April 9, 2019 Eye Associates

How to Read Your Eyeglass Prescription

You just had your annual eye exam and have given your eye prescription to an optician so you can pick out the perfect pair of new eyeglasses.

You may know in general whether you’re nearsighted or farsighted, but what exactly do all those machines used in your eye exam measure? And what do all the numbers and letters mean on your eyeglass prescription?

Deciphering your prescription helps give you valuable information about your vision and overall eye health. We decode it for you below.

An eye prescription is merely an equation, and your eye doctor’s exam results balance that equation to create the best possible pair of lenses for your eyes.

Your eyeglasses prescription is written in a grid using a combination of numbers and abbreviations, many derived from Latin terms pertaining to the eyes.

  • OD = Oculus Dexter, which means “right eye.”
  • OS = Oculus Sinister, which means “left eye.”
  • OU = Oculus Uterque, meaning both eyes.
  • SPH = Sphere, which refers to the lens power you’ll need to achieve 20/20, or optimal, vision. A minus sign means you are nearsighted; a plus sign mean you are farsighted. The higher the number, the more correction you need.
  • CYL = Cylinder, which represents the amount of lens power you need to correct for astigmatism, a condition where the cornea is irregularly shaped (like a football [oval] instead of a basketball [spherical]), causing blurring or distorted vision at any distance. Astigmatism is a common condition, usually present from birth.
  • AXIS = The degree, or direction, of your astigmatism. The axis number is between 1 – 180, indicating the “meridian” of your eye. This number indicates where on your lens the astigmatism correction should be located.
  • ADD = Addition, meaning the additional correction you need for reading, over your distance prescription. If you only need glasses to correct nearsightedness or farsightedness – and not for reading – you likely will not have this prescription.
  • PRISM = Some eyeglasses have a prism added when your eyes are not properly aligned, but this is not a common problem.

It is important to note that an eyeglass prescription is different than a contact lens prescription. Eyeglass lenses are positioned at a distance from the eyes, while contact lenses rest directly on the eye’s cornea. That difference affects the lens power, among other things, required for your eyes to focus properly.

The two prescriptions are not interchangeable.

Nearly 75% of the population needs some sort of vision correction, and the chance that you are one of them increases with age. So schedule an annual eye exam as part of your routine health care, to make sure your eye prescription is up-to-date and providing you with the best lenses for your vision. Life looks so much better in focus!

We value our long-term family relationships and are proud of our satisfied patient testimonials.

Contact us to have an Eye Associates professional take care of your eye health!

The information in this article should not be used for medical advice, diagnosis or treatment. As always, you should consult with your health care provider about your specific health needs.

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