For anyone wondering what all the letters & numbers on their prescription mean, here's an easy-to-understand breakdown

Full disclosure: I work at GlassesUSA. Posting this because one of the most common things I see is people leaving their eye exam with a prescription they can't make sense of. I also see a lot of similar questions here, so I figured putting together a quick, plain-English cheat sheet that can help.

OD / OS: Latin for right eye (OD) and left eye (OS). Some newer prescriptions use RE/LE instead.

SPH (Sphere): The main correction number. Negative = nearsighted. Positive = farsighted. The further from zero, the stronger the prescription.

CYL (Cylinder) + Axis: These two always come as a pair and only matter if you have astigmatism (which is super common). CYL is the strength of the correction, and Axis (1-180) is just the angle the lab needs to place it. If it's blank, you don't have it. 

ADD: Only appears on progressives or bifocals. Indicates the extra magnification needed for reading. ADD is always a positive number.

PD (Pupillary Distance): The distance between your eyes so the lab knows where to center the lenses. Doctors notoriously leave this off the slip. Always ask them to write it down before you leave the office so you don't have to chase them down later. 

One thing that trips a lot of people up: your glasses prescription and contact lens prescription are not the same thing and are not interchangeable. Contacts sit directly on the eye so the numbers are calculated differently.

I kept this to the absolute basics, but there are a few outlier things people ask about that don't show up on every prescription like prism correction, plano lenses, or how a crazy high script affects your frame choices. To avoid throwing an even bigger wall of text into this sub, there’s a deeper dive if you want the advanced stuff:

How to Read Your Eyeglass Prescription

Drop any script or general eyewear questions you have below and I'll answer what I can!