Understanding Your Eye Prescription

As soon as you leave the eye doctor’s office, you look at the prescription. Although it is simple, the eye prescription may seem like a complicated series of abbreviations and numbers. The code helps your eyeglass manufacturer to know if you are farsighted or nearsighted. Moreover, it also helps to know whether you have presbyopia or astigmatism. Your prescription has a number for every category that needs attention. This number indicates diopters, which is a unit for measuring the lens power required to correct the vision.

It is interesting to know that the further from zero the numbers are, the worse your eyesight can be. A minus or plus sign implies what kind of sight problem you suffer from. A plus sign indicates farsightedness. In case of a minus, you are nearsighted.

Understanding the Abbreviations

Several different terms and abbreviations are mentioned in the eye prescription. This information is generally in the form of a grid with a few abbreviations, such as PRISM, AXIS, SPH and CYL written across the top row, whereas, abbreviations such as O.U., O.D, O.S. and ADD are written in the left column.

Let’s see what each of these means:

  • ADD – Added magnifying power in the bottom of a multi-focal lens for correcting presbyopia that is the inability to focus on near objects
  • D. – Oculus dexter
  • S. – Oculus sinister
  • U. – Oculus uterque

These are the Latin terms for right eye, left eye, and both eyes.

  • SPH (or Sphere) signifies the prescription power. The ADD indicates the power of the lens required to rectify your eyesight problems.
  • CYL (or Cylinder) represents astigmatism. This means an abnormally shaped cornea and causes distorted or blurred vision. It also spells out the lens strength required to fix it.
  • AXIS describes the direction and degree of your astigmatism.
  • PRISM reveals the amount of prismatic power required for correcting eye alignments of different kinds. However, only a few eyeglass prescriptions may have this information.

When you learn to read your eyeglass prescription, it is convenient to comprehend what exactly your prescription conveys about your vision. It is suggested you get your eyes tested every year to guarantee your prescription is up to date.

The 20/20 Scale

The sharpness of a person’s vision can be measured with the 20/20 scale. For this, an eye doctor places a chart that is 20 feet away. You have to read the letters starting from the large E at the top. This series of alphabets continues down ten rows. Anybody who has normal 20/20 vision will read the first 8 rows from twenty feet. If a person has 20/50 vision, it means he can see at 20 feet away what a regular person views at 50 feet with normal vision, and so on.

The next time you get your eye prescription, you can easily figure out what needs to be fixed and how much strength of the lens will be.

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