How to Read a Glasses Prescription

Q: What do ‘OD’ and ‘OS’ mean?

‘OD’ and ‘OS’ are abbreviations of the Latin words ‘oculus dexter’ and ‘oculus sinister’, respectively. In the context of an eye prescription, ‘OD’ means ‘right eye’ and ‘OS’ means ‘left eye.

Q: What does Sphere, Cylinder and Axis mean?

In the context of an eye prescription. ‘Sphere’ is basically a measure of how strong your prescription needs to be. The number marked ‘axis’ describes the orientation of astigmatism. It will be a number between 1 and 180. The number under ‘cylinder’ provides the lens power needed to correct the astigmatism.

Q: What does ‘base’ mean on an eye prescription?

Your prescription may have a ‘base’ column, or it may be included in the same column as ‘prism’ this gives further information about the required prism correction, telling us the orientation needed in the lens.

Q: What does ‘add’ mean on an eye prescription?

The number under the ‘add’ column tells us the 2nd lens prescription needed for multifocal lenses.

Q: What is a strong eye prescription?

The higher the number on your prescription, the stronger your prescription is. A number with a minus symbol before it means you are nearsighted, and a number with a plus symbol, or no symbol, means you are farsighted. A number over 5 is generally considered to be on the stronger side.

Q: What is an astigmatism?

If you have an astigmatism, indicated by an “axis” and “cylinder” number on your prescription, it means that the front of your eye is irregularly shaped. This stops light from focusing properly on your retina and makes your vision blurry. It usually occurs along with near or farsightedness.

Q: Is astigmatism hereditary?

Astigmatism is often present at birth, but it can develop, or become more severe, as you get older.

Q: What is a diopter count?

Diopter is the measurement used for the strength of eyeglass lenses. The number under the ‘OD’ and ‘OS’ measurement in your prescription is measured in diopters.

Knowing how to read your eyeglass prescription is a must! You might already know if you're nearsighted, farsighted, or dealing with astigmatism, but deciphering it from that prescription slip can be a whole different ballgame. So, we've put together a quick guide to help you figure out how to read your glasses prescription and get those snazzy new eyeglasses ordered ASAP!

If you've had an eye exam and your vision needs have changed, it's crucial to get a new prescription right away. Your optometrist or ophthalmologist will provide you with the updated prescription.

Now, when you want to order glasses from online retailers, they usually ask you to input your prescription on their order form. But if you're not sure how to read your prescription, that whole process can be pretty confusing.

What do all these letters and numbers mean?

Your eyeglass prescription contains essential details for cutting your lenses just right to meet your vision needs. Make sure to keep it updated so that the numbers accurately reflect your eyesight. Your prescription will have various abbreviations and terms, like SPH, CYL, Axis, Prism, PD, and others, each representing important information about your glasses. Stay on top of it to ensure you get the best eyewear for clear vision!

OD vs. OS Eye

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.

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 ‘sphere’ box. This means your lenses will be shaped to improve your distance vision.

GLASSES PRESCRIPTION