axis: This number displays where the astigmatism is in the eye. It describes the direction so the doctor can position the cylindrical power in the lenses. This only needed for astigmatism. These numbers are measured in degrees of angle ranging from 1 -180. If no cylinder section is present on the eye prescription, there is no axis number. It is a spherical eye prescription.
  • Prism: These numbers represent the level of prismatic power needed to correct alignment problems. Very few eye prescriptions will include a prism, the need to correct eye alignment is very uncommon.
  • Add: This is additional magnifying power for presbyopia vision correction. This number is always a plus, even if it isn’t preceded by a plus sign. It is usually the same for both eyes.
  • PD: Pupillary distance, the area between the middle of both pupils. This number should remain the same once a person reaches adulthood. This measurement is an important factor when it comes to proper fit, comfort, and performance of prescription eyeglasses.