Sphere, Cylinder, Axis, ADD, and so on. Oh, my gosh! Don't worry if you don't understand these words, we're here to teach you what all this means so you can read your Eyeglasses Prescription with Ease.
Usually, your glasses prescription is a series of numbers in a chart, which describe the lenses needed to correct your vision. Prescription chart has two rows, one for your right eye and one for your left. Four columns are used to precisely describe your correction.
First, you’ll notice there are a bunch of abbreviations in your prescription. Here are the definitions of abbreviations.
The medical abbreviation OD, refers to the right eye. Sometimes it is simplified to R.
The medical abbreviation OS, refers to the left eye. Sometimes it is simplified to L.
SPH or Sphere
The “spherical error” refers to correction needed for nearsighted ( - ) or farsightedness ( + ). If you have a “+” starting at beginning of your spherical error that means you need to select Reading during the Rx process. There's a “-” you're going to probably want to pick Distance unless you know you're going to order multifocal lenses. We recommend you to consult your optometrist to confirm your Prescription Type whether it is suitable for multifocal lenses (progressive lenses). Distance and Multifocal are two different prescription types. The larger the number following the +/-, the stronger the prescription.
CYL or Cylinder
Describes astigmatism, a refractive error that causes distorted and blurred vision, Cylinder refers to the amount of lens power is needed and measured in quarters and proceeded by a (+) or (-).
The axis indicates the orientation of astigmatism, measured in degrees from 1 to 180.
ADD or NV
Meaning Near Vision is used for multifocal or reading correction, measured in quarters. This power for bifocal or free-form progressive lenses enlarges immediate vision and is therefore always indicated by a positive sign (+).
PD or Pupillary Distance
Pupillary Distance or PD, refers to the distance in millimeters between the center of one pupil to the center of the other. It will determine how to place your lenses in your frame. It is pretty important. If you can’t find the number of PD in the prescription, please ask your doctor or optometrist. They should have your PD number on file. You can also measure your PD by yourself. Click HERE to know more. However, we recommend you to obtain your PD from your optometrist on priority.
Prism refers to the prismatic power used to correct vision displacement. It helps to reduce eyestrain and correct double vision.