If you’re a patient at Leightons, you’ll have been given a prescription at the end of your eye exam. This is a document that explains in numerical terms how the lenses of your new glasses or contact lenses must be made to allow you to see clearly when wearing them.

It’s important to understand the different abbreviations, numbers, and symbols that appear on an eye prescription so you can make informed decisions when purchasing new frames or contacts. It’s also a good idea to keep a copy of your prescription in a safe place.

The first section is known as sphere (SPH), and it indicates the strength of the lenses needed to correct your vision. If you see a number with a negative sign (-), it means that you are nearsighted and will need stronger glasses or contacts than if the number had a positive sign (+).

In addition to sphere, your eye prescription may also have diopters, which measure the refractive power of the lenses needed to correct your vision. The higher the number, the stronger the correction.

Astigmatism is another common vision problem that can be accounted for on an eye prescription. It’s a condition in which the cornea isn’t perfectly spherical and results in blurred vision.

It’s not uncommon to see a separate field on an eye prescription, called cylindrical (CYL), which marks the lens power specifically for the correction of astigmatism. If the doctor makes no CYL entry, it means that the astigmatism is minor and won’t need to be corrected.