Trying to read a glasses prescription can be confusing so we wanted to share a few tips with you when trying to understand your prescription before you order your new glasses! On your prescription you will have a Sphere (the strength of the lens you need), a Cylinder (the lens power needed to correct astigmatism), and an Axis (the spot where we place the lens correction for astigmatism), and sometimes the Pupillary Distance (PD) if your doctor included it.
SINGLE VISION PRESCRIPTIONS
The most common prescription format is in the way of a grid with clearly printed fields for OD, OS, SPH, CYL, etc. like in the sample above.
1. Right Eye (OD), Left Eye (OS)
OD and OS are Latin abbreviations for right eye (oculus dexter) and left eye (oculus sinister). Some doctors may use OU to reference both eyes. And sometimes you will see RE and LE for right eye and left eye respectively.
2. Sphere (SPH) aka Power (PWR)
The Sphere number refers to the lens power needed for each eye. A minus (-) is used to correct nearsightedness, and a plus (+) sign next to the number is used for farsightedness. If there is "Plano" or "PL" in the Sphere section of your prescription, it means no nearsighted or farsighted correction is needed.
3. Cylinder (CYL)
Cylinder is the lens power needed to correct astigmatism. If you have no astigmatism, this column will be blank. A nearsighted astigmatism will have a minus (-) before the number, and a farsighted astigmatism with have a plus (+) sign. If there is "DS" or "Sph" or "Spherical" in the Cylinder section of your prescription, it means no correction is needed.
4. Axis (Ax)
Like Cylinder, Axis only applies to astigmatism prescriptions. The Axis number refers to angle degrees (1 to 180). If your prescription includes Cylinder lens power, it must include Axis as well.
5. Pupillary Distance (PD)
Pupillary distance measures the distance between your pupils. We need your PD to ensure that your glasses are customized to fit you (or your child) perfectly! We can't process your prescription without this number.
Child Single PD Range: 35 - 65 mm
Adult Single PD Range: 50 - 80 mm
PD is measured in mm and can be written as a Single PD like 42, or a Dual PD like 22/20. The first number in Dual PD is the right eye (OD), and the second is the left eye (OS). 
ONLINE PD MEASUREMENT TOOL
If the PD is not included in your prescription, we have two options for you! You can easily measure it with our free Online PD Tool. Just follow the steps on screen and it will take a picture of your eyes and measure your PD for you.
If your little squirmy wormy can't sit still long enough for the online tool (we totally get it!) then you can just take a picture at home and email it to us and we'll measure the PD for you. You can follow these simple directions:
AT HOME FRAME TRY ON KIT
If you have purchased our home try on kit, then you might have noticed our cute little Happy Potamus Measurement Card in your box! You can also use this card to email us a photo to measure your PD.
Our home try on kits let you try on our variety of styles and sizes from the comfort of home to make sure you get the perfect fit before you make your purchase! Then just return the kit when you're done and place your order.
WHO IS HAPPY POTAMUS?
Our adorable company mascot, Happy Potamus, is a super fan of all things Roshambo! This plucky, potbellied pachyderm is just as tough and rugged as our unbreakable frames, but our glasses are (luckily) 1,000,000x lighter.
Happy can be found around our website wearing a variety of our glasses styles and colors, just like you can! Our frames are interchangeable so your kids can also change out their color whenever they want too!
