How to Read a Glasses Prescription

Knowing how to read an eyeglass prescription is essential! While you likely know whether you’re nearsighted, farsighted or have astigmatism, determining that from your prescription slip is another thing entirely. That’s why we’ve put together a short guide to help you learn how to read a glasses prescription so you can get to ordering your new set of eyeglasses as quickly as possible.

What do all these letters and numbers mean?

The numbers on your eyeglass prescription describe precisely how your glasses lenses should be cut. Keep your prescription up to date so these numbers can accurately reflect your visual needs. Typically, you’ll see several abbreviations and words labeling all of the important data on your prescription. See below to learn the meaning of SPH, CYL Axis, Prism, PD, and more.

OS and OD meaning

OD is short for the Latin term oculus dexter which means right eye.
OS is an abbreviation of the Latin oculus sinister which means left eye. You’ll often see this terms on eyeglass prescriptions.
The OU medical abbreviation is for oculus uterque in Latin which means both eyes.

Sphere, Cylinder, and Axis on Eye Prescriptions

Sphere: The sphere (SPH) on your prescription indicates the lens power you need to see clearly. A minus (-) symbol next to this number means you’re nearsighted, and a plus (+) symbol means the prescription is meant to correct farsightedness.
Cylinder: The cylinder (CYL) number indicates the lens power needed to correct astigmatism. If this column is blank, it means you don’t have an astigmatism.
Axis: An axis number will also be included if you have an astigmatism. This number shows the angle of the lens that shouldn’t feature a cylinder power to correct your astigmatism.

Nearsighted prescriptions

A nearsighted prescription will feature a number with a minus (-) symbol in the ‘SPH’ box. This means your lenses will be shaped to improve your distance vision.

Prescription

	SPH	CYL	AXIS
OD right eye
OS left eye

Pupillary Distance

Farsighted prescriptions

A prescription for someone who is farsighted will feature a number with a plus (+) symbol in the 'sphere box. Thisindicates that your lens should be shaped to correct near vision.

Prescription

	SPH	CYL	AXIS
OD right eye
OS left eye

Pupillary Distance

Astigmatism prescriptions

If you have an astigmatism, you will have a number in the ‘CYL’ column of your prescription that indicates the lens power needed to correct the astigmatism. There will also be a number in the ‘AXIS’ column that’s needed for astigmatism correction.

Prescription

	SPH	CYL	AXIS
OD right eye
OS left eye

Pupillary Distance

Now that you understand those mysterious letters and numbers, you know how to read a glasses prescription! Knowing what they mean will also help you more easily discuss your prescription with your eye care professional.

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