Your Glasses Prescription Explained

confused woman wearing glasses

So you’ve just had an eye test at one of our branches.

Once you are finished with the optometrist, and our staff have talked you through our choice of frames or given you your contact lenses, they’ll hand you a copy of your prescription.

Did you leave the shop wondering what the number and symbols on your prescription card mean?

Here is your glasses prescription explained:

Your Glasses Prescription

Your prescription card will be divided into the right and left eye, as the prescription often differs between the two. You’ll be given a set of figures for both the near and long sight, if applicable. As a general rule, the further from 0 the figures, the worse the prescription.

You’ll see each eye is divided into five categories:

SPH (sphere)

This figure is an indicator of the quality of your sight.

If the figure in this box is accompanied by a “+”, you are long sighted. This means that you find it difficult to see things close up. A “-”, on the other hand, indicates that you are short sighted and have trouble seeing things far away.

The figure indicates the level of short or long-sightedness. It can be as little as 0.25, but some patients measure as much as 6.00. The higher the number, the stronger the prescription required. The higher the prescription, the greater the curve needed on the lens.

CYL (cylinder)

Next, you’ll see a box entitled CYL, for cylinder. This is an indicator of the shape of your eye. If you have an irregularly shaped cornea, this figure demonstrates the amount of astigmatism (visual distortion) in your eyes.

If there is no figure in the box, there is no astigmatism in your eye, and your eye is perfectly spherical. The higher the figure, the more oval in shape your eye. A figure of 3.00, for example, indicates that your eye is the shape of a rugby ball, rather than a football as it should be.

What is Astigmatism?




This is an indicator of the direction of the astigmatism, measured in degrees between 0 and 180. It has no bearing on your sight, but helps the technicians in our lab to know which direction to face the lenses in your new frames.



If your eyes don’t work together, then you’ll be given a PRISM figure. Sometimes there is a muscle imbalance between your eyes, which requires a corrective prism lens to prevent double vision and headaches. Again, this figure is an instruction to our technicians as to how severe a prism lens to fit.


This just tells our technicians where to put the prism in your new glasses.

We hope this has cleared up any questions you might have had about your glasses prescription. But if you have any further queries about your prescription, please do not hesitate to get in touch, or visit us in one of our branches.