eyeglass prescription

How to Read Your Eyeglasses Prescription

You’ve gone to the optometrist, had your eye exam, and now it’s time to get your prescription. When you look at it, though, you’re perplexed—what do all these letters and numbers mean? How do they tell you what kind of glasses you should get? How to Read your Eyeglasses Prescription?

 

Not to worry. Eye prescriptions can be confusing, but we’ll explain all of their different parts so you know how to read one. Not only will it help you understand your eyewear better, it also makes for an extremely practical party trick. 

 

Your eyeglass prescription includes specific terms and numbers that indicate the corrections needed for your vision:

  • OD, OS, and OU
    • OD (Oculus Dexter): Information for your right eye.
    • OS (Oculus Sinister): Information for your left eye.
    • OU (Oculus Uterque): Refers to both eyes.
  • SPH (Sphere) Indicates the lens power required to correct your vision:
    • Nearsighted (Myopia): Marked with a minus (-) sign. Difficulty focusing on distant objects.
    • Farsighted (Hyperopia): Marked with a plus (+) sign. Difficulty focusing on close objects.
       
  • CYL (Cylinder) Specifies the lens power needed to correct astigmatism (difficulty focusing due to irregular cornea shape):
    • Nearsighted Astigmatism: Marked with a minus (-) sign.
    • Farsighted Astigmatism: Marked with a plus (+) sign.
       
  • AXIS Defines the orientation of astigmatism correction:
    • Measured in degrees, ranging from 0 to 180.
    • This specifies the exact position of the astigmatism on your eye.
       
  • ADD (Addition)
    • Indicates additional lens power for reading or bifocal/varifocal glasses:
    • Shows how much magnification is needed for close-up tasks or intermediate distances.
       
  • PRISM Used to correct conditions like a lazy eye or squint:
    • This adjustment shifts the focus of the lens to align the image properly on the retina.
    • Included in prescriptions for special vision needs.

 

Eye Prescription Scale

Diopters: Any numbers you see in the “Sphere” or “Cyl” column of your eye prescription stand for diopters. A diopter is a unit of measurement, like a gram or an ounce. Instead of measuring mass, however, diopters measure the refractive power of a lens. You’ll see larger numbers (more optical power!) if your prescription is higher and lower numbers if your vision doesn’t need as much help from glasses or contacts. 

 

It’s important to note that these numbers proceed in either direction on a number line—they can be positive or negative, based on the type of refractive error in your eye. If you don’t need glasses at all, you wouldn’t need any optical power from lenses: 0 diopters.

 

Negative Numbers: If you see a minus sign in front of a number, that indicates nearsightedness, or myopia. Someone with -3 diopters of nearsightedness, for example, might have trouble reading words on a chalkboard from far away. 

 

Positive Numbers: If you see a plus sign in front of a number, that indicates diopters that will correct farsightedness, or hyperopia. Someone with +3 diopters of farsightedness, for example, might struggle to read text that’s very close to their face. 
 

Expiration Date: Your eye prescription probably won’t be the same forever—it’s important to have your eyes examined regularly to make sure they’re seeing as best as they possibly can.

 

Eye prescriptions are normally valid for a year or two before they expire (the exact time period can vary depending on state laws). After that, you’ll need to renew it by scheduling an eye exam. Hope this will help you learn How to Read your Eyeglasses Prescription?

 

View our collection of Prescription Designer glasses and Prescription safety glasses.

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Frequently asked questions

Have questions? We’re here to help

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How do I read my eyeglass prescription?

An eyeglass prescription includes several measurements that help create lenses customized for your vision. Common abbreviations include OD (right eye), OS (left eye), SPH (sphere), CYL (cylinder), AXIS, ADD, and sometimes PD (pupillary distance). Each value tells your optician how to correct your vision.

What do OD and OS mean?

  • OD (Oculus Dexter): Your right eye.
  • OS (Oculus Sinister): Your left eye.
  • OU (Oculus Uterque): Refers to both eyes.

These abbreviations identify which prescription values belong to each eye.

What does SPH (Sphere) mean?

The Sphere (SPH) value indicates the amount of lens power needed to correct nearsightedness or farsightedness.

  • A minus (-) number corrects nearsightedness (myopia).
  • A plus (+) number corrects farsightedness (hyperopia).

The higher the number, the stronger the prescription.

What does CYL (Cylinder) mean?

Cylinder (CYL) measures the amount of astigmatism you have. If this section is blank, you may not have astigmatism. The CYL value works together with the Axis measurement to provide clear vision.

What does AXIS mean?

The Axis is measured from 1 to 180 degrees and indicates the orientation of your astigmatism correction. It only appears on prescriptions that include a Cylinder (CYL) value.

What does ADD mean?

ADD is the additional magnifying power prescribed for reading or close-up work. It is commonly included on bifocal, trifocal, and progressive lens prescriptions for people with presbyopia.

What is PD (Pupillary Distance)?

Pupillary Distance (PD) is the distance between the centers of your pupils, measured in millimeters. This measurement helps ensure your lenses are positioned correctly for the clearest and most comfortable vision.

Can I order glasses if my prescription doesn't include PD?

Yes, but you'll need your PD before your glasses can be made accurately. You can request this measurement from your eye care provider or measure it using a PD ruler or digital measurement tool if appropriate.

Can I use my contact lens prescription to order glasses?

No. Contact lens prescriptions and eyeglass prescriptions are different. Contact lenses sit directly on the eye, while eyeglass lenses sit in front of your eyes, requiring different measurements and lens powers.

Can VS Eyewear help me understand my prescription?

Yes. If you're unsure how to interpret your prescription, the optical experts at VS Eyewear are happy to help explain your prescription values, recommend appropriate lens options, and guide you through selecting the right eyeglasses, prescription safety glasses, sunglasses, or replacement lenses.