How to read your glasses prescription

optician trying glasses on woman

by Bryony Firth-bernard |

If you’ve had your eyes tested and you need glasses your optician will give you a glasses prescription. But to us non-eye professionals this piece of paper looks rather confusing. If the weird words and number on your prescription have left you scratching your head then look no further, as we breakdown what they mean so you know exactly how to read your glasses prescription.

How to read your glasses prescription

Below is what your glasses prescription may look like. Every one will have the strange lettering ‘sph’, ‘cyl’, ‘axis’, ‘prism’ and ‘base’. Below we explain what they all mean.

glasses prescription example

‘SPH’ meaning on my glasses prescription

This stands for ‘sphere’ and refers to the strength of your lens. In this box will be a number and it’s usually different for each eye. If there’s a ‘+’ sign in this box it means you’re long-sited, so you struggle to see things close to you. If there’s a ‘-’ sign it means that you’re short-sighted and you struggle to see things far away from you. The number could start from something small (like 0.25) or be bigger (such as 6.00) - the higher the number, the stronger prescription is needed.

‘CYL’ meaning on glasses prescription

This stands for ‘cylinder’. If you have astigmatism there will be a number in this box, but if you don’t then there won't. Astigmatism is when your eye is shaped more like a rugby ball, as opposed to a football, which causes light to be focused at more than one point of the eye. It can lead to blurred vision and headaches. The number in this box refers to how much lens power is required to correct this issue. The lower the number, the more round your eyes are and the higher the number, the more oval shaped they are.

‘AXIS’ meaning on glasses prescription

This is only applicable to your prescription if you have astigmatism. It tells the optician the direction the cylindrical power needs to be placed in your lenses. The number in the box can range from one to 180 and it’s in degrees.

‘PRISM’ meaning on glasses prescription

If your eyes aren’t working well as a pair, you may need prismatic correction in your lenses. It’s rare that this box is filled in, but if it is, it’s usually in fractions. A prism will help prevent double vision and correct the imbalance.

‘BASE’ meaning on glasses prescription

This is connected to the prism part of your prescription and tells the lab where the prism needs to be placed in your lens, if needed.

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