Updated on
Vision Center is funded by our readers. We may earn commissions if you purchase something via one of our links.
In this article
If you’ve ever had an eye exam, and your doctor has determined that you will need vision correction, they may have mentioned that you have astigmatism, nearsightedness (myopia), or farsightedness (hyperopia).
They probably gave you an eyeglasses prescription that looks something like this:
These are all crucial pieces of information when it comes time to get your eyewear. (Note that this is different than a contact lens prescription). But what exactly do all these abbreviations and numbers mean?
We’ll break down your prescription step-by-step. You’ll know exactly how to read your glasses prescription, and what your prescription means by the end of this article.
You’ll typically find the abbreviates OD and OS on the left side of your prescription. These are abbreviations for the Latin terms oculus dexter and oculus sinister.
Essentially, OD means right eye, and OS means left eye.
You may also have a column labeled OU, which means oculus uterque, or both eyes.
Some eye doctors have modernized this and replaced OD with RE (right eye) and OS with LE.
Best Overall: Warby Parker
Fastest Delivery: EyeBuyDirect
Also Great: Liingo
Best Place to Buy Contacts: 1800 Contacts
Sphere, sometimes abbreviated as SPH, indicates the amount of lens power needed to correct nearsightedness or farsightedness.
It is measured in diopters, which is the unit of measurement for the refractive (light-bending) power of a lens.
If the number is negative (–), it means it is correcting nearsightedness.
If the number is positive (+) it means it is correcting farsightedness.
The term “sphere” refers to the fact that distance vision correction is spherical, or equal in all meridians of the eye.
Cylinder, abbreviated CYL, follows sphere power in your eyeglass prescription. It indicates the amount of lens power needed to correct astigmatism, measured in diopters.
If this column is blank, it means you have no astigmatism. If the number contains a minus sign (–), it means it is correcting nearsighted astigmatism. If the number has a plus sign or is positive (+), it means it is correcting farsighted astigmatism.
Astigmatism correction is not spherical. Cylindrical correction means that one meridian has no added power, while the meridian perpendicular to it has the maximum lens curvature and power added to it.
Axis refers to the lens meridian that contains no cylindrical power to correct astigmatism. The axis is labeled as a number from 1 to 180.
If a prescription includes cylinder power, it must be followed by an axis. The axis value is often preceded by an “x” when written in freehand.
The axis is always exactly 90-degrees away from the meridian that contains all of the correcting lens power for astigmatism.
Add indicates the magnifying power applied to the bottom part of bifocal, multifocal, or progressive lenses used to correct presbyopia (age-related farsightedness).
This number is always positive, even if it doesn’t have a plus sign (+) in front of it. These numbers typically are the same for both eyes and range from +0.75 to +3.00.
Prism refers to the amount of prismatic power needed to correct eye alignment problems, measured in prism diopters. This number is followed by the base direction, or thickest edge, of the prism.
This is only present if your eyes do not focus well together as a pair, such as in strabismus (eye turn).
This number will appear as a decimal (0.5) or fraction (½), followed by two letters indicating the base direction:
There may be additional information written in by your optometrist or ophthalmologist regarding your eye health.
This will usually be specific types of corrective lens recommendations such as multifocal lenses, progressives, anti-reflective coating, photochromatic, or transition lenses.
Some eyeglass prescriptions may require a PD (pupillary distance) measurement.
Remember, eyeglasses prescriptions are different than prescriptions for contact lenses. A contact lens prescription can only be obtained from a contact lens consultation and fitting.
In this article
Warby Parker has stylish, high-quality frames at affordable prices.
Liingo Eyewear is another great option to buy glasses online.
EyeBuyDirect has a wide variety of budget frames starting at $6.
1-800 Contacts is our #1 recommendation to buy contacts online.
GlassesUSA has a huge selection of contacts, glasses, & sunglasses.
All Vision Center content is medically reviewed and fact-checked by a licensed optometrist to ensure the information is factual and meets industry standards.
We have strict sourcing guidelines and only cite from recent scientific research, scholarly articles, textbooks, government agencies, optometry websites, and medical journals.