In the example you see above, OD stands for “oculus dexter” and indicates your right eye’s parameters, while OS or “oculus sinister” shows your left eye’s parameters. The Sphere attribute measures the lens power needed to compensate for your near and farsightedness. It’s measured in diopter with a positive number indicating hyperopia (farsighted) and negative for myopia (nearsighted).
The Cylinder and Axis attributes are taken together and represent the measurements needed to correct your astigmatism. Cylinder denotes the power needed to correct the problem while Axis measures the degree of the angle the cylinder needs to be placed at on your lenses in order to align your vision. If you use bifocals, trifocals or transition lenses, the ADD field will note how much magnifying power the lenses provide at each level, typically between +.75 and +3.00 times magnification. You’ll also need to know your Pupillary Distance (PD), which is the length between the centers of your left and right pupils, measured in millimeters. This is especially important for glasses because getting that number wrong means your eyes will be off center when looking through the lenses and that’s going to degrade their corrective performance.
If you’ve been to an optometrist or ophthalmologist within the past 12-24 months and undergone an eye exam, you’re golden. The prescription is valid and you can shop for glasses online with the confidence that they’ll deliver crisp and clear optics. If your prescription is older than that, you’re going to need to bite the bullet and make an appointment for a proper exam. 29 states in the US do allow for people to renew their prescriptions online, however, the American Optometric Association argues that these tests often return inaccurate results and do not allow trained eye care professionals to check the overall health of your eyes or look for early warning signs of oncoming disease.
Now, if you don’t have your prescription handy and can’t get in touch with your optometrist but still really need a new set of glasses, don’t despair. Sites like GlassesUSA offer an app-based prescription detection service. Simply launch the app on your phone, hold your glasses in front of the phone’s camera and follow the onscreen directions. In less than 10 minutes the app will have figured out the various aspects of your prescription and logged that information into your GlassesUSA account. This should in no way replace routine in-person exams — think of it more as a stop-gap measure to get you through the quarantine because, again, there are a whole host of issues that a human optician can spot that even the most advanced computer vision systems cannot.
When shopping for frames online, be sure to have your existing glasses on hand because you’re going to need to grab three more measurements off of them. Look at the inside edge of the existing frame’s temple arm. The first number you’ll see is the lens width, measured in millimeters. That’ll be followed by a small square and the second measurement, the bridge width, again measured in millimeters. The final number is the length of the temple arm itself. Knowing these measurements will help you select your next frame by giving you an idea of what you’re already working with. If you already like the frames you’ve been wearing, these figures will give you a solid jumping off point when shopping for the new pair, especially if the online retailer you’re shopping doesn’t offer virtual, AR-based previews of what the frames will look like on your face.
Once you’ve got your measurements all squared away, the fun can begin. Online glasses retailers have been popping up in droves over the past few years and, since they don’t have to mark up their prices to subsidize a brick-and-mortar operation, you’ll likely save a bunch of money on your next set of specs.
Warby Parker is one of the biggest names in online glasses. Their frames start at $95, anti-scratch and anti-glare coatings with UV protection come standard and the company allows shoppers to try on up to five pairs at a time, for up to five days at a time, at home. You will need to give them your prescription information as well as your pupillary distance measurement for the try-at-home program, though if you don’t have your PD handy, the site offers an automated tool for measuring that on its site.
If you spend a majority of your day looking at a computer monitor or smartphone, Ambr offers a selection of blue-light filtering lenses, which help to cancel out the screen glare. Frames start at $64, though the company only offers about a dozen frame styles and the prices can quickly escalate depending on the kinds of lenses and options you select. Their glasses are available both with and without a prescription so even if your vision is fine (*shakes fist enviously*), these can help reduce your daily eye strain.
Shoppers on a budget should check out EyeBuyDirect. They offer frames for as little as $6 a pair with single-vision distance, bifocal, and progressive lenses set in frames of myriad colors, styles, and materials. However, there is a catch in that they don’t carry many designer brands (though they did start offering Oakley and RayBan this June). If you’re looking for the latest styles from Versace, look elsewhere. Nor does the company offer a try-at-home program like Warby Parker but if you spend $100 in a year with them, you’ll be enrolled with EBD’s loyalty program which offers free shipping and the occasional 15 percent off future orders.
Zenni is another budget retailer and, like EBD, if you’re looking for designer brands (or shipping that takes less than 2 – 3 weeks) this isn’t the retailer for you. What you will find however, is a wide selection of frames that run anywhere from $7 – $45.
Coastal does offer designer frames, many from some of the top brands in the industry including Versace, RayBan, Oakley, Polo and Michael Kors. Frames run anywhere from nine bucks to as high as $500, though the company does offer free shipping on orders over $50 as well as free returns.
If you’re having trouble finding a pair of glasses that captures your inner you, check out this handy guide by the Mather Vision Group which explains what frame shapes and styles work best for your facial shape.