Ask the optician – What do all the numbers on my prescription mean?

Eye Tests

REGULAR check-ups with your optician can help you to maintain clear and comfortable vision. Most people should have a full eye test every two years.

At Specsavers our opticians carry out thorough eye tests that provide professional, comprehensive checks of your eyes and vision. After your eye test, if your vision needs to be corrected with glasses or contact lenses you will be given a prescription which explains the issues with your eye sight. Here’s an explanation of what the numbers and codes on your prescription mean.

SPH (sphere) – the amount of long (+) or short (-) sight – the higher the number, the stronger the prescription lenses required.

CYL (cylinder) – the amount of astigmatism, or visual distortion, caused by an irregularly shaped cornea – the surface of the front of the eye.

AXIS – the direction of the astigmatism, measured in degrees.

PRISM – correction needed to balance the eyes

BASE – the direction of any correction needed to balance the eyes (prism)

ADD – the amount of additional correction needed to focus at close distances. If you have a measurement shown in this section of your prescription, it means that you have different prescription requirements for distance and reading.

Ask your optician in store if you have any doubts, we are here to help and are currently offering free eye tests, visit


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