From plus to minus - just what does your eyesight prescription mean?

Are you confused and intrigued as to what that row of numbers on your glasses prescription means? Well here is the specs123 guide to making sense of it all.


SPH is the amount that your glasses need adjusting by in order to create the most ideal vision possible.

A + indicates short sightedness, also known as myopia whereas a – means long sightedness, hyperopia. The larger the number, the bigger the correction will be with the goal being 20/20 vision.


CYL refers to the astigmatism, which in non-optical language is all about the shape of your eyeball. If your cornea is not as round as it should be, you have an astigmatism and the figures in this box are what is needed to make this better. Obviously, if there is no number in the box then you have no astigmatism.

When it comes to contact lenses, the way they sit on the eye becomes highly important to the results given. As in most areas of life, technological advances mean that more and more lenses are continually coming on to the market to help.


This is also about the astigmatism but tells the lens glasses laboratory just how to position your lenses. The number is measured in degrees and it is quite technical but essential to perfect results.


The Prism box comes into use when the eyes are not coming together as well as they should, as is in the case with double vision. Aligning lenses correctly can compensate for this. The prism position helps the light be directed optimally.


This is all about the positioning of the lens and tells the techie lab folk where the lens needs to sit, similar to the prism detailing.