Frequently asked questions
How do I read my prescription?
If you need glasses, your eye doctor will provide you with a prescription for corrective lenses. Eyeglass prescriptions may be written in different ways, though most are either printed or handwritten in horizontal rows. The first row is the prescription for the right eye (OD), and the second row is for the left eye (OS). Within each of these rows are three values: Sphere (SPH), Cylinder (CYL), and Axis. The SPH number corrects for nearsighted [indicated with a minus (-)] or farsighted [indicated with a plus (+)] vision. The CYL number and AXIS number correct for astigmatism. You may also have another field labeled as ADD which corrects for the reading power used in a bifocal or progressive lens. To learn more about how to read your prescription, click here. Lastly, eyeglass prescriptions sometimes include the pupillary distance (PD) measurement, which is the distance between your pupils. PD is needed to determine where the optical center of the lens will be for clear, accurate vision. If your prescription does not include your PD, you can measure it yourself with our guide here. An eyeglass prescription will usually expire in 1-2 years, depending on which state you received your eye exam.
What is Pupillary Distance?
Pupillary distance (PD) measures the distance between the centers of your pupils. This measurement is used to determine where you look through the lens of your glasses and should be as accurate as possible. The average adult’s PD is between 54-74 mm; kids' are between 43-58 mm. Your eye doctor will usually measure your PD during an eye exam. However, if it was not given to you, the below 5 steps will help you measure it yourself.
How to Measure Your PD?
Stand 8 in. away from a mirror.
Hold a ruler against your brow.
Close your right eye then align the ruler’s 0 mm with the center of your left pupil.
Look straight then close your left eye and open your right eye.
The mm line that lines up to the center of your right pupil is your PD.