There are several reasons you may buy your glasses online. The biggest is how much money you can save. There's just one wrinkle: You need to know your prescription before you order. Sure, you can call your optometrist to get the numbers, but maybe the office is closed. Or maybe you feel weird about asking because they'll know you're shopping elsewhere.
Thankfully, if you have a pretty basic prescription (meaning they're not bifocals, progressives or Coke-bottle lenses), there's a free tool from GlassesUSA.com that can scan your current glasses. I took it for a spin with my son's glasses and the results matched his current prescription.
And according to GlassesUSA.com, the results are "in line with the standard range of deviation as in any doctor's office" -- though this isn't meant to take the place of an eye exam. Let's talk about how it works and how to read your prescription.
How it works
If you just want a quick and easy way to find out what kind of lenses you have right now, here's how:
Step 1: Grab your current glasses, your smartphone and a credit card (or any other plastic card that's the size of a credit card -- it's used to calibrate the app, not for payment). Then, plunk down in front of your computer and point your browser to www.glassesusa.com/scan.
Step 2: Enter your phone number or email address to receive a link for the GlassesUSA app.
Step 3: Once you've installed the app, following the guided tutorial. You'll first need to scan an onscreen QR code, then hold the credit card up to the screen and scan that. From there you'll hold your glasses between the phone and the screen for various readings. It ends with a pupillary-distance (PD) scan, which rather amusingly requires you to hold the card up to your forehead.
Once the scan is done, the site will show you your prescription. (Make sure to verify its accuracy before ordering any new glasses.)
Screenshot by Rick Broida/CNETIt's a pretty simple process that takes all of about 10 minutes. When you're done, you'll be asked to create a GlassesUSA.com account, at which point you should immediately see your prescription.
And that's it! Armed with that data, you can order lenses and frames from anywhere. Just take note that the app doesn't store any of this information; if you want to retrieve it later, you'll have to sign back into your GlassesUSA.com account in a browser.
This isn't the only type of online vision tools available to you. Several brands like Warby Parker, 1-800 Contacts and LensDirect all have online eye assessments that you can use to order contacts or glasses.
Read more: Give Yourself an Eye Exam Right From Your Smartphone
If you've taken the GlassesUSA.com vision test, you know your prescription. That's the hardest step. But it's important to know what the numbers actually mean for your vision. According to the American Academy of Ophthalmology, you need to understand a couple of key points when looking at your eye prescription.
+/- signs
Next to the numbers on your prescription, there is likely a plus or a minus sign. This is a way to symbolize whether or not you are farsighted or nearsighted. Farsightedness, signified by the plus, means you can see things at a distance clearly, but things close by may be blurry. Nearsightedness, signified by the minus, indicates that you may have trouble seeing things clearly at a distance.
OS and OD
The rows may not be labeled as "right" or "left" eye, depending on how your prescription is formatted. Instead, you may see the abbreviations for O.D. or O.S.
- O.D. stands for oculus dexter, which is your right eye.
- O.S. stands for oculus sinister, which is your left eye.
SPH and CYL
Spherical correction is often abbreviated as SPH on your prescription. It describes the lens strength required to fix your vision problems. It's usually the first number on your prescription and is measured in diopters.
The next number on your prescription is the cylindrical correction or CYL. This concerns how much of an astigmatism you have. Astigmatism occurs when the cornea or lens of the eye is more curved than it should be, which results in the eye being unable to focus light properly. If you don't have astigmatism, this column will be left blank.
ADD
The ADD column of your glasses prescription indicates any additional lens power your eyes require to read comfortably. It can be used to determine the strength of separate reading glasses or create bifocals.
AXIS
If you have astigmatism, the AXIS column will determine where your astigmatism is on the cornea. It's represented by a number between one and 180 degrees.
Online vision tests are not a replacement for an eye exam
While online vision tests are a great tool to help you buy new glasses and correct your vision, they are not intended to replace a comprehensive eye exam, which does more than just give you a prescription.
To clarify the legality of this tool, we reached out to GlassesUSA.com. According to a company rep, "This service is FDA-listed and registered as a Class 1 Exempt Medical Device on the FDA Medical Device Listings. It does not provide medical advice, nor does it replace a comprehensive eye health exam by an eye care professional."
In addition to addressing and correcting vision issues, comprehensive eye exams assess for eye diseases like cataracts, glaucoma or melanomas. Per the American Optometric Association, it's essential that adults get annual, in-person eye exams to monitor the health of their eyes and vision changes.