Glasses versus contact lens prescriptions

And the differences between them

Is a contact lens prescription the same as a glasses prescription? The short answer: no, unfortunately they’re different. It’s counter-intuitive, but it’s true. Even though a glasses prescription and a contact lens prescription are correcting the same pair of eyes for the same adjustments, there is still an important difference between the two. There are two pieces to a contact lens prescription that separate it from a glasses prescription. 

Distances

On average, your glasses are 12 millimeters from your eye. This slight distance between your eye and the lens is accounted for in your glasses prescription.

With contacts, that distance doesn’t exist, since they sit directly on your cornea. Your contact lens measurements account for the difference in distance to make sure you have 20/20 vision.

Measurements and “My brand!”

There are additional measurements needed for a contact lens prescription: base curve and diameter. A base curve is simply the roundness of your eye and diameter is how wide across it is. Those are two very important measurements for contacts since they will dictate how comfortable a lens fits.

Base curve and diameter don’t apply to glasses since they don’t sit directly on your eye. With that in mind, your eye care provider will often have different exams to schedule when making an appointment. One for glasses and one for contacts. Be sure to schedule the correct type of exam when visiting your eye care provider.

Lastly, a contact lens prescription specifies a brand of contact lenses, whereas brand isn’t included on a glasses prescription. By law, you’re only allowed to buy the brand of contact lens you were prescribed.

Well, we hope that helps! We’re always available to answer any questions you might have over the phone, online, or on Facebook messenger.