Difference between glasses and contacts prescription

So, you’ve got a prescription for glasses, and now you’re wondering, "Can I just use this same piece of paper for contacts (spoiler alert: no.)?” But don't worry, you’re not alone. We’re here to walk you through the important, and surprisingly interesting, differences between glasses and contacts prescriptions. And no, it’s not just about the fact that one involves something resting on your nose and the other involves something you poke in your eye (with love, of course). 

Are contact prescriptions the same as glasses? 

Ah, the big question. Is your glasses prescription the same as your contact lens prescription? We hate to break it to you, but nope. It’s kind of like trying to wear your shoes as gloves (not quite right and probably uncomfortable). While both types of prescriptions are meant to help you see clearly, they take into account some pretty different factors. 

Understanding prescription fundamentals 

Let’s start with the basics. When you get a prescription for glasses, it includes a bunch of fun terms like "sphere," "cylinder," and "axis" (and no, that’s not a new yoga workout). This describes how strong your lenses need to be to correct your vision. Contact lens prescriptions, though, add in extra details like base curve and diameter. These make sure the lens fits snugly on your eyeball (because one size fits all is definitely not a thing when it comes to your eyes). 

Factors influencing prescription differences 

Contacts sit directly on your eye, whereas glasses chill out a few millimeters away on your face (which doesn’t seem like much, but in the world of optics, it’s a big deal). That little bit of distance means the power of your lenses, which is how much they bend light, has to be adjusted. Contacts also have to match the curvature of your eye, while glasses just need to fit the general shape of your face (and your personal style, of course). 

Converting contact prescription to glasses 

Now that you’re an expert in why your contact and glasses prescriptions aren’t identical (or you’ve at least nodded along), let’s get into the nitty-gritty of whether you can convert one prescription to the other. 

How prescriptions are calculated 

Converting a contact lens prescription into a glasses prescription is a little like translating languages. You can do it, but you might lose some nuance. Your eye care professional uses a formula that accounts for the distance between your glasses and your eyeballs. It’s not just a matter of swapping numbers; there’s a surprising amount of math involved. 

Considerations and limitations 

Here’s the catch: While it’s possible to convert your prescription, it’s not perfect. Factors like astigmatism (that’s when your eye is shaped a little more like a football than a basketball) can make it trickier to get an exact match. Plus, contacts move around on your eye, whereas glasses stay put, so it’s important to get each prescription just right for the best results. 

Can I use my glasses prescription for contacts? 

Using your glasses prescription to order contacts can lead to all kinds of discomfort (and who wants itchy, dry eyes?). Worse, it can cause your vision to be blurry or distorted. We know it might feel like a hassle to get a separate contact lens prescription, but trust us, it’s worth it. 

Getting the right prescription 

If you’re ready to get a contact lens prescription, all it takes is a professional eye exam. Your provider will check the fit of the lenses on your eye (remember that base curve we talked about?) and make sure your prescription is accurate. Once that’s done, you’ll be good to go with clear vision and happy eyes!