How to Read Your Glasses Prescription

So, you've just had your eyes checked and now you're staring at that little piece of paper covered in numbers and abbreviations, feeling a bit lost. Don't worry, you're not alone. Reading your eyeglasses prescription can seem like deciphering hieroglyphics at first, but fear not! We’re here to break it down for you in simple, everyday language.

OD vs OS

First things first, what do OD and OS even stand for? Well, OD is short for "oculus dexter," which is Latin for "right eye," while OS stands for "oculus sinister," or "left eye." 

Now, here's where things get interesting. Your prescription might have different numbers or strengths for your right and left eyes, and that's totally normal!

But wait, there's more! Sometimes you might also see OU on your prescription, which stands for "oculus uterque," meaning "both eyes." This indicates that the same prescription applies to both eyes, so you won't need to worry about any power imbalances throwing off your vision game.

Sphere, Cylinder, Axis

Now let’s talk about what the numbers actually mean. Your prescription is essentially a roadmap to help your optician craft the perfect lenses for your eyes. It contains a bunch of information, but the main things you'll want to focus on are:

Sphere (SPH): This indicates the amount of lens power prescribed to correct nearsightedness or farsightedness. If you see a minus sign (-), that means you're nearsighted, while a plus sign (+) means you're farsighted. The higher the number, the stronger the prescription.

Cylinder (CYL) and Axis: These values come into play if you have astigmatism, a common condition where the cornea or lens of your eye is irregularly shaped. The cylinder value indicates the degree of astigmatism, while the axis tells your optician the direction in which the astigmatism lies.

Add: This is for those of us who need reading glasses due to presbyopia, the natural aging process of the eyes. The "add" value represents the additional magnifying power needed for close-up tasks like reading.

Plano: Plano basically means that no prescription is needed for that value. So if your prescription says Plano (PL) then the value for that field should be 0.00.

DS: DS may be written on your prescription under the Cylinder value if you do not need correction for astigmatism. DS is short for “diopter sphere,” which basically means that your cornea or lens is uniformly curved.

Balance (BAL): Balance is typically used in a case where someone has low vision in one eye or complete loss of sight in one eye. If applying correction on the lens for the low vision eye isn’t going to help the vision of that eye, they may just match that lens to the other eye so the lenses match. This is often done for cosmetic purposes.

Types of Prescriptions

Single Vision

Single vision lenses are basically designed to correct one specific vision problem, whether it's nearsightedness, farsightedness, or astigmatism. So if you only need to tackle one of these problems, single vision glasses are for you.

If you are just correcting for nearsightedness, your prescription should only have a Sphere (SPH) number for one or both eyes. This may look like:

OD: SPH: -1.25 CYL: 0.00 AXI: 0

OS: SPH: -2.00 CYL: 0.00 AXI: 0

Similarly, if you’re just correcting for farsightedness and you don’t have astigmatism, your prescription should only have a Sphere (SPH) number for one or both eyes. This may look like:

OD: SPH: +2.25 CYL: 0.00 AXI: 0

OS: SPH: +2.50 CYL: 0.00 AXI: 0

Finally, if you have astigmatism, you may have up to 3 numbers for each eye on your prescription. Keep in mind that with astigmatism, you can still be nearsighted or farsighted. Again, the cylinder value indicates the degree of astigmatism, while the axis indicates the direction in which the astigmatism lies. Now, let’s look at the example below. Well, the -1.25 indicates you're nearsighted, while the -0.75 suggests you also have some astigmatism. The 79 tells us the axis of your astigmatism is at 79 degrees.

OD: SPH: -1.25 CYL: -0.75 AXI: 79

OS: SPH: -1.25 CYL: -0.75 AXI: 80

Some doctors don’t have it written down nicely in a chart, and it may just be written like this:

R: -1.25 -0.75 x 79

L: -1.25 -0.75 x 80

This is the exact same prescription as above, just in shorthand.

Readers

Next up, we've got readers – the MVPs for all you bookworms and screen-scrollers out there. These are designed for up-close tasks like reading, browsing your phone, or tinkering with tiny gadgets. Put simply - they’re magnifying glasses. You may see these all over the place at grocery stores, pharmacies, and even book stores! But if you want to order a custom pair for yourself, you’ll need a reading glasses prescription, or just to know the level of magnification you need.

For example, this will look like +2.25. This will apply this level of magnification to both eyes.

Progressives

Last but not least, we've got progressives – the ultimate multitaskers in the eyewear world. If you’ve been juggling multiple pairs of glasses for different tasks, progressives are for you. Progressives seamlessly transition between near, intermediate, and distance vision, giving you the freedom to tackle any task without missing a beat.

You’re going to want to order progressives if you have an Add value on your prescription. If you’re correcting for farsightedness, astigmatism, and need readers, you’re going to have a lot of numbers. Let’s take the example from above, and just add the readers. In that case, your prescription will look something like this:

OD: SPH: -1.25 CYL: -0.75 AXI: 79 ADD: +2.25

OS: SPH: -1.25 CYL: -0.75 AXI: 80 ADD: +2.25

Again, this means that you are nearsighted, have slight astigmatism, and need magnification for reading.

To wrap things up, here are a few extra tips about ordering eyeglasses:

1. Don't hesitate to ask your eye care professional to explain any part of your prescription that you don't understand. They're there to help!
2. Update Regularly: Your eyes change over time, so make sure to get your eyes checked and your prescription updated regularly, usually once a year.
3. Consider Your Lifestyle: If you spend a lot of time in front of screens, consider ordering blue light blocking lenses. Or if you drive a lot during the day and are nearsighted, consider ordering a pair of prescription sunglasses!

So there you have it, folks! Reading your eyeglasses prescription doesn't have to be rocket science. With a little bit of knowledge and a dash of curiosity, you'll be navigating those numbers like a pro in no time. Happy seeing!