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How Do I Read My Glasses Prescription?

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Ever wondered what all the letters and numbers in your glasses prescription mean? Wish you could understand and read your prescription?

Here’s a quick guide from our Woodcliff Lake eye care team to help you become an expert at reading your prescription!

Your Glasses Prescription

If you take a look at your prescription, you’ll notice a few numbers listed under different labels: OS and OD, or OU.

What do these labels mean?

– OS: oculus sinister, referring to the left eye

– OD: oculus dextrus, for the right eye

– OU: oculus uterque, both eyes.

Although these Latin terms are still widely in use, some eye care offices are beginning to move toward using English-based abbreviations: RE, for the right eye and LE for the left one.

How to Read Nearsighted and Farsighted Prescriptions

When reading prescriptions that correct for nearsightedness or farsightedness:

  • The further from “0” the number is, the stronger the prescription
  • + refers to a farsighted prescription
  • – refers to a nearsighted prescription

As examples:

  • -1.00 would represent very slight nearsightedness, whereas -6.00 or more would represent more severe nearsightedness.

The same applies to farsightedness

  • +1.00 would be slight farsightednees, and +6.00 or more would be more severe farsightedness.

What About My Astigmatism Prescription?

Because astigmatism creates a more football shaped cornea, rather than a round one, there are extra items to consider. Your prescription will therefore lookquite different.

Here are the elements of an astigmatism prescription:

  • SPH: measures how nearsighted or farsighted you are.
  • C or CYL: shows how astigmatic your eyes are. The number can be negative or positive, and the bigger it is, the stronger your astigmatism.
  • Axis: This number will be between 0 and 180 degrees, and tells your optician where exactly the curvature in your cornea is, and how it’s positioned.

What Other Measurements Might Be In My Lens Prescription?

ADD: This represents the additional correction needed for presbyopia. It measures your need for bifocal or progressive lenses, and is a way of adding two different prescriptions together, to address the issues causes by presbyopia at all visual distances.

PD (Pupillary distance): Refers to the distance, in millimeters, between both pupils in the eyes. This helps our Woodcliff Lake optical team figure out exactly where you’ll be looking through your lenses for different visual tasks, and helps determine frames that are right for you, as well as the best way to construct your lenses to ensure the clearest most comfortable vision.

Want to know more about how to read your eyeglass prescription. Talk to our Woodcliff Lake eye doctors at James Tracey Eye Care today!


Are contact lens prescriptions the same as glasses prescriptions?

No. Glasses and contact lens prescriptions are completely different. This is because glasses are placed slightly in front of the eye, while contacts rest on the eye itself. This creates a difference in how they reflect light into the eye and how they need to be constructed to properly correct your vision.

What glasses prescription represents legal blindness?

Legal blindness is defined by a person either having less than 20 degrees of vision as determined in a visual field test, or visual acuity of 20/200. This means that this person can only see clearly from 20 feet what a person with 20/20 vision could see clearly from 200 feet. This is the same as a prescription of -2.5.