How to read a prescription

Reviewed by : Myglassesmart on Jun 13th,2024

Why do we need eyeglass prescription?

The latest eyeglass prescription can let us know how to cut your lenses and correct your vision better. For young people under 18 years old, the prescriptions should ideally be renewed semi-annually, and once a year for adults over 18 years old. Usually, you’ll see some abbreviations and words labeling all of the most important data on your prescription, such as SPH, CYL Axis, ADD, PD, and so on.

Prescription is So Hard to Understand? NOT AT ALL!

The glasses prescription may seem difficult at first, with several abbreviations and strange words, but what you need is a little guidance, it's actually quite straightforward.

SPH, CYL, Axis, ADD and PD

1. The heading should be "Prescription" or "Rx" on your eyeglasses prescription.

2. OD and OS, which refer to your right eye (OD) and left eye (OS).

3. Sphere (sometimes abbreviated as "SPH"), Cylinder (CYL) and Axis are the three numbers that

SPH: The Sphere (SPH) value indicates the amount of lens power you need to see clearly. It can be a positive(+) or negative(-) number, which indicates whether you are nearsighted (-) or farsighted (+).

CYL: The Cylinder (CYL) and Axis values are used to correct astigmatism. The Cylinder value represents the amount of lens power needed to correct any astigmatism.

Axis: The Axis value indicates the orientation of the astigmatism.

4. ADD: ADD, or Near Addition, is the added magnifying power applied to the bottom part of Multifocal or Progressive lenses to correct presbyopia. The optometrist will measure the diopters needed to see at a distance and then the diopters needed to see close up, and the difference between them is the ADD. The ADD value is usually the same for both eyes. 

5. Pupillary distance (PD), which is the distance in millimeters between the centers of your pupils. This measurement is needed to ensure the correct placement of your lenses in your glasses frames. Mainstream is available in two forms, 1 number or 2 numbers.

Understanding Your Prescription Brings Better Vision

It's important to understand your prescription if you want to choose the right eyeglasses. If you have any questions or concerns about your prescription, don't hesitate to ask your eye doctor or us for clarification.