After years of putting it off, you finally make an appointment to have your eyes checked. The exam goes smoothly until your optometrist hands over your eyeglass prescription.
So many boxes. So many numbers. You smile sheepishly and shuffle off to purchase your glasses.
Don’t worry. You aren’t an optometrist, and unless you’ve studied how to interpret eyeglass prescriptions, it is completely normal to feel lost. We’ll help you crack the code and figure out what “SPH” actually means (along with the rest of the numbers and symbols).
Eyes and Their Meridians
Before we dissect your eyeglass prescription, let’s talk about your eye meridians. Your optometrist uses devices to measure the curvature of your eyes and the position of your pupils.
If you were to picture your eye with a protractor on top of the surface, the 90-degree line would represent the vertical meridian of your eye. The 180-degree line would indicate the horizontal meridian.
Lenses are prescribed to correct issues with the meridian (normally for astigmatism); however, the spherical correction of your lenses will also pertain to the meridian.
What Does SPH Actually Mean?
The good news is, the information on your eyeglass prescription makes a lot of sense once you understand all the acronyms. SPH, for example, stands for “sphere.”
The sphere number on your prescription indicates the strength of the lenses needed to correct your vision. The number is “spherical” because it is equal in both meridians of each eye.
What About Those Plus and Minuses?
Plus (+) and minuses (-) that precede the numbers in the boxes on your eyeglass prescription tell your lens manufacturer the exact strength needed for your lenses.
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Farsightedness. A plus sign indicates farsightedness. This means you can easily see objects that are far away, but you need help focusing on objects that are close up (like text in a book).
Some farsightedness is age-related. As we get older, it becomes more difficult for our eyes to focus on things that are close up. This is one of the main reasons people begin to see an eye doctor.
- Nearsightedness. A minus sign indicates nearsightedness. This means you are able to see objects close up but get a little blurry with objects that are at a distance.
You can have both nearsighted and farsighted correction on your lenses (we’ll talk about it when we discuss “ADD” below).
OD vs. OS vs. OU
Your prescription may have a dedicated column for these two-letter abbreviations, or your doctor may write them inside some of the other boxes. These help your eyeglass manufacturer know which lens needs what correction.
Because our two eyes aren’t exactly alike, it’s very common for one eye to need a different strength lens than the other. These abbreviations help your doctor communicate this info with your lens crafter.
- OD. This stands for oculus dexter. It refers to your right eye.
- OS. This means oculus sinister, or your left eye.
- OU. This abbreviation is for oculus uterque, which is both eyes.
A little fun fact, when you look at your eyeglass prescription, the information you see will always be presented with OD first or right eye. This is because, during your examination, your eye doctor will examine your right eye first (because they are facing you).
Some eye doctors have begun using “LE and RE,” indicating left eye and right eye on their prescriptions. We’re definitely in favor of anything that makes eyeglass prescriptions easier for the layperson.
All About Astigmatism
Remember how we discussed the meridians of your eye? What if your meridians aren’t even? If they aren’t, you probably have astigmatism.
With astigmatism, the cornea of your eye is misshapen. Instead of being perfectly round, like a basketball, it comes to a slight point, more like a football. This causes your vision to be blurry, especially when looking at lighted objects.
The problem becomes more difficult at night. People with astigmatism may see halos around street lights or lighted safety signs if they drive at night without corrective lenses.
What Your Astigmatism Prescription Looks Like
The vision correction information on your eyeglass prescription will have more detail if your lenses need to correct astigmatism. Specifically, there will be two additional measurements on your prescription card.
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CYL. This stands for cylinder, and it refers to the strength of the lenses needed to correct your astigmatism. Unlike SPH measurement, CYL measurement will tell your eyeglass manufacturer how much curvature is needed on your lens to balance out the meridians of your eyes.
Only one meridian will be adjusted to fix your astigmatism.
The CYL measurement will also have a plus or minus sign. This will indicate whether or not you have nearsighted astigmatism or farsighted astigmatism.
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AXIS. Remember that only one meridian is adjusted to fix astigmatism. The AXIS measure gives the value of the lens that is meridian that is not being adjusted. The AXIS measure will be 90 degrees away from the CYL measurement.
AXIS numbers fall between 1-180 and always accompany a CYL measure.
Extra Features
If you have additional vision correction issues, you will also find information about those on your eyeglass prescription.
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ADD. If you need multifocal lenses, it means you need both nearsighted and farsighted vision correction. This will be indicated by a number in the ADD column of your eyeglass prescription.
ADD means the additional lens power needed to correct age-related farsightedness. This correction will be placed on the bottom portion of your lenses and will have a plus sign.
- PRISM. This is a rare prescription, but it is used for prismatic lenses. If you have eye alignment problems, you may suffer from double vision. Prismatic glasses can correct double vision.
You may also see notes from your doctor about special eyeglass coatings, like blue light protection, anti-fog, or anti-glare.
Other Facts About Your Script
Just so you know, your eye doctor is required to give you a copy of your prescription. The FTC mandates your doctor to hand over your prescription under the Prescription Release Rule. This rule was enacted so you can shop for your frames and lenses wherever you’d like.
Also, if you’d like to switch to contact lenses, you won’t be able to get them with the same prescription you have for eyeglasses. Let your doc know if you plan to use contacts.
What If I Need Safety Glasses?
You might have a job that requires safety goggles or just be shopping for a pair of glasses to protect your eyes while you tackle your favorite home improvements projects.
You could grab a pair of goggles and stuff them over your corrective lenses, or you could level up to a pair of safety glasses in your own, customized prescription (hint: you’ll be a lot more comfortable).
Stoggles are the only safety glasses that wear like glasses, protect like goggles, and look like your favorite pair of frames. They’re stylish and protective because there’s no reason you should have to choose one or the other.
SPH with Stoggles
If you need safety glasses, or you just want a really stylish pair of frames with your prescription lenses, Stoggles has you covered. We handle your prescription in-house, saving you time and money. It’s the easiest way to protect your eyes and retain your cool factor at the same time.
Sources:
What Is Astigmatism? | AAO.org
Complying with the Eyeglass Rule | FTC.gov
What is the difference between against-the-rule and with-the-rule astigmatism? | AAO.org